Argument But No Returning Type Program

#include<stdio.h>
#include<conio.h>
void multi(int,int);
void main()
{
int a,b;
clrscr();
printf("Enter the numbers: ");
scanf("%d %d",&a,&b);
multi(a,b);
getch();
}
void multi(int p,int q)
{
int m;
m=p*q;
printf("The multiplication of two number is: %d",m);
}

No Argument but Returning type function

#include<stdio.h>
#include<conio.h>
int add();
void main()
{
int m;
clrscr();
m=add();
printf("The sum is : %d",m);
getch();
}
int add()
{
int a,b,s=0;
printf("Enter the number: ");
scanf("%d %d",&a,&b);
s=a+b;
return s;
}