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

#define  NUM  30
int    student[NUM];        
int    n=0;                    
int flag=0;                    
                           
int create();

main()
{   
    int menuchoice;
                     
   
    system("color f0");
    printf("\n\n\n\n");
    printf("\t\t\t数组基本功能菜单        \n");
    printf("\t\t\t  作者：* * *            \n");
    printf("\t\t\t  ============        \n");
    printf("\t\t\t  1.建立成绩数组        \n");
    printf("\t\t\t  2.显示成绩数组        \n");
    printf("\t\t\t  3.按给定成绩查找    \n");
    printf("\t\t\t  4.按顺序号查找        \n");
    printf("\t\t\t  5.从高到低排序输出    \n");
    printf("\t\t\t  6.从低到高排序输出    \n");
    printf("\t\t\t  7.给定顺序号插入成绩\n");
    printf("\t\t\t  8.给定顺序号删除成绩\n");
    printf("\t\t\t  9.给定顺序号修改成绩\n");
    printf("\t\t\t  10.结束程序            \n");
    printf("\t\t\t  ============        \n");
                                            
                                       
                                
   
   
    printf("\t\t\t请输入您的选择：        \n");   
   
   
    scanf("%d",&menuchoice);

    switch(menuchoice)   
    {
              case 1: if (flag=1)
                        printf("已经执行过该功能,不能继续执行该功能,按任意键继续");
                    else
                        if (flag=0)
                            printf("输入成绩数组的个数:");
                            do
                            {
                                scanf("%d",&n);
                            }
                            while(n>0&&n<=30);
                            create();
        }
    }

int create()
{
    int i,n;
    for (i=1;i<=n;i++)
        scanf("%d",&student[NUM]);
}只是case1部分的，不知道那里错了，求大神。

//if (flag = 1) 这是在赋值，不是作比较。
        if (flag == 1)
        {
        }
        else if(flag == 0)
        {
        }

        //每个case语句块，结尾加上break
        switch(menuchoice)
        {
            case 1:
                {
                    break;
                }
            case 2:
                {
                    break;
                }
            default:
                {
                    break;
                }
        }
    

// while(n>0&&n<=30); 这种条件判断，子条件最好加上()
         while( (n > 0) && (n <=30 ) )
        {
        }