# Program to simulate calculator using switch in C

The input is the expression of the form (a op b) where a and b are the operands and op is an operator. For example 10+20. Based on the operator, the operation is performed and the result is displayed. The complete algorithm along with the flowchart is shown below:

Algorithm: CALCULATOR

Step 1: [Read expression of from (a+b)]
Step 2: [perform the required operation]
switch(op)

case "+" : res = a+b
case "-" : res = a-b
case "*" : res= a*b
case "/" : if (b==0)
Write : "Divide by 0"
Exit
else

res = a/b
[End of if]
default : Write: ' Invalid operator'
Exit
[End of switch]
Step 3: [Output the result]
Write: res
Step 4: [Finished]
Exit.

The equivalent C program to perform various operations such as addition, subtraction, multiplication and division is shown below:

### Program

#include<stdio.h>
#include<process.h>
main( )
{
int a, b, res;
char op; /* can be +, - , *,, or / */
printf("Enter the expression");
scanf("%d%c%d",&a, &op, &b);
switch(op)
{
case '+' :
res = a+b;
break;
case '-':
res= a-b;
break;
case '*':
res=a*b;
break;
case '/' :
if(b!=0)
res=a/b;
else
{
printf("Div by 0\n");
exit(0);
}
default:
printf("Invalid operator \n");
}
/* end of switch statement */
printf("%d %c %d = %d\n",a,op,b,res);  /* Display the result */
}

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