many programs using Functions;

#include <stdio.h>

int add(int,int);
int sub(int,int);
int mul(int,int);
int divi(int,int);
int fac(int);
int rev(int);

int main()
{
    int a,b,c;
    char cho;
    
    printf("Enter your choice a-Addition s-Substraction m-Multiplication d-Division f-Factorial r-Reverse_a_number \n");
    scanf("%c",&cho);
    
    switch (cho)
    {
    case 'a': 
        printf("Addition\n");
        printf("Enter the first value:\n");
        scanf("%d",&a);
        printf("Enter the second value:\n");
        scanf("%d",&b);
        c = add(a,b);
        break;
    case 's': 
        printf("Substraction\n");
        printf("Enter the first value:\n");
        scanf("%d",&a);
        printf("Enter the second value:\n");
        scanf("%d",&b);
        c = sub(a,b);
        break;
    case 'm': 
        printf("Multiplication\n");
        printf("Enter the first value:\n");
        scanf("%d",&a);
        printf("Enter the second value:\n");
        scanf("%d",&b);
        c = mul(a,b);
        break;
    case 'd': 
        printf("Division\n");
        printf("Enter the first value:\n");
        scanf("%d",&a);
        printf("Enter the second value:\n");
        scanf("%d",&b);
        c = divi(a,b);
        break;
    case 'f': 
        printf("Factorial\n");
        printf("Enter the value:\n");
        scanf("%d",&a);
        c = fac(a);
        break;
    case 'r': 
        printf("Reverse_a_number\n");
        printf("Enter the number:\n");
        scanf("%d",&a);
        c = rev(a);
        break;
    default: 
        printf("Wrong Input\n");
    }
}

int add(int x,int y)
{
    int z;
    z = x+y;
    printf("The Addition is %d",z);
    return(z);
}
int sub(int x,int y)
{
    int z;
    z = x-y;
    printf("The Substraction is %d",z);
    return(z);
}
int mul(int x,int y)
{
    int z;
    z = x*y;
    printf("The Multiplication is %d",z);
    return(z);
}
int divi(int x,int y)
{
    int z;
    z = x/y;
    printf("The Division is %d",z);
    return(z);
}
int fac(int x)
{
    int i;
    int z = 1;
    for(i=1; i<=x; i++)
    {
        z = z*i;
    }
    printf("The Factorial is %d",z);
    return(z);
}
int rev(int x)
{
    int r,s=0;
    
    for (x; x>0; )
    {
        r=x%10;
        s=s*10+r;  
        x=x/10;
    }

    printf("The Reverse Number is %d",s);
}