Infix-Postfix Conversion and Expression Evalution

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

char infx[max];
char pstfx[max];
char stack[max];
int nstore[max];
int nstack[max];

int top;
int cnt = 0;

int set_prcdnce(char ch)
{
 switch(ch)
 {
 case '^' : return 3;
 case '*' : return 2;
 case '/' : return 2;
 case '+' : return 1;
 case '-' : return 1;
 default  : return 0;
 }
}

int evaluate(char opt)
{
 int a,b;
 b = nstack[top]; top-=1;
 a = nstack[top];
 switch(opt)
 {
 case '^' : return pow(a,b);
 case '*' : return a*b;
 case '/' : return a/b;
 case '+' : return a+b;
 case '-' : return a-b;
 }
}

void stck_stat(char ch,int cho)
{
 int i;
 if(isalpha(ch) && cho == 2)
  {
  printf("  %d \t",nstore[cnt]);  cnt++;
  }
 else
  printf("  %c \t",ch);
 for(i=0;i<=top;i++)
  {
  if(cho==1)
   printf(" %c",stack[i]);
  else
   printf(" %d",nstack[i]);
  }
}

void main()
{
clrscr();
int flag,i,tb=0,j=0;
int cpd,ppd;
 do
 {
  flag = 0;
  printf("\n Enter the infx expression : ");
  gets(infx);
  if(strlen(infx) > max )
  {
   printf("\n\n WARNING : Exceeding the limits !! \n\n");
   flag = 1;
  }
  for(i=0;infx[i]!='\0';i++)
   {
    if(infx[i]=='(')
     tb++;
    if(infx[i]==')')
     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 its infix form : ");
puts(infx);
int x = strlen(infx);
infx[x] = ')';   infx[x+1] = '\0';
x+=1;
top = 0;
stack[top] = '(';
printf("\n\n     Element\t  Stack Status\t  Postfix Expression");
printf("\n     -------- \t ---------------  -------------------- \n\n");
for(i=0;i<strlen(infx);i++)
   {
    switch(infx[i])
    {
    case '(' :  top += 1;
stack[top] = infx[i];
break;
    case ')' :  while(stack[top] != '(')
{
pstfx[j] = stack[top];
top -= 1; j++;
}
top -= 1;
break;
    case '^' :
    case '/' :
    case '*' :
    case '+' :
    case '-' :  cpd = set_prcdnce(infx[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] = infx[i];
break;
    default :   pstfx[j] = infx[i]; j++;
break;
    }
   printf("  %-2d. ",i+1);
   stck_stat(infx[i],1);
   gotoxy(40,11+i);
   puts(pstfx);
   }
pstfx[j] = '\0';
printf("\n\n The expression in postfix form : ");
puts(pstfx);
j=0;
for(i=0;i<strlen(pstfx);i++)
 {
  if(isalpha(pstfx[i]))
   {
     printf("\n Enter value for %c :",pstfx[i]);
     scanf("%d",&nstore[j]);  j++;
   }
 }

j=0;
printf("\n\n Now, The postfix expression becomes as : ");
for(i=0;i<strlen(pstfx);i++)
 {
  if(isalpha(pstfx[i]))
   {
     printf("%d,",nstore[j]);  j++;
   }
  else
   printf("%c,",pstfx[i]);
 }
printf("\n\n Evaluating the stack as follows : ");
printf("\n\n Element Check \t Stack Status");
printf("\n ----------- \t ------------ \n");
j = 0;   top = -1;
for(i=0;i<strlen(pstfx);i++)
 {
 printf("\n %-2d ",i+1);
 switch(pstfx[i])
    {
    case '^' :
    case '/' :
    case '*' :
    case '+' :
    case '-' :  nstack[top] = evaluate(pstfx[i]);
break;
    default :   top +=1; nstack[top] = nstore[j]; j+=1;
break;
    }
 stck_stat(pstfx[i],2);
 }
printf("\n\n After, Evaluating the expression the result is : %d",nstack[top]);
getch();
}