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C Program to Make a Simple Calculator

In this article, you will learn about creating a simple calculator program in C. A simple calculator is a calculator that performs four basic mathematical operations such as addition, subtraction, multiplication, and division. Here, the calculator program is created in two ways:

In C programming, to make a simple calculator that can do the four most basic math operations, use the switch case to figure out which input operator to use for each calculation, as shown in the program below.

C Calculator Program with Switch Case

Here is a simple menu-driven program based on simple calculations like addition, subtraction, multiplication, and division according to the user's choice:

#include<stdio.h>
#include<conio.h>
int main()
{
   float num1, num2, res;
   int choice;
   do
   {
      printf("1. Addition\n");
      printf("2. Subtraction\n");
      printf("3. Multiplication\n");
      printf("4. Division\n");
      printf("5. Exit\n\n");
      printf("Enter Your Choice(1-5): ");
      scanf("%d", &choice);
      if(choice>=1 && choice<=4)
      {
         printf("\nEnter any two Numbers: ");
         scanf("%f %f", &num1, &num2);
      }
      switch(choice)
      {
         case 1:
            res = num1+num2;
            printf("\nResult = %0.2f", res);
            break;
         case 2:
            res = num1-num2;
            printf("\nResult = %0.2f", res);
            break;
         case 3:
            res = num1*num2;
            printf("\nResult = %0.2f", res);
            break;
         case 4:
            res = num1/num2;
            printf("\nResult = %0.2f", res);
            break;
         case 5:
            return 0;
         default:
            printf("\nWrong Choice!");
            break;
      }
      printf("\n------------------------\n");
   }while(choice!=5);
   getch();
   return 0;
}

This program was built and runs in the Code::Blocks IDE. Here is the initial snapshot of the sample run:

c program to make simple calculator

Now supply any input (as a choice from 1 to 5) in a way that:

Let's suppose the user enters 2 as his/her choice, so the program will ask again to enter any two numbers to perform the subtraction. For instance, if the user enters 2 as a choice and 20 as the first number, followed by 10 as the second number. Press the ENTER key to see the output as shown in the snapshot given below:

c calculator program

Press 5 to exit the calculation process. Let's take a look at the explanation of this program.

Program Explained

Create a simple calculator using a C function

After understanding the above program, it is easy to create the same program using functions. So here is the calculator program that uses functions in C.

#include<stdio.h>
#include<conio.h>
float addFun(float, float);
float subFun(float, float);
float mulFun(float, float);
float divFun(float, float);
int main()
{
   float num1, num2, res;
   int choice;
   do
   {
      printf("1. Addition\n");
      printf("2. Subtraction\n");
      printf("3. Multiplication\n");
      printf("4. Division\n");
      printf("5. Exit\n\n");
      printf("Enter Your Choice(1-5): ");
      scanf("%d", &choice);
      if(choice>=1 && choice<=4)
      {
         printf("\nEnter any two Numbers: ");
         scanf("%f %f", &num1, &num2);
      }
      switch(choice)
      {
         case 1:
            res = addFun(num1, num2);
            printf("\nResult = %0.2f", res);
            break;
         case 2:
            res = subFun(num1, num2);
            printf("\nResult = %0.2f", res);
            break;
         case 3:
            res = mulFun(num1, num2);
            printf("\nResult = %0.2f", res);
            break;
         case 4:
            res = divFun(num1, num2);
            printf("\nResult = %0.2f", res);
            break;
         case 5:
            return 0;
         default:
            printf("\nWrong Choice!");
            break;
      }
      printf("\n------------------------\n");
   }while(choice!=5);
   getch();
   return 0;
}
float addFun(float a, float b)
{
   return (a+b);
}
float subFun(float a, float b)
{
   return (a-b);
}
float mulFun(float a, float b)
{
   return (a*b);
}
float divFun(float a, float b)
{
   return (a/b);
}

Here is a sample run of the above program:

c calculator program using function

All four functions in this example accept two floating-point values as arguments, perform the operation, and then return the result to the main() function. That is, its return value gets initialized to the res variable.

The same program in different languages

C Quiz

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