Tente estudar abaixo vou te mandar um codigo em C para vc ter uma ideia
#include <stdio.h>
void main()
{
double number1 = 0.0; /* First operand value a decimal number */
double number2 = 0.0; /* Second operand value a decimal number */
char operation = 0; /* Operation - must be +, -, *, /, or % */
char answer = 0; /* Added to store answer for continuing */
start: /* Label added for goto destination */
printf("\nEnter the calculation as number operator number\n"); /*Modified */
scanf("%lf %c %lf", &number1, &operation, &number2);
/* Code to check the input goes here */
switch(operation)
{
case '+': /* No checks necessary for add */
printf("= %lf\n", number1 + number2);
break;
case '-': /* No checks necessary for subtract */
printf("= %lf\n", number1 - number2);
break;
case '*': /* No checks necessary for multiply */
printf("= %lf\n", number1 * number2);
break;
case '/':
if(number2 == 0) /* Check second operand for zero */
printf("\n\n\aDivision by zero error!\n");
else
printf("= %lf\n", number1 / number2);
break;
case '%': /* Check second operand for zero */
if((long)number2 == 0)
printf("\n\n\aDivision by zero error!\n");
else
printf("= %ld\n", (long)number1 % (long)number2);
break;
default: /* Operation is invalid if we get to here */
printf("\n\n\aIllegal operation!\n");
}
/* The following statements added to prompt for continuing */
printf("\n Do you want to do another calculation? (y or n): ");
scanf(" %c", &answer);
if(answer == 'y' || answer == 'Y')
goto start; /* Go back to the beginning */
