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Programming languages - C Programming

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Lesson Description


Lession - #21 C Input and Output


When we say Input, it means to feed some data into a program. An input can be given in the form of a file or from the command line. C programming provides a set of built-in functions to read the given input and feed it to the program as per requirement.
When we say Output, it means to display some data on screen, printer, or in any file. C programming provides a set of built-in functions to output the data on the computer screen as well as to save it in text or binary files.

The Standard Files

C programming treats all the devices as files. So devices such as the display are addressed in the same way as files and the following three files are automatically opened when a program executes to provide access to the keyboard and screen.
Standard File File Pointer Device
Standard input stdin Keyboard
Standard output stdout Screen
Standard error stderr Your screen
The file pointers are the means to access the file for reading and writing purpose. This section explains how to read values from the screen and how to print the result on the screen.
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; }
When the above code is compiled and executed, it waits for you to input some text. When you enter a text and press enter, then the program proceeds and reads only a single character and displays it as follows −
 
$./a.out
Enter a value : this is test
You entered: t