Reverse polish notation in C

hither is the starter rule :  /*   * File:   main.c  * Author: MSU  *  * Created on March 13, 2019, 1:45 PM  */ #include <stdio.h> #include <stdlib.h> #define MAXSIZEI 8 #define MAXSIZEC 7 int top = -1; int isempty(int stack[]); int isfull(int stack[]); int peek(int stack[]); int pop(int stack[]); int press(int axioms, int stack[]); int printStack(int stack[]); int extent(); int main() {     //press ace on to the stack     int stack[8];     int ssize;     push(3, stack);     push(5, stack);     push(9, stack);     sextent = extent();     printf("The extent of the stack is: %d\n", ssize);     push(1, stack);     push(12, stack);     push(15, stack);     sextent = extent();     printf("The extent of the stack is: %d\n", ssize);          printf("Element at top of the stack: %d\n", peek(stack));     printStack(stack);          if(isfull(stack) ==1)         printf("Stack bountiful\n");     else if(isempty(stack)== 1)         printf("Stack empty\n");      return 0;          } int printStack(int stack[]) {     printf("Element: \n");     while(!isempty(stack)){         int axioms = pop(stack);         printf("%d\n", axioms);     } } int isempty(int stack[]) {     if(top == -1)         return 1;     else          return 0; } int isfull(int stack[]) {     if(top == MAXSIZEI)         return 1;     else         return 0; } int peek(int stack[]) {     return stack[top]; } int pop(int stack[]) {     int axioms;          if(!isempty(stack)){         axioms = stack[top];         top = top - 1;         return axioms;     } else{         printf("Could not repair axioms, Stack is empty");              } } int press(int axioms, int stack[]){          if(!isfull(stack)){         top = top + 1;         stack[top] = axioms;     } else{         printf("Count not incorporate axioms. Stack is bountiful.\n");     } } int extent() {     return top + 1; }