Infix-Postfix Coversion

#include<stdio.h>
#include<conio.h>
#include<string.h>
#define max 50

char exprsn[max];
char pstfx[max];
char stack[max];
int set_prcdnce(char ch)
{
 switch(ch)
 {
 case '^' : return 5;
 case '*' : return 4;
 case '/' : return 4;
 case '+' : return 3;
 case '-' : return 3;
 default  : return 0;
 }
}

void main()
{
clrscr();
int flag,i,top=0,tb=0,j=0;
int cpd,ppd;
 do
 {
  flag = 0;
  printf("\n Enter the expression : ");
  gets(exprsn);
  if(strlen(exprsn) > max )
  {
   printf("\n\n WARNING : Exceeding the limits !! \n\n");
   flag = 1;
  }
  for(i=0;exprsn[i]!='\0';i++)
   {
    if(exprsn[i]=='(')
     tb++;
    if(exprsn[i]==')')
     tb--;
   }
  printf("\n\ntb = %d\n",tb);
  if(tb != 0)
  {
   printf("\n\n WARNING : Unequal Right n Left Brackets in the expression !! \n\n");
   flag = 1;
  }
 }while(flag == 1);
printf("\n\n The expression in normal form : ");
puts(exprsn);
int x = strlen(exprsn);
exprsn[x] = ')';
exprsn[x+1] = '\0';
//printf("\n%c\n",exprsn[x]);
x+=1;
stack[top] = '(';
for(i=0;i<=x;i++)
   {
    switch(exprsn[i])
    {
    case '(' :  top += 1;
stack[top] = exprsn[i];
break;
    case ')' :  while(stack[top] != '(')
{
pstfx[j] = stack[top];
top -= 1; j++;
}
top -= 1;
break;
    case '^' :
    case '/' :
    case '*' :
    case '+' :
    case '-' :  cpd = set_prcdnce(exprsn[i]);
ppd = set_prcdnce(stack[top]);
if(cpd < ppd)
{
while(cpd<=ppd)
{
if(top == -1) break;
pstfx[j] = stack[top];
top -= 1; j++;
ppd = set_prcdnce(stack[top]);
}
}
top += 1; stack[top] = exprsn[i];
break;
    default :   pstfx[j] = exprsn[i]; j++;
break;
    }
   }
pstfx[j] = '\0';
printf("\n\n The expression in postfix form : ");
puts(pstfx);
getch();
}