In this article, I have provided samples of a simple C program with their code and output, which can be useful for C language beginners.

So, before we begin, I assume you have basic knowledge of C language code like declaring variables, using functions like printf() and scanf(), if not, you need to carefully understand and code for first three examples, and then proceed for other simple C programming examples with output.

Hello World program in C

Let's get started with the easier and simplest program in C to print "Hello world"

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

Output;

Hello World

Get user input using scanf and print it in C

    #include <stdio.h>    
    void main()
    {
      int num;
     
      printf("Enter a number\n");
      scanf("%d", &num); // %d is used for an integer
     
      printf("The number is: %d\n", num);
     
    }

Output:

Enter a number
5
The number is: 5

Addition program in C ( Adding two integers)

I have just recently added the article, related to this in which I have explained about adding two integers in C, but I will again write the code here for you

#include <stdio.h>
void main()
{
    //declare three variables, for firstNumber+secondNumber=TotalSumOfBoth
    int firstNumber, secondNumber, TotalSumOfBoth;
    
    //ask the user to get first number to add
    printf("Enter first number: ");

    //store it in first variable using scanf() function
    scanf("%d", &firstNumber);
    
    //ask the user to get second number to add
    printf("Enter second number:");

    //store it in second variable using scanf() function
    scanf("%d", &secondNumber);

    // sum of two numbers in stored in variable TotalSumOfBoth
    TotalSumOfBoth = firstNumber + secondNumber;

    // Displays sum      
    printf("%d + %d = %d", firstNumber, secondNumber, TotalSumOfBoth);

}

Output:

Enter first number: 10
Enter second number:20
10 + 20 = 30

C program to find the maximum number between three numbers

To find the maximum between 3 numbers, we need to follow these steps:

  1. Take three integer variables, say A, B & C
  2. Ask the user to enter three numbers and save them in above-declared variables
  3. If A is greater than B & C, Display A is the largest value
  4. If B is greater than A & C, Display B is the largest value
  5. If C is greater than A & B, Display A is the largest value
  6. Otherwise, Display A, B & C are not unique values

Now, we have the steps, let's implement it in C Code

#include <stdio.h>

int main() {
   int a, b, c;

    /* Input three numbers from user */
    printf("Enter three numbers: ");
    scanf("%d%d%d", &a, &b, &c);

   if ( a > b && a > c )
      printf("%d is the largest.", a);
   else if ( b > a && b > c )
      printf("%d is the largest.", b);
   else if ( c > a && c > b )
      printf("%d is the largest.", c);
   else   
      printf("Values are not unique");

   return 0;
}

Output:

Enter three numbers: 10
30
18
30 is the largest.

c-programming-examples-with-output-min.png

Find number is even or odd program in C

Here the steps, which we need to follow in order to create a program to check if a number is even or odd.

  1. Declare a variable "A"
  2. Ask the user to enter the number to check if it even or odd and save it's values in above-declared variables.
  3. Now, the main logic begins, Perform A modulo 2 and check result if the output is 0
  4. If true print A is even
  5. If false print A is odd
#include <stdio.h>

int main() {
   int num;
   
   printf("Enter number to check if it's even or odd: ");
   scanf("%d",&num);
   
   if (num % 2 == 0)
      printf("%d is even\n", num);
   else
      printf("%d is odd\n", num);

   return 0;
}

Output:

Enter number to check if it's even or odd: 24
24 is even

C program to check if a number is a prime number or not

We have a great post which explains in detail about how to check if a number is a  prime number or not in C, and here is the sample code for it.

#include <stdio.h>

  void main() {
    int no, i, f;

    printf("Enter any number: ");
    scanf("%d", & no);
    f = 0;
    i = 2;
    while (i <= no / 2) {
      if (no % i == 0) {
        f = 1;
        break;
      }
      i++;
    }
    if (f == 0)
      printf(" %d is Prime Number", no);
    else
      printf("%d  Not Prime Number", no);

  }

Output:

Enter any number: 5         
5 is Prime Number

C program to swap two numbers using a Temp (third) variable

Basically, we will be swapping values of two number using the third variable, you can read the detailed post for it and here is how we will achieve this.

For example, we have two numbers(10, 20) saved in two variables (firstNumber=10 & secondNumber=20), now we need to interchange these two numbers, here interchanging means at the end of program, firstNumber =20 and secondNumber =10, so to do that we would need thrid variable Temp, to store a value temporarily. 

C program for it

#include<stdio.h>
 
void main()
{
  int firstNumber, secondNumber, Temp;
 
  //get two number from user and save it in variable firstNumber, secondNumber
  printf("\nPlease Enter the value of First Number and Second Number\n");
  scanf("%d %d", &firstNumber, &secondNumber);
 
  //print numbers before swapping them (example: firstNumber=10, secondNumber =20)
  printf("\nBefore Swapping First Number = %d and Second Number = %d\n", firstNumber,secondNumber);
 
  //save firstNuumber in temp variable (Ex: Temp= 10)
  Temp = firstNumber;

  //get secondNumber in firstNumber now (Ex: firstNumber =  20)
  firstNumber = secondNumber;

  //get the temp value in second now (Ex: secondNumber = 10 as Teamp =10)
  secondNumber = Temp;
 
//print swapped numbers
  printf("\nAfter Swapping: First Number = %d and Second Number = %d\n", firstNumber, secondNumber );
 
  
}

Output:

Please Enter the value of First Number and Second Number   
10 20                                    
                       
Before Swapping First Number = 10 and Second Number = 20  
                                                                
After Swapping: First Number = 20 and Second Number = 10

Storing values in array and printing it in C

Well in this example,we  will basically create array and ask user to enter values in it , after getting array values, we will print it using loop.

    #include <stdio.h>    
    void main()
    {
        int arr[100], n, c;
       
        //ask the user for getting array size
        printf("Enter number of elements in array\n");
        scanf("%d", &n);
       
        //ask the user for values
        printf("Enter %d elements\n", n);
       
        //saves values in array one by one until the size is reached
        for (c = 0; c < n; c++)
            scanf("%d", &arr[c]);
       
        printf("The array elements are:\n");
        //print the array
        for (c = 0; c < n; c++)
            printf("%d\n", arr[c]);
       
       
    }

I have commented out a few lines of code, to make it understandable for you.

Enter number of elements in array
5
Enter 5 elements
10 7 20 6 85
The array elements are:
10
7
20
6
85

c-program-array-sample-min.png

C program to find factorial of a number

The Factorial of a specified number refers to the product of all given series of consecutive whole numbers beginning with 1 and ending with the specified number
We use the “!” to represent factorial

Example:
5! = 1 x 2 x 3 x 4 x 5 = 120

let's C the code for the factorial

#include<stdio.h>
#include<conio.h>
 
void main()
{
    int num,f;
    clrscr();
     
    printf("\n  Enter the number: ");
    scanf("%d",&num);
     
    f=factorial(num);
    printf("\n  The factorial of the number %d is %d",num,f);
    getch();
}
 
int factorial(int number)
{
    if(number==0 || number==1)
        return 1;
    else
        return(number * fact(number-1));
}

Output:

 Enter the number: 5                                                                                                            
                                                                                                                                 
 The factorial of the number 5 is 120

If you want to read detailed article on this with various ways of factorial program you can read here : Factorial progam in C (With & without recursion)

C program to find GCD of two number

The HCF or GCD of two integers is the largest integer that can exactly divide both numbers (without a remainder). Let's create a C program for it

#include <stdio.h>
void main()
{
    int num1, num2, i, gcd;

    printf("Enter two integers: ");
    scanf("%d %d", &num1, &num2);

    for(i=1; i <= num1&& i <= num2; ++i)
    {
        // Checks if i is factor of both integers
        if(num1%i==0 && num2%i==0)
            gcd = i;
    }

    printf("G.C.D of %d and %d is %d", num1, num2, gcd);

}

Output:

Enter two integers: 5 10                                                                      
G.C.D of 5 and 10 is 5 

C program to find armstrong number

A number is armstrong number when, sum of a number's digits raised to the power total number of digits is armstrong number.

Armstrong numbers example: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 153, 370, 371, 407, 1634 etc

#include <stdio.h>

int main()
{
   int n, sum = 0, t, remainder;
   printf("\nPlease enter a number to find whether it is an armstrong or not : ");
   scanf("%d",&n);
   t = n;
   while( t != 0 )
   {
      remainder = t%10;
      sum = sum + remainder*remainder*remainder;
      t = t/10;
   }
   if ( n == sum )
      printf("\nThe number %d is an armstrong number", n);
   else
      printf("\nThe number %d is not an armstrong number", n);
   return 0;

}

Output:

Please enter a number to find whether it is an armstrong or not : 121                                             
                                                                                              
The number 121 is not an armstrong number

C program to find LCM of two numbers

The LCM of two integers n1 and n2 is the smallest positive integer that is perfectly divisible by both n1 and n2 (without a remainder). For example: the LCM of 72 and 120 is 360.

#include <stdio.h>
void main()
{
    int num1, num2, minMultiple;
    printf("Enter two positive integers: ");
    scanf("%d %d", &num1, &num2);

    // maximum number between num1 and num2 is stored in minMultiple
    minMultiple = (num1>num2) ? num1 : num2;

    // Always true
    while(1)
    {
        if( minMultiple%num1==0 && minMultiple%num2==0 )
        {
            printf("The LCM of %d and %d is %d.", num1, num2,minMultiple);
            break;
        }
        ++minMultiple;
    }
}

Output:

Enter two positive integers: 72                                                        
60                                                                                               
The LCM of 72 and 60 is 360. 

C program to print pyramid pattern

Although we have detailed article on pyramid pattern in C, I will give  a simple example here

#include <stdio.h>
int main()
{
    //declare variables to use
    int i, j, rows;
    
    //Enter the number of rows you want to print, printf shows this command to user
    printf("Enter number of rows: ");
  
    //scanf is used to get value, and save that value in 'rows' variable
    scanf("%d",&rows);

    //now loop for each row
    for(i=1; i<=rows; ++i)
    {
        //this loop will print * until value of outer loop variable(i) is greater than 
        //inner loop vairable(j)
        for(j=1; j<=i; ++j)
        {
            printf("* ");
        }
        //as soon as inner loop(j) value becomes greater than outer loop printing * ends
       // & it prints new line using \n
        printf("\n");
    }
    return 0;
}

Output:

Enter number of rows: 6                                        
*  
* *
* * * 
* * * * 
* * * * * 
* * * * * *      

C program to create simple calculator using Switch case

In this example, we will create basic functions of calculator like addtion, subtraction, multiplication and divide using +, -, %, *

# include <stdio.h>

int main() {

    char operator;
    double firstNumber,secondNumber;

    printf("Enter an operator (+, -, *,): ");
    scanf("%c", &operator);

    printf("Enter two operands: ");
    scanf("%lf %lf",&firstNumber, &secondNumber);

    switch(operator)
    {
        case '+':
            printf("%.1lf + %.1lf = %.1lf",firstNumber, secondNumber, firstNumber + secondNumber);
            break;

        case '-':
            printf("%.1lf - %.1lf = %.1lf",firstNumber, secondNumber, firstNumber - secondNumber);
            break;

        case '*':
            printf("%.1lf * %.1lf = %.1lf",firstNumber, secondNumber, firstNumber * secondNumber);
            break;

        case '/':
            printf("%.1lf / %.1lf = %.1lf",firstNumber, secondNumber, firstNumber / secondNumber);
            break;

        // operator doesn't match any case constant (+, -, *, /)
        default:
            printf("Error! operator is not correct");
    }
    
    return 0;
}

Output:

Enter an operator (+, -, *,): +                                                 
Enter two operands: 20 15                                                           
20.0 + 15.0 = 35.0 

C program to calculate simple interest using function

In this example, we will create a function which calculates Simple interest and will call this function from main method

#include<stdio.h>

float interest(int P,float R, int N)
{
     float SI;
     SI=P*R*N/100.0;
     return SI;
}      

int main()
{
     int p,n,i;
     float r,Z;
         
          printf("Enter Principal Amount : ");
          scanf("%d",&p);
          printf("Enter Interest-Rate : ");
          scanf("%f",&r);
          printf("Enter Time Period : ");
          scanf("%d",&n);
          Z=interest(p,r,n);
          printf("\nSimple-Interest : %.2f\n",Z);
        
     
     return 0;
}

Output:

Enter Principal Amount : 500                                                                            
Enter Interest-Rate : 5                                                                        
Enter Time Period : 6                                                                                      
                                                                                                          
Simple-Interest : 150.00