24点扑克游戏,弄着玩玩的,有问题请多指教

				#define LENGTH 80
				char ch[LENGTH],op[LENGTH];
				int chptr=0;
				int opptr=0;
				
				void main()
				{
					extern char push(),pop();
					extern void postfix();
					char expr[LENGTH];
					int i;
				
					printf("Expression=");
					scanf("%s",&expr);
					postfix(expr);
					for(i=1;i						printf("%c",ch[i]);
				}
				
				void postfix(char s[])
				{
					int i=0;
					char temp;
					extern char op[],ch[];
					extern int opptr,chptr;
					while(s[i]!='\0')
					{
						switch(s[i])
						{
						case '(':
							push(op,&opptr,s[i]);
							break;
						case ')':
							do
							push(ch,&chptr,pop(op,&opptr));
							while(op[opptr]!='(' && opptr>=1);
							pop(op,&opptr);
							break;
						case '*':
						case '/':
							if(opptr>0)
								while(opptr>0 && (op[opptr]=='*'||op[opptr]=='/'))
									push(ch,&chptr,pop(op,&opptr);
								push(op,&opptr,s[i]);
								break;
						case '+':
							if(opptr>0)
								while(op[opptr]!='(' && opptr>0)
									push(ch,&opptr,s[i]);
								break;
						default:
							push(ch,&chptr,s[i]);
							break;
						}
						i++;
					}
					for(i=opptr;i>=1;i--)
						if((temp==pop(op,&opptr))!='(')
							push(ch,&chptr,temp);
				}
				
				char pop(char array[],int *index)
				{
					char temp;
					temp=array[*index];
					(*index)--;
					return(temp);
				}
				
				char push(char array[],int *index,char ch)
				{
					++(*index);
					array[*index]=ch;
				}