programming in ANSI C-Chapter 4 Managing input and output operations

e.g. scanf("%d%d%f", &n1, &n2, &f); Form: input: scanf ("control string", arg1, …, argn); 12 345↵ 67.89↵ e.g. scanf("%d,%c", &num, &ch); result: 12⇒n1, 345⇒n2, 67.89 ⇒f
e.g. scanf("a=%d, b=%d", &a, scanf("%d, %d", &a, &b); &b); Form: input: scanf ("control b=345↵ arg1, …, argn); a=12, string", 12, 345↵ result: 12⇒a, 345⇒b e.g. scanf("%d,%c", &num, &ch);
1 %d, %i Signed decimal integer 2 %x, %X Unsigned hexadecimal integer (without leading 0x) 3 %o Unsigned octal integer (without leading 0) 4 %u Unsigned decimal integer 5 %c Single character 6 %s Sting 7 %f Real number in decimal notation 8 %e, %E Real number in exponential notation Real number either f-type or e-type depending on 9 %g, %G the length of the value without insignificant zero 10 %% %
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printf( ) – Formatted Output
Accessorial format specifications
1 w Specifies the minimum field width for the output. To real number, specifies the number of digits after the decimal point (rounded). To string, instructs the first p characters to be outputted. To integer or single character, it is invalid. Precede d, i, o, x, u to outputs long type integer. Precede f, e, g to outputs double type real number. Left-justified, and remaining field will be blank.
h l w * Precede d, i, o, u, x to read short type integer. Precede d, i, o, x, u to read long type integer. Precede f, e, g to read double type real number. Specify the field width of the data to be read. Specify the input field to be skipped.
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scanf( ) – Formatted Input
Form: e.g.
1.
scanf ("control string", arg1, …, argn); scanf("%d,%c", &num, &ch);
format specifications %d, %i, %o, %x, %u, %c, %s, %f, %e, %g the same as those in printf function.
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scanf( ) – Formatted Input
Form: e.g. scanf ("control string", arg1, …, argn); scanf("%d%c", &i, &ch); input: 12 a↵ e.g. scanf("%d,%c", &num, &ch); result: 12⇒i, ' ' ⇒ch Separators
3.
input: Separators result:
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12, 345↵ 12 345↵ 12⇒a, nothing⇒b nothing⇒a, nothing⇒b
It also can specify separators, that is those characters except format specifications. In this way, the input must accord with the specified format, otherwise the input most probably is read in by errors.
Escape sequence characters. Format specifications.
e.g. %f, %d
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printf( ) – Formatted Output
Form: printf("control string", arg1, …, argn);
e.g. printf("price=$%.2f\n, amount=%d.", pr*am, am);
printf( ) putchar( )
standard input and output
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getchar( ) & putchar( )
Form: #include <stdio.h> variable = getchar(); main() putchar(character); { char c ; c = getchar ( ); putchar ( c ); putchar ( getchar () ); printf ( "%c", getchar () ); putchar ('D'); } printf("%d", getchar()); }
2.
printf("%c, %d", 97, 'a'); The outputted expression list: (arg1, …, argn) Output: a, 97 There can be no any expression or more than one expression. They are separated by comma. printf("%d, %u", 32767+1, 32767+1); Output: -32768, 32768 In spite of what type these expressions are, they are always outputted in specified format.
③
3.
When it read in a character, the blank space, tab and newline character are no longer separators, but as a valid character.
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scanf( ) – Formatted Input
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scanf( ) – Formatted Input
e.g.
scanf("%d%*d%d", &a, &b); input: 12 345 67↵ Form: scanf ("control string", arg1, …, argn); result: 12⇒a, 67⇒b e.g. scanf("%d,%c", &num, &ch); &i, &f); scanf("%3d%f", &i, &f); scanf("%3d%*2d%f", e.g. input: 12345.6789↵ 123456.789↵ 2. Accessorial format 123⇒i, 45.6789⇒f specifications result: 6.789⇒f
Chapter 4 Managing Input and Output Operations
PROGRAMMING IN ANSI C
3/5/2011
Chapter 4
C hasn’t any built-in input/output statements as part of its syntax. All of input/output operations are carried out through standard input/output functions. scanf( ) getchar( ) gets( ) puts( ) e.g. printf( ) # include <stdio.h> # include "stdio.h"
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