Language: C

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAX 100

int top, s[MAX];

void initialize();
int isEmpty();
int isFull();
void push(int);
char pop();

int main(){
  int x, y;
  char s[MAX];

  initialize();#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAX 100

int top, s[MAX];

void initialize();
int isEmpty();
int isFull();
void push(int);
char pop();

int main(){
  int x, y;
  char s[MAX];

  initialize();

  while(scanf("%s", s) != EOF ){
    
    if (s[0] == '+' ){
      x = pop();
      y = pop();
      push(x + y);
    }
    else if (s[0] == '-' ){
      y = pop();
      x = pop();
      push(x - y);
    }
    else if (s[0] == '*' ){
      x = pop();
      y = pop();
      push(x * y);
    }
    else {
      push(atoi(s));
    }
  }

  printf("%d\n", pop());

  return 0;
}

void initialize(int top){
  top = 0;
}

int isEmpty(int top){
  if(top == 0)  return 0;
  else return 1;
}

int isFull(int top){
  if(top >= MAX -1)  return 0;
  else return 1;
}

void push(int x){
  if(isFull(top) == 0)   printf("??¨?????????????????????????????????\n");
  else{
    top++;
    s[top] = x;
  }
}
  
char pop(){
  if(isEmpty(top) == 0) printf("??¨???????????¢?????????????????????\n");
  else top--; 
  return s[top+1];
}

  while(scanf("%s", s) != EOF ){
    
    if (s[0] == '+' ){
      x = pop();
      y = pop();
      push(x + y);
    }
    else if (s[0] == '-' ){
      y = pop();
      x = pop();
      push(x - y);
    }
    else if (s[0] == '*' ){
      x = pop();
      y = pop();
      push(x * y);
    }
    else {
      push(atoi(s));
    }
  }

  printf("%d\n", pop());

  return 0;
}

void initialize(int top){
  top = 0;
}

int isEmpty(int top){
  if(top == 0)  return 0;
  else return 1;
}

int isFull(int top){
  if(top >= MAX -1)  return 0;
  else return 1;
}

void push(int x){
  if(isFull(top) == 0)   printf("??¨?????????????????????????????????\n");
  else{
    top++;
    s[top] = x;
  }
}
  
char pop(){
  if(isEmpty(top) == 0) printf("??¨???????????¢?????????????????????\n");
  else top--; 
  return s[top+1];
}

Compiler output:
main.c: In function 'main':
main.c:18:16: error: stray '#' in program
   18 |   initialize();#include<stdio.h>
      |                ^
main.c:18:17: error: 'include' undeclared (first use in this function)
   18 |   initialize();#include<stdio.h>
      |                 ^~~~~~~
main.c:18:17: note: each undeclared identifier is reported only once for each function it appears in
main.c:18:25: error: 'stdio' undeclared (first use in this function); did you mean 'stdin'?
   18 |   initialize();#include<stdio.h>
      |                         ^~~~~
      |                         stdin
main.c:23:1: error: expected expression before 'int'
   23 | int top, s[MAX];
      | ^~~
main.c:64:6: error: static declaration of 'initialize' follows non-static declaration
   64 | void initialize(int top){
      |      ^~~~~~~~~~
main.c:25:6: note: previous declaration of 'initialize' with type 'void()'
   25 | void initialize();
      |      ^~~~~~~~~~
main.c:68:5: error: static declaration of 'isEmpty' follows non-static declaration
   68 | int isEmpty(int top){
      |     ^~~~~~~
main.c:26:5: note: previous declaration of 'isEmpty' with type 'int()'
   26 | int isEmpty();
      |     ^~~~~~~
main.c:73:5: error: static declaration of 'isFull' follows non-static declaration
   73 | int isFull(int top){
      |     ^~~~~~
main.c:27:5: note: previous declaration of 'isFull' with type 'int()'
   27 | int isFull();
      |     ^~~~~~
main.c:78:6: error: static declaration of 'push' follows non-static declaration
   78 | void push(int x){
      |      ^~~~
main.c:28:6: note: previous declaration of 'push' with type 'void(int)'
   28 | void push(int);
      |      ^~~~
main.c:86:6: error: static declaration of 'pop' follows non-static declaration
   86 | char pop(){
      |      ^~~
main.c:29:6: note: previous declaration of 'pop' with type 'char()'
   29 | char pop();
      |      ^~~