C 常见英文面试笔试题

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C语言英文面试题

Ⅰ.Choose the right answer (30 marks).1.Determine the output of the following statement:printf("%d", 'M' - 'N');A)'M' - 'N' B) M - NC)3 D) 12.Which of following is an illegal user-define symbol?A) scanf B) _123 C)C$ D)var3.Which statement is not a C statement?B){int a; a++;} B)z = 20, a += c;C) ;D) { ; }4. Which operator can only be applied to integers?A) %= B) /C) = D) <=5. Determine the output of the following program.void main(){int y=8,x=7;printf("%d ,%d\n", ++x, y++);}A) 7,8 B) 9,7 C) 8,8 D) 8,96. Choose the wrong definition for the character strings.A) char str[4]= “QUST”;B) char str[]= “QUST”;C) char *str= “QUST”;D) char str[]={…Q‟, …U‟, …S‟, …T‟, …\0‟};7. Determine the output of the following program.void main(){int i, j, m = 0;for(i=1；i<=15；i+=5)for(j=3；j<=19；j+=3)m++;}printf("%d\n",m);A) 12B) 15C) 18D) 258. For the 2-dimensional array int b[][3]={{1,0,-1},{10,12},{8,3,9},{0}}; the value for the b[2][1] is______.A) 8 B) 5 C)3 D) 129. In the statement while(x), choose the equivalent expression for the x.A)x==0 B)x==1 C)x!=1 D)x!=010.For the following codes: int z=5, *p=&z; the value of the *p is_______.A)the address of c B)unknown valueC)the address of p D)511. In order to assign 45 to variant a and assign 64 to variant b with the statement scanf(“%d%d”, &a, &b), which input format is correct?A) 45 64B) 45, 64C) 45;64 D) 456412. What is the byte length of the string “\t\\abcd”.A) 6 B) 7C) 8 D) 913. Determine the output of the value of b.Int a[4][2] = {1,2,3,4,5,6,7,8};b = *(*(a + 2) + 1);A) 3 B) 4 C) 5 D) 614.Determine the output of the following program:main(){int n = 8;while (n > 5){n--;printf(“%d”, n);}}A) 876 B) 765 C) 8765 D) 765415. What is the functionality of function “rewind”?A) open the file again;B) return the length of the fileC) push the pointer to the end of the fileD) push the pointer to the beginning of the fileII. Short answer questions.(30 marks)1. a. Enumerate workflow control methods in C programming language. (5marks)b.Give a simple C program to show the basic parts of a C program.(5 marks)2. a. The following program takes user input number and display themultiplication result of (num + num) in the next line on the screen, but it alway displays the wrong result. Determine where the errors are and why the programcan never give the correct result. (8 marks)#include <stdio.h>void main(){int num;printf("Enter a letter: ");scanf("%d", num);num = num * num;printf("The result of num + num is %d", &num);}b. Modify the program so it will display the proper result. (12 marks) III. Write the programs. (40 marks)1. Given an array a[9], fill a with random values, then write a sorting method tosort the data in a and display the result.. (10 marks)2. (a) Write a function named min( ) that accepts 5 integers as input , whichcalculates and returns the maximum value among them. The 5 integer numbers should be arrange into an integer array, and passed to the function min( ). (5 marks)(b) Include the function in a working program. Make sure your function iscalled from main() and correctly returns a value to main(). Display the value returned by min() in main(). (5 marks)3. Write a program that declares a single-dimensional arrays named num,. Thenumbers to be stored in num are 45, 86, 12, 37, 28, 113. Sum odds and evens separately. Finally, give the results that will be displayed on the screen. (10 marks)4. Given a function:2020,10101003102≥<≥<⎪⎩⎪⎨⎧--=x x x x x x x yWrite a program to accept the user input for x , and display the value of y .。

英语c考试试题及答案

英语c考试试题及答案英语C考试试题及答案一、听力理解（共20分）1. 根据所听对话，选择正确答案。

A. 他正在图书馆。

B. 他正在回家的路上。

C. 他在等公交车。

[答案] A2. 根据所听短文，回答以下问题：问题：What is the main idea of the passage?A. The importance of education.B. The benefits of exercise.C. The advantages of technology.[答案] C二、阅读理解（共30分）阅读下面的短文，然后回答问题。

Passage 1The Internet has changed the way we live and work. It has made communication faster and more convenient.问题1：What has the Internet changed?[答案] The way we live and work.问题2：What is the effect of the Internet on communication? [答案] It has made communication faster and more convenient.Passage 2Traveling is a great way to relax and learn about different cultures.问题1：Why is traveling considered great?[答案] It is a way to relax and learn about different cultures.问题2：What can you learn from traveling?[答案] Different cultures.三、完形填空（共20分）阅读下面的短文，从所给的选项中选择最佳答案填空。

C语言笔试面试英语版

General Questions1.Does C# support multiple-inheritance?No.2.Who is a protected class-level variable available to?It is available to any sub-class (a class inheriting this class).3.Are private class-level variables inherited?Yes, but they are not accessible. Although they are not visible or accessible via theclass interface, they are inherited.4.Describe the accessibility modifier “protected internal”.It is available to classes that are within the same assembly and derived from thespecified base class.5.What’s the top .NET class that everything is derived from?System.Object.6.What does the term immutable mean?The data value may not be changed. Note: The variable value may be changed, butthe original immutable data value was discarded and a new data value was created in memory.7.What’s the difference between System.String and System.Text.StringBuilderclasses?System.String is immutable. System.StringBuilder was designed with the purpose ofhaving a mutable string where a variety of operations can be performed.8.What’s the advantage of using System.Text.StringBuilder over System.String?StringBuilder is more efficient in cases where there is a large amount of stringmanipulation. Strings are immutable, so each time a string is changed, a newinstance in memory is created.9.Can you store multiple data types in System.Array?No.10.What’s the difference between the System.Array.CopyTo() andSystem.Array.Clone()?The Clone() method returns a new array (a shallow copy) object containing all theelements in the original array. The CopyTo() method copies the elements into another existing array. Both perform a shallow copy. A shallow copy means the contents(each array element) contains references to the same object as the elements in theoriginal array. A deep copy (which neither of these methods performs) would create a new instance of each element's object, resulting in a different, yet identacle object.11.How can you sort the elements of the array in descending order?By calling Sort() and then Reverse() methods.12.What’s the .NET collection class that allows an element to be accessed usinga unique key?HashTable.13.What class is underneath the SortedList class?A sorted HashTable.14.Will the finally block get executed if an exception has not occurred?Yes.15.What’s the C# syntax to catch any possible exception?A catch block that catches the exception of type System.Exception. You can also omitthe parameter data type in this case and just write catch {}.16.Can multiple catch blocks be executed for a single try statement?No. Once the proper catch block processed, control is transferred to the finally block (if there are any).17.Explain the three services model commonly know as a three-tier application.Presentation (UI), Business (logic and underlying code) and Data (from storage orother sources).Class Questions1.What is the syntax to inherit from a class in C#?Place a colon and then the name of the base class.Example: class MyNewClass : MyBaseClass2.Can you prevent your class from being inherited by another class?Yes. The keyword “sealed” will prevent the class from being inherited.3.Can you allow a class to be inherited, but prevent the method from beingover-ridden?Yes. Just leave the class public and make the method sealed.4.What’s an abstract class?A class that cannot be instantiated. An abstract class is a class that must be inheritedand have the methods overridden. An abstract class is essentially a blueprint for aclass without any implementation.5.When do you absolutely have to declare a class as abstract?1. When the class itself is inherited from an abstract class, but not all base abstractmethods have been overridden.2. When at least one of the methods in the class is abstract.6.What is an interface class?Interfaces, like classes, define a set of properties, methods, and events. But unlikeclasses, interfaces do not provide implementation. They are implemented by classes, and defined as separate entities from classes.7.Why can’t you specify the accessibility modifier for methods inside theinterface?They all must be public, and are therefore public by default.8.Can you inherit multiple interfaces?Yes. .NET does support multiple interfaces.9.What happens if you inherit multiple interfaces and they have conflictingmethod names?It’s up to you to implement the method inside your own class, so implementation isleft entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.To Do: Investigate10.What’s the difference between an interface and abstract class?In an interface class, all methods are abstract - there is no implementation. In anabstract class some methods can be concrete. In an interface class, no accessibilitymodifiers are allowed. An abstract class may have accessibility modifiers.11.What is the difference between a Struct and a Class?Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.Method and Property Questions1.What’s the implicit name of the parameter that gets passed into the setmethod/property of a class?Value. The data type of the value parameter is defined by whatever data type theproperty is declared as.2.What does the keyword “virtual” declare for a method or property?The method or property can be overridden.3.How is method overriding different from method overloading?When overriding a method, you change the behavior of the method for the derivedclass. Overloading a method simply involves having another method with the samename within the class.4.Can you declare an override method to be static if the original method is notstatic?No. The signature of the virtual method must remain the same. (Note: Only thekeyword virtual is changed to keyword override)5.What are the different ways a method can be overloaded?Different parameter data types, different number of parameters, different order ofparameters.6.If a base class has a number of overloaded constructors, and an inheritingclass has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?Yes, just place a colon, and then keyword base (parameter list to invoke theappropriate constructor) in the overloaded constructor definition inside the inheritedclass.Events and Delegates1.What’s a delegat e?A delegate object encapsulates a reference to a method.2.What’s a multicast delegate?A delegate that has multiple handlers assigned to it. Each assigned handler (method)is called.XML Documentation Questions1.Is XML case-sensitive?Yes.2.W hat’s the difference between // comments, /* */ comments and ///comments?Single-line comments, multi-line comments, and XML documentation comments.3.How do you generate documentation from the C# file commented properlywith a command-line compiler?Compile it with the /doc switch.Debugging and Testing Questions1.What debugging tools come with the .NET SDK?1. CorDBG – command-line debugger. To use CorDbg, you must compile the originalC# file using the /debug switch.2. DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR.2.What does assert() method do?In debug compilation, assert takes in a Boolean condition as a parameter, and showsthe error dialog if the condition is false. The program proceeds without anyinterruption if the condition is true.3.What’s the difference between the Debug class and Trace class?Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.4.Why are there five tracing levels in System.Diagnostics.TraceSwitcher?The tracing dumps can be quite verbose. For applications that are constantly running you run the risk of overloading the machine and the hard drive. Five levels rangefrom None to Verbose, allowing you to fine-tune the tracing activities.5.Where is the output of TextWriterTraceListener redirected?To the Console or a text file depending on the parameter passed to the constructor.6.How do you debug an Web application?Attach the aspnet_wp.exe process to the DbgClr debugger.7.What are three test cases you should go through in unit testing?1. Positive test cases (correct data, correct output).2. Negative test cases (broken or missing data, proper handling).3. Exception test cases (exceptions are thrown and caught properly).8.Can you change the value of a variable while debugging a C# application?Yes. If you are debugging via Visual , just go to Immediate window. and Database Questions1.What is the role of the DataReader class in connections?It returns a read-only, forward-only rowset from the data source. A DataReaderprovides fast access when a forward-only sequential read is needed.2.What are advantages and disadvantages of Microsoft-provided data providerclasses in ? data provider is high-speed and robust, but requires SQL Serverlicense purchased from Microsoft. is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix. is a .NET layer on top of the OLE layer, so it’s not as fastest and efficient as .3.What is the wildcard character in SQL?Let’s say you want to query database with LIKE for all employees whose name startswith La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.4.Explain ACID rule of thumb for transactions.A transaction must be:1. Atomic - it is one unit of work and does not dependent on previous andfollowing transactions.2. Consistent - data is either committed or roll back, no “in-between” case wheresomething has been updated and something hasn’t.3. Isolated - no transaction sees the intermediate results of the currenttransaction).4. Durable - the values persist if the data had been committed even if the systemcrashes right after.5.What connections does Microsoft SQL Server support?Windows Authentication (via Active Directory) and SQL Server authentication (viaMicrosoft SQL Server username and password).6.Between Windows Authentication and SQL Server Authentication, which oneis trusted and which one is untrusted?Windows Authentication is trusted because the username and password are checkedwith the Active Directory, the SQL Server authentication is untrusted, since SQLServer is the only verifier participating in the transaction.7.What does the Initial Catalog parameter define in the connection string?The database name to connect to.8.What does the Dispose method do with the connection object?Deletes it from the memory.To Do: answer better. The current answer is not entirely correct.9.What is a pre-requisite for connection pooling?Multiple processes must agree that they will share the same connection, where everyparameter is the same, including the security settings. The connection string must be identical.Assembly Questions1.How is the DLL Hell problem solved in .NET?Assembly versioning allows the application to specify not only the library it needs torun (which was available under Win32), but also the version of the assembly.2.What are the ways to deploy an assembly?An MSI installer, a CAB archive, and XCOPY command.3.What is a satellite assembly?When you write a multilingual or multi-cultural application in .NET, and want todistribute the core application separately from the localized modules, the localizedassemblies that modify the core application are called satellite assemblies.4.What namespaces are necessary to create a localized application?System.Globalization and System.Resources.5.What is the smallest unit of execution in .NET?an Assembly.6.When should you call the garbage collector in .NET?As a good rule, you should not call the garbage collector. However, you could call the garbage collector when you are done using a large object (or set of objects) to forcethe garbage collector to dispose of those very large objects from memory. However,this is usually not a good practice.7.How do you convert a value-type to a reference-type?Use Boxing.8.What happens in memory when you Box and Unbox a value-type?Boxing converts a value-type to a reference-type, thus storing the object on theheap. Unboxing converts a reference-type to a value-type, thus storing the value onthe stack.Again some general questions.1.Explain the differences between Server-side and Client-side code?ANS: Server side code will execute at server end all the business logic will execute at server end where as client side code will execute at client side at browser end.2.What type of code (server or client) is found in a Code-Behind class?ANS : Server side.3. Should validation (did the user enter a real date) occur server-side or client-side? Why?ANS : client side . there is no need to go to validate user input. If it relates to data base validation we need to validate at server side.4.What does the "EnableViewState" property do? Why would I want it on or off?ANS: IT keeps the data of the control during post backs.if we turn off the values should not populate during server round trip.5.What is the difference between Server.Transfer and Response.Redirect? Why would Ichoose one over the other?ANS: Server.Trnasfer will prevent round trip. it will redirect pages which or in the same directory. NO way to pass the query strings . Thru http context we can able to get the previous page control values.Response.Redirect : There is a round trip to process the request. We can redirect to any page external / internal other than aspx. We can pass the query string thru which we can manage sessions.6.Can you give an example of when it would be appropriate to use a web service as opposedto a non-serviced .NET componentANS : Web services are best suite for Hetrogenious environment.Remoting is best suite for Homogenious environment. The systems that under CLR.7.Let's say I have an existing application written using Visual Studio 6 (VB 6, InterDev 6)and this application utilizes Windows 2000 COM+ transaction services. How would you approach migrating thisapplication to .NETWe need to have Wrapper to communicate COM components in .net. and vis versaCCW : Com Callable wrapper.RCW : RUN time callable wrapper.8. Can you explain the difference between an Dataset and anADO Recordset?\ANS : DIsconnected architechure . Maintainace relation schemas. MUtilple table grouping.Connected one .9.Can you give an example of what might be best suited to place in the Application_Startand Session_Start subroutines?ANS: APplication_start need for global variable which are available over the application.Sesssion_Start : login dependent ( user dependent)10.If I'm developing an application that must accomodate multiple security levels thoughsecure login and my web appplication isspanned across three web-servers (using round-robbin load balancing)what would be the best approach to maintain login-in state for theusers?ANS : Database Support.or Thru state service.11.What are Web Forms? How is this technology different than what is availablethough ASP (1.0-3.0)?ANS : ASP . Interprepter.. use the script engine. Compiled.12.How does /C# achieve polymorphism?ANS : Function overloading.Operator overloading.13.Can you explain what inheritance is and an example of when you might use it?ANS : Heridity.Use the existing functionality along with its own properities.14.How would you implement inheritance using /C#?ANS: Derived Class : Basecalss : Derived Class Inherits Baseclass15.Whats an assemblyANS : A Basic unit of executable code >Which contains : Manifest - Meta dataversioning , Calture , IL, Reference16.Describe the difference between inline and code behind - which is best in a loosely coupledsolutionTightly coupled - INLINEANS: inline function bind at compile time can write in aspx page with in <% %>.17.Explain what a diffgram is, and a good use for oneANS : is an xml grammer. it talk about state of node in xml file.18.Where would you use an iHTTPModule, and what are the limitations of any approach youmight take in implementing oneANS: Preprocessing before going to IIS.19.What are the disadvantages of viewstate/what are the benefitsANS : IT can be hacked . page size is heavy.20. How would you get running in Apache web servers - why would you even do this?ANS: ---- Install Mod_AspDotNetAdd at the end of C:\Program Files\Apache Group\Apache2\conf\httpd.conf the following lines21. Whats MSIL, and why should my developers need an appreciation of it if at all?ANS : Microsoft Intermeidate lanaguage. which is the out put for all the .net supportedlanguages after comiplation will produce.Appreciation for cross language support.22. In what order do the events of an ASPX page execute. As a developer is it important toundertsand these events?ANS : INIT, PageLoad, Prerender , UNload.23.Which method do you invoke on the DataAdapter control to load your generated datasetwith data?Fill()24.Can you edit data in the Repeater control?NO25.Which template must you provide, in order to display data in a Repeater control?ITemtemplate26.How can you provide an alternating color scheme in a Repeatercontrol?AlternateItemTemplate27.What property must you set, and what method must you call in your code, in order to bindthe data from some data source to the Repeatercontrol?Datasource,DataBind28.What base class do all Web Forms inherit from?System.Web.UI.Page29.What method do you use to explicitly kill a user s session?abondon()30.How do you turn off cookies for one page in your site?disablecookies.31.Which two properties are on every validation control?control to validate, error message32.What tags do you need to add within the asp:datagrid tags to bindcolumns manually?autogenerated columns is set to false33.How do you create a permanent cookie?Cooke = new cookie().cooke.adddate.34.What tag do you use to add a hyperlink column to the DataGrid?hyper link column35.Which method do you use to redirect the user to another page without performing a roundtrip to the client?server.transfer36.What is the transport protocol you use to call a Web service SOAPhttp37.True or False: A Web service can only be written in .NETfalse38.What does WSDL stand for? webservice discription language. it is used to generate forproxy( server object)39.What property do you have to set to tell the grid which page to go to when using thePager object?Page Index.40.Where on the Internet would you look for Web services?UDDI41.What tags do you need to add within the asp:datagrid tags to bind columns manually.Autogenerate columns42.Which property on a Combo Box do you set with a column name, prior to setting theDataSource, to display data in the combo box?datatextdatavalue43.How is a property designated as read-only?get44.Which control would you use if you needed to make sure the values in two differentcontrols matched?compare filed validator45.True or False: To test a Web service you must create a windows application or Webapplication to consume this service?no46.How many classes can a single .NET DLL contain?as many as u want..47.What is serialization, how it works in .NET?The primary purpose of XML serialization in the .NET Framework is to enable theconversion of XML documents and streams to common language runtime objects and vice versa. Serialization of XML to common language runtime objects enables one to convert XML documents into a form where they are easier to process using conventionalprogramming languages. On the other hand, serialization of objects to XML facilitates persisting or transporting the state of such objects in an open, standards compliant and platform agnostic manner.48.How many array types does C# provide?Jugged array, table array, …。

C常用面试题库

C常用面试题库1.简述private、protected、public、internal修饰符的访问权限。

答.private:私有成员,在类的内部才可以访问。

protected:保护成员，该类内部和继承类中可以访问。

public:公共成员，完全公开，没有访问限制。

internal:在同一命名空间内可以访问。

2.列举页面之间传递值的几种方式。

答.1.使用QueryString,如....id=1;repone.Redirect()....2.使用Seion变量3.使用Server.Tranfer3.一列数的规则如下:1、1、2、3、5、8、13、21、34......求第30位数是多少，用递归算法实现。

答：publicclaMainCla{publictaticvoidMain(){Conole.WriteLine(Foo(30));}publictaticintFoo(inti){if(i<=0)return0;eleif(i>0&&i<=2)return1;elereturnFoo(i-1)+Foo(i-2);}}4.C#中的委托是什么？事件是不是一种委托？答：委托可以把一个方法作为参数代入另一个方法。

委托可以理解为指向一个函数的引用。

是，是一种特殊的委托5.override与重载的区别答：override与重载的区别。

重载是方法的名称相同。

参数或参数类型不同，进行多次重载以适应不同的需要Override是进行基类中函数的重写。

为了适应需要。

6.如果在一个B/S结构的系统中需要传递变量值，但是又不能使用Seion、Cookie、Application，您有几种方法进行处理？答：thi.Server.Tranfer7.请编程遍历页面上所有Te某tBo某控件并给它赋值为tring.Empty？答：foreach(Sytem.Window.Form.Controlcontrolinthi.Control){if(controliSytem.Window.Form.Te某tBo某){Sytem.Window.Form.Te某tBo某tb=(Sytem.Window.Form.Te某tBo 某)control;tb.Te某t=String.Empty;}}8.请编程实现一个冒泡排序算法？答：int[]array=newint;inttemp=0;for(inti=0;i<array.Length-1;i++){for(intj=i+1;j<array.Length;j++){if(array[j]<array){temp=array;array=array[j];array[j]=temp;}}}9.描述一下C#中索引器的实现过程，是否只能根据数字进行索引？答：不是。

CC++ 面试题集锦英文版

Part 1C/C++ Interview Questionshow do you find out if a linked-list has an end? (i.e. the list is not a cycle)You can find out by using 2 pointers. One of them goes 2 nodes each time. The second one goes at 1 nodes each time. If there is a cycle, the one that goes 2 nodes each time will eventually meet the one that goes slower. If that is the case, then you will know the linked-list is a cycle.What is the difference between realloc() and free()?The free subroutine frees a block of memory previously allocated by the malloc subroutine. Undefined results occur if the Pointer parameter is not a valid pointer. If the Pointer parameter is a null value, no action will occur. The realloc subroutine changes the size of the block of memory pointed to by the Pointer parameter to the number of bytes specified by the Size parameter and returns a new pointer to the block. The pointer specified by the Pointer parameter must have been created with the malloc, calloc, or realloc subroutines and not been deallocated with the free or realloc subroutines. Undefined results occur if the Pointer parameter is not a valid pointer.What is function overloading and operator overloading?Function overloading: C++ enables several functions of the same name to be defined, as long as these functions have different sets of parameters (at least as far as their types are concerned). This capability is called function overloading. When an overloaded function is called, the C++ compiler selects the proper function by examining the number, types and order of the arguments in the call. Function overloading is commonly used to create several functions of the same name that perform similar tasks but on different data types.Operator overloading allows existing C++ operators to be redefined so that they work on objects of user-defined classes. Overloaded operators are syntactic sugar for equivalent function calls. They form a pleasant facade that doesn‘t add anything fundamental to the language (but they can improve understandability and reduce maintenance costs).What is the difference between declaration and definition?The declaration tells the compiler that at some later point we plan to present the definition of this declaration.E.g.: void stars () //function declarationThe definition contains the actual implementation.E.g.: void stars () // declarator{for(int j=10; j > =0; j–) //function bodycout << *;cout <<>What are the advantages of inheritance?It permits code reusability. Reusability saves time in program development. It encourages the reuse of proven and debugged high-quality software, thus reducing problem after a system becomes functional.How do you write a function that can reverse a linked-list?void reverselist(void){if(head==0)return;if(head->next==0)return;if(head->next==tail){head->next = 0;tail->next = head;}else{node* pre = head;node* cur = head->next;node* curnext = cur->next;head->next = 0;cur-> next = head;for(; curnext!=0; ){cur->next = pre;pre = cur;cur = curnext;curnext = curnext->next;}curnext->next = cur;}}What do you mean by inline function?The idea behind inline functions is to insert the code of a called function at the point where the function is called. If done carefully, this can improve the application‘s performance in exchange for increased compile time and possibly (but not always) an increase in the size of the generated binary executables.Write a program that ask for user input from 5 to 9 then calculate the average#include ―iostream.h‖int main() {int MAX = 4;int total = 0;int average;int numb;for (int i=0; icout << ―Please enter your input between 5 and 9: ―;cin >> numb;while ( numb<5>9) {cout << ―Invalid input, please re-enter: ―;cin >> numb;}total = total + numb;}average = total/MAX;cout << ―The average number is: ‖ <<>return 0;}What is public, protected, private?•Public, protected and private are three access specifiers in C++.•Public data members and member functions are accessible outside the class.•Protected data members and member functions are only available to derived classes. •Private data members and member functions can‘t be accessed outside the class. However there is an exception can be using friend classes.Write a function that swaps the values of two integers, using int* as the argument type.void swap(int* a, int*b) {int t;t = *a;*a = *b;*b = t;}Tell how to check whether a linked list is circular.Create two pointers, each set to the start of the list. Update each as follows:while (pointer1) {pointer1 = pointer1->next;pointer2 = pointer2->next; if (pointer2) pointer2=pointer2->next;if (pointer1 == pointer2) {print (\‖circular\n\‖);}}OK, why does this work?If a list is circular, at some point pointer2 will wrap around and be either at the item just before pointer1, or the item before that. Either way, it‘s either 1 or 2 jumps until they meet.What is polymorphism?Polymorphism is the idea that a base class can be inherited by several classes. A base class pointer can point to its child class and a base class array can store different child class objects.What is virtual constructors/destructors?Answer1Virtual destructors:If an object (with a non-virtual destructor) is destroyed explicitly by applying the delete operator to a base-class pointer to the object, the base-class destructor function (matching the pointer type) is called on the object.There is a simple solution to this problem declare a virtual base-class destructor.This makes all derived-class destructors virtual even though they don‘t have the same name as the base-class destructor. Now, if the object in the hierarchy is destroyed explicitly by applying the delete operator to a base-class pointer to a derived-class object, the destructor for the appropriate class is called. Virtual constructor: Constructors cannot be virtual. Declaring a constructor as a virtual function is a syntax error.Answer2Virtual destructors: If an object (with a non-virtual destructor) is destroyed explicitly by applying the delete operator to a base-class pointer to the object, the base-class destructor function (matching the pointer type) is called on the object.There is a simple solution to this problem – declare a virtual base-class destructor. This makes all derived-class destructors virtual even though they don‘t have the sam e name as the base-class destructor. Now, if the object in the hierarchy is destroyed explicitly by applying the delete operator to a base-class pointer to a derived-class object, the destructor for the appropriate class is called.Virtual constructor: Constructors cannot be virtual. Declaring a constructor as a virtual function is a syntax error.Does c++ support multilevel and multiple inheritance?Yes.What are the advantages of inheritance?•It permits code reusability.•Reusability saves time in program development.•It encourages the reuse of proven and debugged high-quality software, thus reducing problem after a system becomes functional.What is the difference between declaration and definition?The declaration tells the compiler that at some later point we plan to present the definition of this declaration.E.g.: void stars () //function declarationThe definition contains the actual implementation.E.g.: void stars () // declarator{for(int j=10; j>=0; j–) //function bodycout<<‖*‖;cout<What is the difference between an ARRAY and a LIST?Answer1Array is collection of homogeneous elements.List is collection of heterogeneous elements.For Array memory allocated is static and continuous.For List memory allocated is dynamic and Random.Array: User need not have to keep in track of next memory allocation.List: User has to keep in Track of next location where memory is allocated.Answer2Array uses direct access of stored members, list uses sequencial access for members.//With Array you have direct access to memory position 5Object x = a[5]; // x takes directly a reference to 5th element of array//With the list you have to cross all previous nodes in order to get the 5th node:list mylist;list::iterator it;for( it = list.begin() ; it != list.end() ; it++ ){if( i==5){x = *it;break;}i++;}What is a template?Templates allow to create generic functions that admit any data type as parameters and return value without having to overload the function with all the possible data types. Until certain point they fulfill the functionality of a macro. Its prototype is any of the two following ones:template function_declaration; template function_declaration;The only difference between both prototypes is the use of keyword class or typename, its use is indistinct since both expressions have exactly the same meaning and behave exactly the same way. You have two pairs: new() and delete() and another pair : alloc() and free(). Explain differences between eg. new() and malloc()Answer11.) ―new and delete‖ are preprocessors while ―malloc() and free()‖ are functions. [we dont use brackets will calling new or delete].2.) no need of allocate the memory while using ―new‖ but in ―malloc()‖ we have to use ―sizeof()‖.3.) ―new‖ will initlize the new memory to 0 but ―malloc()‖ gives random value in the new alloted memory location [better to use calloc()]Answer2new() allocates continous space for the object instacemalloc() allocates distributed space.new() is castless, meaning that allocates memory for this specific type,malloc(), calloc() allocate space for void * that is cated to the specific class type pointer.What is the difference between class and structure?Structure: Initially (in C) a structure was used to bundle different type of data types together to perform a particular functionality. But C++ extended the structure to contain functions also. The major difference is that all declarations inside a structure are by default public.Class: Class is a successor of Structure. By default all the members inside the class are private. What is RTTI?Runtime type identification (RTTI) lets you find the dynamic type of an object when you have only a pointer or a reference to the base type. RTTI is the official way in standard C++ to discover the type of an object and to convert the type of a pointer or reference (that is, dynamic typing). The need came from practical experience with C++. RTTI replaces many homegrown versions with a solid, consistent approach.What is encapsulation?Packaging an object‘s variabl es within its methods is called encapsulation.Explain term POLIMORPHISM and give an example using eg. SHAPE object: If I have a base class SHAPE, how would I define DRAW methods for two objects CIRCLE and SQUARE Answer1POL YMORPHISM : A phenomenon which enables an object to react differently to the same function call.in C++ it is attained by using a keyword virtualExamplepublic class SHAPE{public virtual void SHAPE::DRAW()=0;}Note here the function DRAW() is pure virtual which means the sub classes must implement the DRAW() method and SHAPE cannot be instatiatedpublic class CIRCLE::public SHAPE{public void CIRCLE::DRAW(){// TODO drawing circle}}public class SQUARE::public SHAPE{public void SQUARE::DRAW(){// TODO drawing square}}now from the user class the calls would be likegloballySHAPE *newShape;When user action is to drawpublic void MENU::OnClickDrawCircle(){newShape = new CIRCLE();}public void MENU::OnClickDrawCircle(){newShape = new SQUARE();}the when user actually drawspublic void CANV AS::OnMouseOperations(){newShape->DRAW();}Answer2class SHAPE{public virtual Draw() = 0; //abstract class with a pure virtual method};class CIRCLE{public int r;public virtual Draw() { this->drawCircle(0,0,r); }};class SQUREpublic int a;public virtual Draw() { this->drawRectangular(0,0,a,a); }};Each object is driven down from SHAPE implementing Draw() function in its own way.What is an object?Object is a software bundle of variables and related methods. Objects have state and behavior. How can you tell what shell you are running on UNIX system?You can do the Echo $RANDOM. It will return a undefined variable if you are from the C-Shell, just a return prompt if you are from the Bourne shell, and a 5 digit random numbers if you are from the Korn shell. You could also do a ps -l and look for the shell with the highest PID. Describe PRIV ATE, PROTECTED and PUBLIC – the differences and give examples.class Point2D{int x; int y;public int color;protected bool pinned;public Point2D() : x(0) , y(0) {} //default (no argument) constructor};Point2D MyPoint;You cannot directly access private data members when they are declared (implicitly) private: MyPoint.x = 5; // Compiler will issue a compile ERROR//Nor yoy can see them:int x_dim = MyPoint.x; // Compiler will issue a compile ERROROn the other hand, you can assign and read the public data members:MyPoint.color = 255; // no problemint col = MyPoint.color; // no problemWith protected data members you can read them but not write them: MyPoint.pinned = true; // Compiler will issue a compile ERRORbool isPinned = MyPoint.pinned; // no problemWhat is namespace?Namespaces allow us to group a set of global classes, objects and/or functions under a name. To say it somehow, they serve to split the global scope in sub-scopes known as namespaces.The form to use namespaces is:namespace identifier { namespace-body }Where identifier is any valid identifier and namespace-body is the set of classes, objects and functions that are included within the namespace. For example:namespace general { int a, b; } In this case, a and b are normal variables integrated within the general namespace. In order to access to these variables from outside the namespace we have to use the scope operator ::. For example, to access the previous variables we would have to put: general::a general::bThe functionality of namespaces is specially useful in case that there is a possibility that a globalobject or function can have the same name than another one, causing a redefinition error.What do you mean by inheritance?Inheritance is the process of creating new classes, called derived classes, from existing classes or base classes. The derived class inherits all the capabilities of the base class, but can add embellishments and refinements of its own.What is a COPY CONSTRUCTOR and when is it called?A copy constructor is a method that accepts an object of the same class and copies it‘s data members to the object on the left part of assignement:class Point2D{int x; int y;public int color;protected bool pinned;public Point2D() : x(0) , y(0) {} //default (no argument) constructorpublic Point2D( const Point2D & ) ;};Point2D::Point2D( const Point2D & p ){this->x = p.x;this->y = p.y;this->color = p.color;this->pinned = p.pinned;}main(){Point2D MyPoint;MyPoint.color = 345;Point2D AnotherPoint = Point2D( MyPoint ); // now AnotherPoint has color = 345What is Boyce Codd Normal form?A relation schema R is in BCNF with respect to a set F of functional dependencies if for all functional dependencies in F+ of the form a-> , where a and b is a subset of R, at least one of the following holds:* a- > b is a trivial functional dependency (b is a subset of a)* a is a superkey for schema RWhat is virtual class and friend class?Friend classes are used when two or more classes are designed to work together and need access to each other‘s implementation in ways that the rest of the world shouldn‘t be allowed to have. In other words, they help keep private things private. For instance, it may be desirable for class DatabaseCursor to have more privilege to the internals of class Database than main() has.What is the word you will use when defining a function in base class to allow this function to be a polimorphic function?virtualWhat do you mean by binding of data and functions?Encapsulation.What are 2 ways of exporting a function from a DLL?1.Taking a reference to the function from the DLL instance.2. Using the DLL ‘s Type Library.What is the difference between an object and a class?Classes and objects are separate but related concepts. Every object belongs to a class and every class contains one or more related objects.- A Class is static. All of the attributes of a class are fixed before, during, and after the execution of a program. The attributes of a class don‘t change.- The class to which an object belongs is also (usually) static. If a particular object belongs to a certain class at the time that it is created then it almost certainly will still belong to that class right up until the time that it is destroyed.- An Object on the other hand has a limited lifespan. Objects are created and eventually destroyed. Also during that lifetime, the attributes of the object may undergo significant change.Suppose that data is an array of 1000 integers. Write a single function call that will sort the 100 elements data [222] through data [321].quicksort ((data + 222), 100);What is a class?Class is a user-defined data type in C++. It can be created to solve a particular kind of problem. After creation the user need not know the specifics of the working of a class.What is friend function?As the name suggests, the function acts as a friend to a class. As a friend of a class, it can access its private and protected members. A friend function is not a member of the class. But it must be listed in the class definition.Which recursive sorting technique always makes recursive calls to sort subarrays that are about half size of the original array?Mergesort always makes recursive calls to sort subarrays that are about half size of the original array, resulting in O(n log n) time.What is abstraction?Abstraction is of the process of hiding unwanted details from the user.What are virtual functions?A virtual function allows derived classes to replace the implementation provided by the base class. The compiler makes sure the replacement is always called whenever the object in question is actually of the derived class, even if the object is accessed by a base pointer rather than a derived pointer. This allows algorithms in the base class to be replaced in the derived class, even if users don‘t know about the derived class.What is the difference between an external iterator and an internal iterator? Describe an advantage of an external iterator.An internal iterator is implemented with member functions of the class that has items to step through. .An external iterator is implemented as a separate class that can be ―attach‖ to the object that has items to step through. .An external iterator has the advantage that many difference iterators can be active simultaneously on the same object.What is a scope resolution operator?A scope resolution operator (::), can be used to define the member functions of a class outside the class.What do you mean by pure virtual functions?A pure virtual member function is a member function that the base class forces derived classes to provide. Normally these member functions have no implementation. Pure virtual functions are equated to zero.class Shape { public: virtual void draw() = 0; };What is polymorphism? Explain with an example?“Poly‖ means ―many‖ and ―morph‖ means ―form‖. Polymorphism is the ability of an object (or reference) to assume (be replaced by) or become many different forms of object.Example: function overloading, function overriding, virtual functions. Another example can be a plus ‗+‘ sign, used for adding two integers or for using it to concatenate two strings.How can you quickly find the number of elements stored in a a) static array b) dynamic array ? Why is it difficult to store linked list in an array?How can you find the nodes with repetetive data in a linked list?Write a prog to accept a given string in any order and flash error if any of the character is different. For example : If abc is the input then abc, bca, cba, cab bac are acceptable but aac or bcd are unacceptable.Write out a function that prints out all the permutations of a string. For example, abc would give you abc, acb, bac, bca, cab, cba. You can assume that all the characters will be unique.What‘s the output of the following program? Why?#includemain(){typedef union{int a;char b[10];float c;}Union;Union x,y = {100};x.a = 50;strcpy(x.b,\‖hello\‖);x.c = 21.50;printf(\‖Union x : %d %s %f \n\‖,x.a,x.b,x.c );printf(\‖Union y :%d %s%f \n\‖,y.a,y.b,y.c);}Given inputs X, Y, Z and operations | and & (meaning bitwise OR and AND, respectively)What is output equal to inoutput = (X & Y) | (X & Z) | (Y & Z)Why are arrays usually processed with for loop?The real power of arrays comes from their facility of using an index variable to traverse the array, accessing each element with the same expression a[i]. All the is needed to make this work is a iterated statement in which the variable i serves as a counter, incrementing from 0 to a.length -1. That is exactly what a loop does.What is an HTML tag?An HTML tag is a syntactical construct in the HTML language that abbreviates specific instructions to be executed when the HTML script is loaded into a Web browser. It is like a method in Java, a function in C++, a procedure in Pascal, or a subroutine in FORTRAN.What problems might the following macro bring to the application?#define sq(x) x*xAnything wrong with this code?T *p = new T[10];delete p;Everyt hing is correct, Only the first element of the array will be deleted‖, The entire array will be deleted, but only the first element destructor will be called.Anything wrong with this code?T *p = 0;delete p;Yes, the program will crash in an attempt to delete a null pointer.How do you decide which integer type to use?It depends on our requirement. When we are required an integer to be stored in 1 byte (means less than or equal to 255) we use short int, for 2 bytes we use int, for 8 bytes we use long int.A char is for 1-byte integers, a short is for 2-byte integers, an int is generally a 2-byte or 4-byte integer (though not necessarily), a long is a 4-byte integer, and a long long is a 8-byte integer. What‘s the best way to declare and define global vari ables?The best way to declare global variables is to declare them after including all the files so that it can be used in all the functions.What does extern mean in a function declaration?Using extern in a function declaration we can make a function such that it can used outside the file in which it is defined.An extern variable, function definition, or declaration also makes the described variable or function usable by the succeeding part of the current source file. This declaration does not replace the definition. The declaration is used to describe the variable that is externally defined.If a declaration for an identifier already exists at file scope, any extern declaration of the same identifier found within a block refers to that same object. If no other declaration for the identifier exists at file scope, the identifier has external linkage.What can I safely assume about the initial values of variables which are not explicitly initialized? It depends on complier which may assign any garbage value to a variable if it is not initialized. What is the difference between char a[] = ―string‖; and char *p = ―string‖;?In the first case 6 bytes are allocated to the variable a which is fixed, where as in the second case if *p is assigned to some other value the allocate memory can change.What‘s the auto keyword good for?Answer1Not much. It declares an object with automatic storage duration. Which means the object will be destroyed at the end of the objects scope. All variables in functions that are not declared as static and not dynamically allocated have automatic storage duration by default.For exampleint main(){int a; //this is the same as writing ―auto int a;‖}Answer2Local variables occur within a scope; they are ―local‖ to a function. They are often called automatic variables because they automatically come into being when the scope is entered and automatically go away when the scope closes. The keyword auto makes this explicit, but local variables default to auto auto auto auto so it is never necessary to declare something as an auto auto auto auto.What is the difference between char a[] = ―string‖; and char *p = ―string‖; ?Answer1a[] = ―string‖;char *p = ―string‖;The difference is this:p is pointing to a constant string, you can never safely sayp[3]=‘x‘;however you can always say a[3]=‘x‘;char a[]=‖string‖; - character array initialization.char *p=‖string‖ ; - non-const pointer to a const-string.( this is permitted only in the case of char pointer in C++ to preserve backward compatibility with C.)Answer2a[] = ―string‖;char *p = ―string‖;a[] will have 7 bytes. However, p is only 4 bytes. P is pointing to an adress is either BSS or the data section (depending on which compiler — GNU for the former and CC for the latter). Answer3char a[] = ―string‖;char *p = ―string‖;for char a[]…….using the array notation 7 bytes of storage in the static memory block are taken up, one for each character and one for the terminating nul character.But, in the pointer notation char *p………….the same 7 by tes required, plus N bytes to store the pointer variable ―p‖ (where N depends on the system but is usually a minimum of 2 bytes and can be 4 or more)……How do I declare an array of N pointers to functions returning pointers to functions returning pointers to characters?Answer1If you want the code to be even slightly readable, you will use typedefs.typedef char* (*functiontype_one)(void);typedef functiontype_one (*functiontype_two)(void);functiontype_two myarray[N]; //assuming N is a const integralAnswer2char* (* (*a[N])())()Here a is that array. And according to question no function will not take any parameter value. What does extern mean in a function declaration?It tells the compiler that a variable or a function exists, even if the compiler hasn‘t yet seen it in the file currently being compiled. This variable or function may be defined in another file or further down in the current file.How do I initialize a pointer to a function?This is the way to initialize a pointer to a functionvoid fun(int a){}void main(){void (*fp)(int);fp=fun;fp(1);}How do you link a C++ program to C functions?By using the extern ―C‖ linkage specification around the C function declarations.Explain the scope resolution operator.It permits a program to reference an identifier in the global scope that has been hidden by another identifier with the same name in the local scope.What are the differences between a C++ struct and C++ class?The default member and base-class access specifiers are different.How many ways are there to initialize an int with a constant?Two.There are two formats for initializers in C++ as shown in the example that follows. The first format uses the traditional C notation. The second format uses constructor notation.int foo = 123;int bar (123);How does throwing and catching exceptions differ from using setjmp and longjmp?The throw operation calls the destructors for automatic objects instantiated since entry to the try block.What is a default constructor?Default constructor WITH arguments class B { public: B (int m = 0) : n (m) {} int n; }; int main(int argc, char *argv[]) { B b; return 0; }What is a conversion constructor?A constructor that accepts one argument of a different type.What is the difference between a copy constructor and an overloaded assignment operator?A copy constructor constructs a new object by using the content of the argument object. An overloaded assignment operator assigns the contents of an existing object to another existing object of the same class.When should you use multiple inheritance?There are three acceptable answers: ―Never,‖ ―Rarely,‖ and ―When the problem domain cannot be accurately modeled any other way.‖Explain the ISA and HASA class relationships. How would you implement each in a class design?。

C++ 常见英文面试笔试题

C/C++ Programming interview questions and answersBy Satish Shetty, July 14th, 2004What is encapsulation??Containing and hiding information about an object, such as internal data structures and code. Encapsulation isolates the internal complexity of an object's operation from the rest of the application. For example, a client component asking for net revenue from a business object need not know the data's origin.What is inheritance?Inheritance allows one class to reuse the state and behavior of another class. The derived class inherits the properties and method implementations of the base class and extends it by overriding methods and adding additional properties and methods.What is Polymorphism??Polymorphism allows a client to treat different objects in the same way even if they were created from different classes and exhibit different behaviors.Y ou can use implementation inheritance to achieve polymorphism in languages such as C++ and Java.Base class object's pointer can invoke methods in derived class objects.Y ou can also achieve polymorphism in C++ by function overloading and operator overloading.What is constructor or ctor?Constructor creates an object and initializes it. It also creates vtable for virtual functions. It is different from other methods in a class.What is destructor?Destructor usually deletes any extra resources allocated by the object.What is default constructor?Constructor with no arguments or all the arguments has default values.What is copy constructor?Constructor which initializes the it's object member variables ( by shallow copying) with another object of the same class. If you don't implement one in your class then compiler implements one for you.for example:Boo Obj1(10); // calling Boo constructorBoo Obj2(Obj1); // calling boo copy constructorBoo Obj2 = Obj1;// calling boo copy constructorWhen are copy constructors called?Copy constructors are called in following cases:a) when a function returns an object of that class by valueb) when the object of that class is passed by value as an argument to a functionc) when you construct an object based on another object of the same classd) When compiler generates a temporary objectWhat is assignment operator?Default assignment operator handles assigning one object to another of the same class. Member to member copy (shallow copy)What are all the implicit member functions of the class? Or what are all the functions which compiler implements for us if we don't define one.??default ctorcopy ctorassignment operatordefault destructoraddress operatorWhat is conversion constructor?constructor with a single argument makes that constructor as conversion ctor and it can be used for type conversion.for example:class Boo{public:Boo( int i );};Boo BooObject = 10 ; // assigning int 10 Boo objectWhat is conversion operator??class can have a public method for specific data type conversions.for example:class Boo{double value;public:Boo(int i )operator double(){return value;}};Boo BooObject;double i = BooObject; // assigning object to variable i of type double. now conversion operator gets called to assign the value.What is diff between malloc()/free() and new/delete?malloc allocates memory for object in heap but doesn't invoke object's constructor to initiallize the object.new allocates memory and also invokes constructor to initialize the object.malloc() and free() do not support object semanticsDoes not construct and destruct objectsstring * ptr = (string *)(malloc (sizeof(string)))Are not safeDoes not calculate the size of the objects that it constructReturns a pointer to voidint *p = (int *) (malloc(sizeof(int)));int *p = new int;Are not extensiblenew and delete can be overloaded in a class"delete" first calls the object's termination routine (i.e. its destructor) and then releases the space the object occupied on the heap memory. If an array of objects was created using new, then delete must be told that it is dealing with an array by preceding the name with an empty []:-Int_t *my_ints = new Int_t[10];...delete []my_ints;what is the diff between "new" and "operator new" ?"operator new" works like malloc.What is difference between template and macro??There is no way for the compiler to verify that the macro parameters are of compatible types. The macro is expanded without any special type checking.If macro parameter has a postincremented variable ( like c++ ), the increment is performed two times.Because macros are expanded by the preprocessor, compiler error messages will refer to the expanded macro, rather than the macro definition itself. Also, the macro will show up in expanded form during debugging.Macro:#define min(i, j) (i < j ? i : j)template:template<class T>T min (T i, T j){return i < j ? i : j;}What are C++ storage classes?autoregisterstaticexternauto: the default. V ariables are automatically created and initialized when they are defined and are destroyed at the end of the block containing their definition. They are not visible outside that blockregister: a type of auto variable. a suggestion to the compiler to use a CPU register for performancestatic:a variable that is known only in the function that contains its definition but is never destroyed and retains its value between calls to that function. It exists from the time the program begins executionextern: a static variable whose definition and placement is determined when all object and library modules are combined (linked) to form the executable code file. It can be visible outside the file where it is defined.What are storage qualifiers in C++ ?They are..constvolatilemutableConst keyword indicates that memory once initialized, should not be altered by a program. volatile keyword indicates that the value in the memory location can be altered even though nothing in the programcode modifies the contents. for example if you have a pointer to hardware location that contains the time, where hardware changes the value of this pointer variable and not the program. The intent of this keyword to improve the optimization ability of the compiler.mutable keyword indicates that particular member of a structure or class can be altered even if a particular structure variable, class, or class member function is constant.{char name[80];mutable double salary;}const data MyStruct = { "Satish Shetty", 1000 }; //initlized by complierstrcpy ( , "Shilpa Shetty"); // compiler errorMyStruct.salaray = 2000 ; // complier is happy allowedWhat is reference ??reference is a name that acts as an alias, or alternative name, for a previously defined variable or an object.prepending variable with "&" symbol makes it as reference.for example:int a;int &b = a;What is passing by reference?Method of passing arguments to a function which takes parameter of type reference.for example:void swap( int & x, int & y ){int temp = x;x = y;y = temp;}int a=2, b=3;swap( a, b );Basically, inside the function there won't be any copy of the arguments "x" and "y" instead they refer to original variables a and b. so no extra memory needed to pass arguments and it is more efficient.When do use "const" reference arguments in function?a) Using const protects you against programming errors that inadvertently alter data.b) Using const allows function to process both const and non-const actual arguments, while a function without const in the prototype can only accept non constant arguments.c) Using a const reference allows the function to generate and use a temporary variable appropriately.When are temporary variables created by C++ compiler?Provided that function parameter is a "const reference", compiler generates temporary variable in following 2 ways.a) The actual argument is the correct type, but it isn't Lvaluedouble Cube(const double & num){num = num * num * num;return num;}double temp = 2.0;double value = cube(3.0 + temp); // argument is a expression and not a Lvalue;b) The actual argument is of the wrong type, but of a type that can be converted to the correct type long temp = 3L;double value = cuberoot ( temp); // long to double conversionWhat is virtual function?When derived class overrides the base class method by redefining the same function, then if client wants to access redefined the method from derived class through a pointer from base class object, then you must define this function in base class as virtual function.class parent{void Show(){cout << "i'm parent" << endl;}};class child: public parent{void Show(){cout << "i'm child" << endl;}};parent * parent_object_ptr = new child;parent_object_ptr->show() // calls parent->show() inow we goto virtual world...class parent{virtual void Show(){cout << "i'm parent" << endl;}};class child: public parent{void Show(){cout << "i'm child" << endl;}};parent * parent_object_ptr = new child;parent_object_ptr->show() // calls child->show()What is pure virtual function? or what is abstract class?When you define only function prototype in a base class without implementation and do the complete implementation in derived class. This base class is called abstract class and client won't able to instantiate an object using this base class.Y ou can make a pure virtual function or abstract class this way..class Boo{void foo() = 0;}Boo MyBoo; // compilation errorWhat is Memory alignment??The term alignment primarily means the tendency of an address pointer value to be a multiple of some power of two. So a pointer with two byte alignment has a zero in the least significant bit. And a pointer with four byte alignment has a zero in both the two least significant bits. And so on. More alignment means a longer sequence of zero bits in the lowest bits of a pointer.What problem does the namespace feature solve?Multiple providers of libraries might use common global identifiers causing a name collision when an application tries to link with two or more such libraries. The namespace feature surrounds a library's external declarations with a unique namespace that eliminates the potential for those collisions.namespace [identifier] { namespace-body }A namespace declaration identifies and assigns a name to a declarative region.The identifier in a namespace declaration must be unique in the declarative region in which it is used. The identifier is the name of the namespace and is used to reference its members.What is the use of 'using' declaration?A using declaration makes it possible to use a name from a namespace without the scope operator.What is an Iterator class?A class that is used to traverse through the objects maintained by a container class. There are five categories of iterators: input iterators, output iterators, forward iterators, bidirectional iterators, random access. An iterator is an entity that gives access to the contents of a container object without violating encapsulation constraints. Access to the contents is granted on a one-at-a-time basis in order. The order can be storage order (as in lists and queues) or some arbitrary order (as in array indices) or according to some ordering relation (as in an ordered binary tree). The iterator is a construct, which provides an interface that, when called, yields either the next element in the container, or some value denoting the fact that there are no more elements to examine. Iterators hide the details of access to and update of the elements of a container class. Something like a pointer.What is a dangling pointer?A dangling pointer arises when you use the address of an object after its lifetime is over. This may occur in situations like returning addresses of the automatic variables from a function or using the address of the memory block after it is freed.What do you mean by Stack unwinding?It is a process during exception handling when the destructor is called for all local objects in the stack between the place where the exception was thrown and where it is caught.Name the operators that cannot be overloaded??sizeof, ., .*, .->, ::, ?:What is a container class? What are the types of container classes?A container class is a class that is used to hold objects in memory or external storage. A container class acts as a generic holder. A container class has a predefined behavior and a well-known interface. A container class is a supporting class whose purpose is to hide the topology used for maintaining the list of objects in memory. When a container class contains a group of mixed objects, the container is called a heterogeneous container; when the container is holding a group of objects that are all the same, the container is called a homogeneous container.What is inline function??The __inline keyword tells the compiler to substitute the code within the function definition for every instance of a function call. However, substitution occurs only at the compiler's discretion. For example, the compiler does not inline a function if its address is taken or if it is too large to inline.What is overloading??With the C++ language, you can overload functions and operators. Overloading is the practice of supplying more than one definition for a given function name in the same scope.- Any two functions in a set of overloaded functions must have different argument lists.- Overloading functions with argument lists of the same types, based on return type alone, is an error.What is Overriding?To override a method, a subclass of the class that originally declared the method must declare a method with the same name, return type (or a subclass of that return type), and same parameter list. The definition of the method overriding is:· Must have same method name.· Must have same data type.· Must have same argument list.Overriding a method means that replacing a method functionality in child class. To imply overriding functionality we need parent and child classes. In the child class you define the same method signature as one defined in the parent class.What is "this" pointer?The this pointer is a pointer accessible only within the member functions of a class, struct, or union type. It points to the object for which the member function is called. Static member functions do not have a this pointer.When a nonstatic member function is called for an object, the address of the object is passed as a hidden argument to the function. For example, the following function callmyDate.setMonth( 3 );can be interpreted this way:setMonth( &myDate, 3 );The object's address is available from within the member function as the this pointer. It is legal, though unnecessary, to use the this pointer when referring to members of the class.What happens when you make call "delete this;" ??The code has two built-in pitfalls. First, if it executes in a member function for an extern, static, or automatic object, the program will probably crash as soon as the delete statement executes. There is no portable way for an object to tell that it was instantiated on the heap, so the class cannot assert that its object is properly instantiated. Second, when an object commits suicide this way, theusing program might not know about its demise. As far as the instantiating program is concerned, the object remains in scope and continues to exist even though the object did itself in. Subsequent dereferencing of the pointer can and usually does lead to disaster.Y ou should never do this. Since compiler does not know whether the object was allocated on the stack or on the heap, "delete this" could cause a disaster.How virtual functions are implemented C++?Virtual functions are implemented using a table of function pointers, called the vtable. There is one entry in the table per virtual function in the class. This table is created by the constructor of the class. When a derived class is constructed, its base class is constructed first which creates the vtable. If the derived class overrides any of the base classes virtual functions, those entries in the vtable are overwritten by the derived class constructor. This is why you should never call virtual functions from a constructor: because the vtable entries for the object may not have been set up by the derived class constructor yet, so you might end up calling base class implementations of those virtual functionsWhat is name mangling in C++??The process of encoding the parameter types with the function/method name into a unique name is called name mangling. The inverse process is called demangling.For example Foo::bar(int, long) const is mangled as `bar__C3Fooil'.For a constructor, the method name is left out. That is Foo::Foo(int, long) const is mangled as `__C3Fooil'.What is the difference between a pointer and a reference?A reference must always refer to some object and, therefore, must always be initialized; pointers do not have such restrictions. A pointer can be reassigned to point to different objects while a reference always refers to an object with which it was initialized.How are prefix and postfix versions of operator++() differentiated?The postfix version of operator++() has a dummy parameter of type int. The prefix version does not have dummy parameter.What is the difference between const char *myPointer and char *const myPointer?Const char *myPointer is a non constant pointer to constant data; while char *const myPointer is a constant pointer to non constant data.How can I handle a constructor that fails?throw an exception. Constructors don't have a return type, so it's not possible to use return codes. The best way to signal constructor failure is therefore to throw an exception.How can I handle a destructor that fails?Write a message to a log-file. But do not throw an exception.The C++ rule is that you must never throw an exception from a destructor that is being called during the "stack unwinding" process of another exception. For example, if someone says throw Foo(), the stack will be unwound so all the stack frames between the throw Foo() and the } catch (Foo e) { will get popped. This is called stack unwinding.During stack unwinding, all the local objects in all those stack frames are destructed. If one ofthose destructors throws an exception (say it throws a Bar object), the C++ runtime system is in a no-win situation: should it ignore the Bar and end up in the } catch (Foo e) { where it was originally headed? Should it ignore the Foo and look for a } catch (Bar e) { handler? There is no good answer -- either choice loses information.So the C++ language guarantees that it will call terminate() at this point, and terminate() kills the process. Bang you're dead.What is Virtual Destructor?Using virtual destructors, you can destroy objects without knowing their type - the correct destructor for the object is invoked using the virtual function mechanism. Note that destructors can also be declared as pure virtual functions for abstract classes.if someone will derive from your class, and if someone will say "new Derived", where "Derived" is derived from your class, and if someone will say delete p, where the actual object's type is "Derived" but the pointer p's type is your class.Can you think of a situation where your program would crash without reaching the breakpoint which you set at the beginning of main()?C++ allows for dynamic initialization of global variables before main() is invoked. It is possible that initialization of global will invoke some function. If this function crashes the crash will occur before main() is entered.Name two cases where you MUST use initialization list as opposed to assignment in constructors.Both non-static const data members and reference data members cannot be assigned values; instead, you should use initialization list to initialize them.Can you overload a function based only on whether a parameter is a value or a reference?No. Passing by value and by reference looks identical to the caller.What are the differences between a C++ struct and C++ class?The default member and base class access specifiers are different.The C++ struct has all the features of the class. The only differences are that a struct defaults to public member access and public base class inheritance, and a class defaults to the private access specifier and private base class inheritance.What does extern "C" int func(int *, Foo) accomplish?It will turn off "name mangling" for func so that one can link to code compiled by a C compiler.How do you access the static member of a class?<ClassName>::<StaticMemberName>What is multiple inheritance(virtual inheritance)? What are its advantages and disadvantages?Multiple Inheritance is the process whereby a child can be derived from more than one parent class. The advantage of multiple inheritance is that it allows a class to inherit the functionality of more than one base class thus allowing for modeling of complex relationships. The disadvantage of multiple inheritance is that it can lead to a lot of confusion(ambiguity) when two base classes implement a method with the same name.What are the access privileges in C++? What is the default access level?The access privileges in C++ are private, public and protected. The default access level assigned to members of a class is private. Private members of a class are accessible only within the class and by friends of the class. Protected members are accessible by the class itself and it's sub-classes. Public members of a class can be accessed by anyone.What is a nested class? Why can it be useful?A nested class is a class enclosed within the scope of another class. For example:// Example 1: Nested class//class OuterClass{class NestedClass{// ...};// ...};Nested classes are useful for organizing code and controlling access and dependencies. Nested classes obey access rules just like other parts of a class do; so, in Example 1, if NestedClass is public then any code can name it as OuterClass::NestedClass. Often nested classes contain private implementation details, and are therefore made private; in Example 1, if NestedClass is private, then only OuterClass's members and friends can use NestedClass.When you instantiate as outer class, it won't instantiate inside class.What is a local class? Why can it be useful?local class is a class defined within the scope of a function -- any function, whether a member function or a free function. For example:// Example 2: Local class//int f(){class LocalClass{// ...};// ...};Like nested classes, local classes can be a useful tool for managing code dependencies.Can a copy constructor accept an object of the same class as parameter, instead of reference of the object?No. It is specified in the definition of the copy constructor itself. It should generate an error if a programmer specifies a copy constructor with a first argument that is an object and not a reference.。

c 面试题及答案

c 面试题及答案提示：根据题目的要求，我将为你提供一份面试题及答案的文章。

请注意，由于题目只提供了一个字母"c"，所以无法得知具体的面试题内容，请自行替换为实际的面试题。

以下是一份示例，根据实际情况可以根据需要进行修改。

----------------------------------面试题及答案一、面试题面试题：请描述一下你过去的工作经验。

二、答案在过去的工作经验中，我曾经担任过多个职位，积累了丰富的专业知识与实践经验，以下是我过去的主要工作经历：首先，我曾在一家知名IT公司担任软件工程师一职，参与了多个软件开发项目。

通过这些项目，我学习到了如何与团队成员进行有效的合作，并在高压下保持良好的工作状态。

在这个公司，我也学会了如何与客户进行沟通，理解他们的需求，并提供满足他们需求的解决方案。

其次，我曾在一家跨国企业担任项目经理一职。

在这个职位上，我负责领导一个团队完成一个复杂的产品开发项目。

我学会了如何有效地组织和分配团队资源，确保项目按时交付，并达到客户的期望。

在项目中，我积累了很多关于项目管理和团队管理方面的经验。

另外，我也曾在一家初创公司担任市场营销经理一职。

在这个职位上，我负责制定市场推广策略，并将其转化为实际的营销活动。

我通过市场调研和数据分析，了解了如何确定目标客户，并制定精确的推广方案。

在这个过程中，我也学会了如何与不同的利益相关者进行有效的沟通，并建立了稳定的合作关系。

总结来说，我的过去工作经验让我学到了很多宝贵的东西。

这些经验让我成为一位具备综合能力和沟通能力的候选人。

我相信这些经验将帮助我在未来的工作岗位上取得成功。

三、结论通过以上对我过去工作经验的描述，我希望能够展示出自己在职业生涯中所取得的成就和经验。

我相信这些经验将为我在未来的工作中提供宝贵的参考和指导，并促使我不断成长和进步。

谢谢您的关注。

C和C 笔试、面试题目(2)

C/C++ 笔试、面试题目(2) 20. Ado与的相同与不同？除了“能够让应用程序处理存储于DBMS 中的数据“这一基本相似点外，两者没有太多共同之处。

但是Ado使用OLE DB 接口并基于微软的COM 技术，而拥有自己的接口并且基于微软的.NET 体系架构。

众所周知.NET 体系不同于COM 体系，接口也就完全不同于ADO和OLE DB 接口，这也就是说和ADO是两种数据访问方式。

提供对XML 的支持。

21. New delete 与malloc free 的联系与区别? 答案：都是在堆(heap)上进行动态的内存操作。

用malloc函数需要指定内存分配的字节数并且不能初始化对象，new 会自动调用对象的构造函数。

delete 会调用对象的destructor，而free 不会调用对象的destructor.22. #define DOUBLE(x) x+x ，i = 5*DOUBLE(5)； i 是多少？答案：i 为30。

23. 有哪几种情况只能用intialization list 而不能用assignment? 答案：当类中含有const、reference 成员变量；基类的构造函数都需要初始化表。

24. C++是不是类型安全的？答案：不是。

两个不同类型的指针之间可以强制转换（用reinterpret cast)。

C#是类型安全的。

25. main 函数执行以前，还会执行什么代码？答案：全局对象的构造函数会在main 函数之前执行。

26. 描述内存分配方式以及它们的区别? 1）从静态存储区域分配。

内存在程序编译的时候就已经分配好，这块内存在程序的整个运行期间都存在。

例如全局变量，static 变量。

2）在栈上创建。

在执行函数时，函数内局部变量的存储单元都可以在栈上创建，函数执行结束时这些存储单元自动被释放。

栈内存分配运算内置于处理器的指令集。

3）从堆上分配，亦称动态内存分配。

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