Input and Output

Input : In any programming language input means to feed some data into program. This can be given in the form of file or from command line. C programming language provides a set of built-in functions to read given input and feed it to the program as per requirement.

Output : In any programming language output means to display some data on screen, printer or in any file. C programming language provides a set of built-in functions to output required data.

printf() function
This is one of the most frequently used functions in C for output. ( we will discuss what is function in subsequent chapter. ).

Try following program to understand printf() function.

#include main() { int dec = 5; char str[] = "abc"; char ch = 's'; float pi = 3.14; printf("%d %s %f %c\n", dec, str, pi, ch); }

The output of the above would be:

5 abc 3.140000 c

Here %d is being used to print an integer, %s is being usedto print a string, %f is being used to print a float and %c is being used to print a character.

scanf() function
This is the function which can be used to to read an input from the command line.

Try following program to understand scanf() function.

#include main() { int x; int args; printf("Enter an integer: "); if (( args = scanf("%d", &x)) == 0) { printf("Error: not an integer\n"); } else { printf("Read in %d\n", x); } }

Here %d is being used to read an integer value and we are passing &x to store the vale read input. Here &indicates the address of variable x.

This program will prompt you to enter a value. Whatever value you will enter at command prompt that will be output at the screen using printf() function. If you enter a non-integer value then it will display an error message.

Enter an integer: 20 Read in 20