Program to calculate addition,substraction,multiplication,division,modulus and exponential value

A simple calculator with functions doing addition,substraction,multiplication.and division modulus and exponential form . #include
#include
#include
#include
int add(int);
int sub(int);
int div(int);
int mul(int);
int mod(int);
int exit(void);
void main()
 {printf(“\n1.Addition.\n2.Substraction.\n3.Multiplication.\n4.Division.\n5.Modulus.\n6.Exponential Form.\n7.Exit\n\n “);
while(!(0))
{
char r;
int a,s,f,g,z,x,c,v,b,n,h,y;

scanf(“%c”,&r);
switch(r)
{
case ’1′:
int add(int);
a=add(s);
printf(“The answer is %d”,a);
break;
case ’2′:
int sub(int);
f=sub(g);
printf(“The answer is %d”,f);
break;
case ’3′:
int mul(int);
z=mul(x);
printf(“The answer is %d”,z);
break;
case ’4′:
int div(int);
c=div(n);
printf(“The answer is %d”,c);
break;
case ’5′:
int mod(int);
v=mod(b);
printf(“The answer is %d”,v);
break;
case’6′:
int exp(int);
h=exp(y);
printf(“The answer is %d”,h);
break;
case ’7′:
exit(1);
break;
}
}
getch();
}
int add(int)
{
int s,d;
printf(“Enter the numbers :”);
scanf(“%d%d”,&s,&d);
return(s+d);
}
int sub(int)
{
int s,d;
printf(“Enter the numbers:”);
scanf(“%d%d”,&s,&d);
return(s-d);
}
int mul(int)
{
int s,d;
printf(“Enter the numbers:”);
scanf(“%d%d”,&s,&d);
return(s*d);
}
int div(int)
{
int s,d;
printf(“Enter any number:”);
scanf(“%d%d”,&s,&d);
return(s/d);
}
int mod(int)
{
int s,d;
printf(“Enter any number:”);
scanf(“%d%d”,&s,&d);
return(s%d);
}
int exp(int)
{
int s,d,g;
printf(“Enter any number:”);
scanf(“%d%d”,&s,&d);
g=pow(s,d);
return(g);
}