Calculator by function

#include<stdio.h>

int add(int x, int y );
int sub(int a, int b );
int mult(int d, int e);
int div(int g, int h);

int main(){
int num1, num2, choice;

printf("[0] Exit\n[1] Addition\n[2] Subtraction\n[3] Multiplication\n[4] Division\n");
scanf("%d", &choice);

switch(choice){
    case 0:
        exit(0);
    case 1:
        printf("Enter 1st number:");
        scanf("%d", &num1);
        printf("\nEnter 2nd number:");
        scanf("%d", &num2);
        printf("\nThe addition is:%d\n", add( num1,num2));
        break;
    case 2:
        printf("Enter 1st number:");
        scanf("%d", &num1);
        printf("\nEnter 2nd number:");
        scanf("%d", &num2);
        printf("\nThe subtraction is:%d\n", sub(num1,num2));
        break;
    case 3:
        printf("Enter 1st number:");
        scanf("%d", &num1);
        printf("\nEnter 2nd number:");
        scanf("%d", &num2);
        printf("\nThe multiplication is:%d\n", mult(num1,num2));
        break;
    case 4:
        printf("Enter 1st number:");
        scanf("%d", &num1);
        printf("\nEnter 2nd number:");
        scanf("%d", &num2);
        printf("\nThe division is:%d\n", div(num1,num2));
        break;
    default:
        printf("\nInvalid choice!!!!!!!\n");
        break;
}
}
int add(int x,int y){
    int z;
    z = x + y;
    return z;
}

int sub(int a,int b){
    int c;
    c = a - b;
    return  c;
}

int mult(int d,int e){
    int f;
    f = d * e;
    return f;
    }

int div(int g,int h){
    int i;
    i = g / h;
    return i;
}