C program to convert binary number into decimal number and vice versa

#include<stdio.h>
#include<conio.h>
#include<math.h>
int n,s=0,m=0;
int bin_to_dec()
{
puts("Enter the binary number");
scanf("%d",&n);
while(n!=0)
{
s=s+(n%10)*pow(2,m);
n=n/10;
m++;
}
return s;
}
int dec_to_bin()
{
puts("Enter the decimal nunber");
scanf("%d",&n);
while(n!=0)
{
s=s+(pow(10,m)*(n%2));
m++;
n=n/2;
}
return s;
}
void main()
{
int ch,r;
puts("Enter 1 for binary to decimal");
puts("Enter 2 for decimal to binary");
puts("Enter your choice");
scanf("%d",&ch);
switch(ch)
{
case 1:r=bin_to_dec();
printf("Decimal = %d",r);
break;
case 2:
r=dec_to_bin();
printf("Binary = %d",r);
break;
default:puts("Enter 1 or 2");
}
}