Calculator Using Function Pointers in C

Summary: This program performs basic arithmetic operations (+, -, *, /) using function pointers. The operation to be performed is selected based on user input and invoked through the function pointer.

#include <stdio.h>

int add(int a, int b) { return a + b; }
int subtract(int a, int b) { return a - b; }
int multiply(int a, int b) { return a * b; }
int divide(int a, int b) {
    if (b != 0) return a / b;
    printf("Error: Division by zero.\n");
    return 0;
}

int main() {
    int a, b;
    char op;
    int (*operation)(int, int);

    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);

    printf("Select operation (+, -, *, /): ");
    scanf(" %c", &op);

    switch (op) {
        case '+': operation = add; break;
        case '-': operation = subtract; break;
        case '*': operation = multiply; break;
        case '/': operation = divide; break;
        default:
            printf("Invalid operation.\n");
            return 1;
    }

    int result = operation(a, b);
    printf("Result: %d\n", result);

    return 0;
}

Explanation:

Function Pointer Declaration:
The program uses a function pointer operation that can point to any arithmetic function matching the signature int func(int, int).

User Input & Dispatch:
Based on the user’s choice of operator, the function pointer is assigned the appropriate function using a switch statement.

Calling via Pointer:
The actual operation is performed through the pointer: operation(a, b), making the logic reusable and dynamic.

Division Safety:
The divide function checks for division by zero to prevent runtime errors.

Flexibility:
Using function pointers simplifies expanding the program to more operations in the future by simply adding more functions and cases.