C programming examples

c program examples

Example 1 - C hello world program
/* A very simple c program printing a string on screen*/

#include <stdio.h>
 
main()
{
    printf("Hello World\n");
    return 0;
}

Output of above program:
"Hello World"

Example 2 - c program to take input from user using scanf

#include <stdio.h>
 
main()
{
   int number;
 
   printf("Enter an integer\n");
   scanf("%d",&number);
 
   printf("Integer entered by you is %d\n", number);
 
   return 0;
}

Output:
Enter a number
5
Number entered by you is 5

Example 3 - using if else control instructions

#include <stdio.h>
 
main()
{
   int x = 1;
 
   if ( x == 1 )
      printf("x is equal to one.\n");
   else
      printf("For comparison use == as = is the assignment operator.\n");
 
   return 0;
}

Output:
x is equal to one.

Example 4 - loop example

#include <stdio.h>
 
main()
{
   int value = 1;
 
   while(value<=3)
   {
      printf("Value is %d\n", value);
      value++;
   }
 
   return 0;
}

Output:
Value is 1
Value is 2
Value is 3

Example 5 - c program for prime number

#include <stdio.h>
 
main()
{
   int n, c;
 
   printf("Enter a number\n");
   scanf("%d", &n);
 
   if ( n == 2 )
      printf("Prime number.\n");
   else
   {
       for ( c = 2 ; c <= n - 1 ; c++ )
       {
           if ( n % c == 0 )
              break;
       }
       if ( c != n )
          printf("Not prime.\n");
       else
          printf("Prime number.\n");
   }
   return 0;
}

Example 6 - command line arguments

#include <stdio.h>
 
main(int argc, char *argv[])
{
   int c;
 
   printf("Number of command line arguments passed: %d\n", argc);
 
   for ( c = 0 ; c < argc ; c++)
      printf("%d. Command line argument passed is %s\n", c+1, argv[c]);
 
   return 0;
}

Above c program prints the number and all arguments which are passed to it.

Example 7 - Array program

#include <stdio.h>
 
main() 
{
    int array[100], n, c;
 
    printf("Enter the number of elements in array\n");
    scanf("%d", &n);
 
    printf("Enter %d elements\n", n);
 
    for ( c = 0 ; c < n ; c++ ) 
        scanf("%d", &array[c]);
 
    printf("Array elements entered by you are:\n");
 
    for ( c = 0 ; c < n ; c++ ) 
        printf("array[%d] = %d\n", c, array[c]);
 
    return 0;
}

Example 8 - function program

#include <stdio.h>
 
void my_function();
 
main()
{
   printf("Main function.\n");
 
   my_function();
 
   printf("Back in function main.\n");
 
   return 0;
}
 
void my_function()
{
   printf("Welcome to my function. Feel at home.\n");
}

Example 9 - Using comments in a program

#include <stdio.h>
 
main()
{
   // Single line comment in c source code
 
   printf("Writing comments is very useful.\n");
 
   /*
    * Multi line comment syntax
    * Comments help us to understand code later easily.
    * Will you write comments while developing programs ?
    */
 
   printf("Good luck c programmer.\n"); 
 
   return 0;
}

Example 10 - using structures in c programming

#include <stdio.h>
 
struct programming
{
    float constant;
    char *pointer;
};
 
main()
{
   struct programming variable;
   char string[] = "Programming in Software Development.";   
 
   variable.constant = 1.23;
   variable.pointer = string;
 
   printf("%f\n", variable.constant);
   printf("%s\n", variable.pointer);
 
   return 0;
}

Example 11 - c program for Fibonacci series

#include <stdio.h>
 
main()
{
   int n, first = 0, second = 1, next, c;
 
   printf("Enter the number of terms\n");
   scanf("%d",&n);
 
   printf("First %d terms of Fibonacci series are :-\n",n);
 
   for ( c = 0 ; c < n ; c++ )
   {
      if ( c <= 1 )
         next = c;
      else
      {
         next = first + second;
         first = second;
         second = next;
      }
      printf("%d\n",next);
   }
 
   return 0;
}

Example 12 - c graphics programming

#include <graphics.h>
#include <conio.h>
 
main()
{
    int gd = DETECT, gm;
 
    initgraph(&gd, &gm,"C:\\TC\\BGI");
 
    outtextxy(10,20, "Graphics source code example.");
 
    circle(200, 200, 50);
 
    setcolor(BLUE);
 
    line(350, 250, 450, 50);
 
    getch();
    closegraph( );
    return 0;
}

For GCC users

If you are using GCC on Linux operating system then you need to modify programs. For example consider the following program which prints first ten natural numbers

#include <stdio.h>
#include <conio.h>
 
int main()
{
    int c;
 
    for ( c = 1 ; c <= 10 ; c++ )
        printf("%d\n", c);
 
    getch();
    return 0;
}

Above source code includes a header file <conio.h> and uses function getch, but this file is Borland specific so it works in turbo c compiler but not in GCC. So the code for GCC should be like

#include <stdio.h>
 
int main()
{
    int c;
 
    /* for loop */
 
    for ( c = 1 ; c <= 10 ; c++ )
        printf("%d\n", c);
 
    return 0;
}