can anyone tell why my program for solving postfix expression is not working

[jinnejeevansai]

#include<stdio.h>
struct stack{
int top;
int n[100];
}s;
void push(int a)
{
s.n[s.top+1]=a;
s.top++;
}
void pop(char a)
{
int c,b;
b=s.n[s.top];
c=s.n[s.top-1];
s.top--;
switch(a)
{
case '+':
s.n[s.top]=b+c;
break;
case '-':
s.n[s.top]=b-c;
break;
case '*':
s.n[s.top]=b*c;
break;
case '/':
s.n[s.top]=b/c;
break;
}
}
int main()
{
s.top=-1;
int m,i,j,k;
char a[100],c[100];
scanf("%d",&m);
for(i=0;i<m;i++)
{
for(j=0;j<100;j++)
{
for(k=0;;k++)
{scanf("%c",&a[k]);
if(a[k]==' ')
break;
}
if(a[0]=='+'||'-'||'*'||'/')
pop(a[0]);
else if(a[0]=='?')
break;
else
push(atoi(a));
}
printf("%d",s.n[s.top]);
}
}

[weaknessforcats]

Have you stepped through your code using your debugger? If not, this is an excellent time to learn how. Having me debug your code isn't going to help you learn how to do it.

[jinnejeevansai]

But the program is not even running .main function is also not getting executed

[weaknessforcats]

It's a problem if your code won't compile.

In this case you use atoi() but don't #include <stdlib.h>.

If your code compiles, main() will always execute

[jinnejeevansai]

for(i=0;i<m;i++) is not getting executed but why?

[weaknessforcats]

It executes on my machine.

I inserted a breakpoint at the for loop and then selected "start debugging" on Visual Studio. The debugger stopped at that breakpoint.

Does your debugger not do the same thing?