Balanced Expression

Write A C Program To Check Whether A Given Expression is balanced
In Case Of Parenthesis

Source Code:

#include<stdio.h>
#include<conio.h>
#include<string.h>
#include<stdlib.h>

void main()
{
 char stk[100],exp[100];
 int i,top;
 top=-1;
 clrscr();
 printf("enter an expression\n");
 gets(exp);

 for(i=0;exp[i]!='\0';i++)
 {
  if(exp[i]=='('||exp[i]=='{'||exp[i]=='[')
  {
   top=top+1;
   stk[top]=exp[i];
  }
  else
   if(exp[i]==')')
   {
    if(stk[top]=='(')
    {
     top--;
    }
    else
    {
    printf("unbalanced expression");
    exit(0);
    }
   }
  else
   if(exp[i]=='}')
   {
    if(stk[top]=='{')
    {
     top--;
    }
    else
    {
    printf("unbalanced expression");
    exit(0);
    }
   }
  else

   if(exp[i]==']')
   {
    if(stk[top]=='[')
    {
     top--;
    }
    else
    {
    printf("unbalanced expression");
    exit(0);
    }
   }
 }

  if(top==-1)
  {
   printf("expression is balanced\n");
  }
  else
  {
   printf("expression is not balanced\n");
  }
 getch();
}

output:

enter an expression
 1+2*(2+3)+{4+5}
 expression is balanced

 enter an expression
(1+2)*{2*3{
expression is not balanced