Infix to postfix

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

char stack[50];
int top = -1;
void in_to_post(char infix[]);
void push(char ch);
char pop();

void main() {
 char infix[25];
 clrscr();
 printf("Enter the infix expression:");
 gets(infix);
 in_to_post(infix);
 getch();
}

void push(char symb)  {
 if (top >= 49) {
  printf("Stack overflow!");
  getch();
  return;
 } else {
  top++;
  stack[top]=symb;
 }
}

char pop() {
 char item;
 if (top == -1) {
  printf("Stack empty!");
  getch();
  return (0);
 } else {
  item = stack[top];
  top--;
 }
 return(item);
}

int preced(char ch) {
 if (ch==47)
  return (5);
 else if (ch==42)
  return (4);
 else if (ch == '+' || ch == '-')
  return (3);
 else
  return (2);
}

void in_to_post(char infix[]) {
 int length;
 static int index = 0, pos = 0;
 char symbol, temp;
 char postfix[40];
 length = strlen(infix);
 push('#');
 while (index < length) {
  symbol = infix[index];
  switch (symbol) {
   case '(':  push(symbol); break;
   case ')':  temp = pop();
      while (temp != '(') {
      postfix[pos]= temp;
      pos++;
      temp = pop();
      }
      break;
   case '+':
   case '-':
   case '*':
   case '/':
   case '^':
      while (preced(stack[top]) >= preced(symbol)) {
      temp = pop();
      postfix[pos] = temp;
      pos++;
      }
      push(symbol);
      break;
   default: postfix[pos++] = symbol; break;
  }
  index++;
 }
 while (top > 0) {
  temp = pop();
  postfix[pos++] = temp;
 }
 postfix[pos++] = '\0';
 puts(postfix);
 return;
}