Classic calculator code in c++

#include<iostream.h>
void main()
{
int a,b,c=0,i,r=0;
char ch;
cout<<"enter the first number\n";
cin>>a;
cout<<"enter the second number\n";
cin>>b;
cout<<"Enter (+) For Sum \n\n Enter(-) For Subtracion \n\nEnter(*) For Multiplaction\n\n Enter(/) For Division \n\n Enter(%) For Mod\n\nEnter (i) For Inverse of First Number";
cin>>ch;
// if(ch=='+' || ch=='-' || ch=='*' || ch=='/' || ch=='%' || ch=='i')
{
switch (ch){
case '+':
for (i=1 ; i<=b ;i++)
{
a+=1;
}
cout<<a<<endl;
break;

case '-':
for (i=1;i<=b;i++)
{
a-=1;
}
cout<<a<<endl;
break;
case '*':
for(i=1;i<=b;i++)
{
r+=a;
}
cout<<r<<endl;
break;

case '/':


while(a>=b)
{
for(i=1;i<=b;i++)
{
a=--a;
}
c++;
}
cout<<c<<endl;
case '%':
while(a>=b)
{
for(i=1;i<=b;i++)
{
a=--a;
}
}
cout<<a<<endl;
case 'i':
while(a)
{
--a;
--c;
}
cout<<c<<endl;
default:
cout<<"plese enter the correct character[+,-,*,/,%,i]"<<endl;
}
}
}