C code to convert INFIX expression into POSTFIX expression

//C program to convert given INFIX expression into POSTFIX expression using stack//

#include<stdio.h>
#include<conio.h> 
#include<string.h>
#define MAX 20

char stack[MAX];
int top=-1;
char pop();
void push(char item);

int prcd(char symbol)
{
switch(symbol)
{
case +:
case -:return 2;
break;
case *:
case /:return 4;
break;
case ^:
case $:return 6;
break;
case (:
case ):
case #:return 1; 
break;
}
}
 
int isoperator(char symbol)
{
switch(symbol) 
{
case +:
case -:
case *:
case /:
case ^:
case $:
case (:
case ):return 1;
break;
default:return 0;
}
}

 
void convertip(char infix[],char postfix[])
{
int i,symbol,j=0;
stack[++top]=#;
for(i=0;i<strlen(infix);i++)
{
symbol=infix[i];
if(isoperator(symbol)==0)
{
postfix[j]=symbol;
j++;
}
else{ 
if(symbol==()
push(symbol); 
else
if(symbol==))
{
while(stack[top]!=()
{ 
postfix[j]=pop();
j++; 
}
pop();//pop out 
}

else{
if(prcd(symbol)>prcd(stack[top]))
push(symbol);
else{
while(prcd(symbol)<=prcd(stack[top]))
{
postfix[j]=pop();
j++;
}
push(symbol);

}//end of else.

}//end of else.

}//end of else.

}//end of for.

while(stack[top]!=#)
{
postfix[j]=pop();
j++;
}
postfix[j]=

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