求个程序，希望高手帮忙,该怎么解决

/*
  an easy calculator

  author He Zhengjun 

  2011-3-30
*/


#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>

#define MAX 20

int pri(int);

void initial();

int stack[MAX]={0};

int input[MAX]={0};

int top=-1;

int itop=-1;

int flag[MAX]={0};

int i=0;

void main()
{
    char c[30];
    printf("\n\n\n\t Welcome to use easy Calculate\t\n\t Don't input blanks in your input strings\n\t for it to work correctly\t\n \n\tThanks!\t\n");

    printf("\tNOTICE:\n");

    printf("\tq or Q mins quit the mini calculator\n");
    
    while(1)
    {
        initial();

        scanf("%s",c);
        
        if(c[0]=='q' || c[0]=='Q')
        {
            char t;
            printf("Do you want to quit?(y/n):");

            fflush(stdin);
            scanf("%c",&t);

            if(t=='y' || t== 'Y')
            {
                break;
            }else{
                continue;
            }
        }

        int len=strlen(c);
        
        while(i<len)
        {
            if(c[i]==' ')
            {
                i++;
                continue;
            }
            if(pri(c[i])>=0)
            {
                if(top==-1 || pri(stack[top])<pri(c[i]) || c[i]=='(')
                {
                    stack[++top]=c[i];
                }
                else 
                {
                    while(stack[top]!='(' && pri(m.D