C provides several functions that give different levels of input and output capability.
The input and output functions in C are built around the concept of a set
of standard data streams. These standard data streams or files are opened by
the operating system and are available to every C and assembler program for use
without having to open or close the files.
The input/output functions are of two kinds:
nonformatted and formatted functions.
UNFORMATTED
INPUT AND OUTPUT FUNCTIONS
Non-formatted input and output can be carried out by standard
input-output library functions in C. For input/output functions, it
reads/prints a single character from/on the console.
The
getchar() and putchar() Functions
The int getchar(void) function reads the next available
character from the screen and returns it as an integer. This function reads
only single character at a time. You can use this method in the loop in case
you want to read more than one character from the screen.
The int putchar(int c) function puts the passed
character on the screen and returns the same character. This function puts only
single character at a time. You can use this method in the loop in case you
want to display more than one character on the screen.
Check the following example −
#include <stdio.h>
int main( ) {
int
c;
printf( "Enter a value
:");
c = getchar( );
printf( "\nYou entered:
");
putchar( c );
return 0;
}
The gets()
and puts() Functions
The char gets(char *s) function reads a line from stdin into
the buffer pointed to by s until either a terminating newline
or EOF (End of File).
The int puts(const char *s) function writes the string
's' and 'a' trailing newline to stdout.
#include <stdio.h>
int main( ) {
char str[100];
printf( "Enter a value :");
gets( str );
printf( "\nYou entered:
");
puts( str );
return 0;
}
FORMATTED
INPUT AND OUTPUT FUNCTIONS
If input and output is required in a specified format the standard
library functions scanf() and printf() are used.
The scanf()
and printf() Functions
•
The general form of printf()
function is
printf(“control_string”,variable1,variable2,...);
The control string is important because it specifies the type of each
variable in the list and how the user wants it printed.
The control string is also called the format string.
The format string in printf(),
enclosed in quotation marks, has three types of objects:
Ordinary
characters: these are copied to output
Conversion
specifier field: denoted by %
containing the codes and by optional modifiers such as width, precision, flag, and size
Control
code: optional control characters such as \n,\b, and \t
The format string in printf()
has the following general form:
Printf(“<control code><character string><%conversion
specifier> <control code>”);
•
The general form of
scanf function is
scanf(“control_string”,variable1_address, variable2_address,...);
The scanf() function should have the addresses of the variables rather
than just their values. This means that simple variables have to be passed with
a proceeding &.
scanf(“%d%d%d%c”, &a, &b, &c,
&x);
Ex:
#include <stdio.h>
int main( ) {
char str[100];
int i;
printf( "Enter a value
:");
scanf("%s %d", str,
&i);
printf( "\nYou entered: %s
%d ", str, i);
return 0;
}
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