C语言改错题以及参考答案.doc

改错参考答案：(3)将字符串yy在屏幕上输出#includevoid main() /*Found*/ char yy100由于下面的原因，所以此处的yy不能定义成数组，所以使用指针变量 = ok?n; /*Found*/ f0r (; *yy; yy+数组名不能做赋值运算和自增运算) putchar(*yy); #includevoid main() /*Found*/ char *yy=ok?n; /*Found*/ for (; *yy; yy+) putchar(*yy); (4)计算半径为2+3的圆的面积#include#define PI 3.14/*Found*/#define S(r) PI*r*rvoid main() /*Found*/ int mianJi; mianJi = S(2+3)注意：宏定义只做替换工作。所以，用2+3去替换r，而不是用(2+3)去替换; printf(mian ji=%5.2fn, mianJi);#include#define PI 3.14/*Found*/#define S(r) PI*(r)*(r)void main() /*Found*/ float mianJi; mianJi = S(2+3); printf(mian ji=%5.2fn, mianJi);(8)打开文件d:te.c用于读并判断打开是否成功#includevoid main() FILE *fp; /*Found*/ char fileName = d:te.c; /*Found*/ fp = fopen(fileName, w); /*Found*/ if (fp = EOF) puts(File Open Error!); exit(1); putchar(fgetc(fp); fclose(fp);#includevoid main() FILE *fp; /*Found*/ char fileName = d:te.c; /*Found*/ fp = fopen(fileName, r); /*Found*/ if (fp = NULL) puts(File Open Error!); exit(1); putchar(fgetc(fp); fclose(fp);(9)申请100个字节的内存空间，显示其首地址，然后释放申请到的内存空间#include#includevoid main() /*Found*/ char p100; /*Found*/ if (p = (char *)malloc(100)p能做赋值运算，所以p不能是数组名，而应该是指针变量。 = NULL) printf(malloc memory fail!n); return ; printf(%pn, p); /*Found*/ fclose(p);#include#includevoid main() /*Found*/ char *p; /*Found*/ if (p = (char *)malloc(100) = NULL) printf(malloc memory fail!n); exit(1); printf(%pn, p); /*Found*/ free(p);(10)将字符串p显示在屏幕上#include/*Found*/#define BEGIN/*Found*/#define ENDvoid main() char *p = const用const说明的量在程序运行过程中始终保持不变，相当于常量。所以下面的i+;是错误的！ int i = 0; for (printf(n); pi; ) BEGIN putchar(pi); /*Found*/ i+;这两条语句都是循环体，所以必须用花括号括起来构成复合语句，那么花括号在哪里?此处只能是宏替换来完成这个任务了。 END#include/*Found*/#define BEGIN/*Found*/#define ENDvoid main() char *p = const int i = 0; for (printf(n); pi; ) BEGIN putchar(pi); /*Found*/ p+; END (14)调用函数swap，将a和b的值交换，最后在屏幕上显示交换后的a,b之值#include/*Found*/void swap(int x, int y函数形参中，能作出口参数的只能是数组或者是指针变量。普通变量作形参，形参的修改，不影响对应的实参。) int tmp; /*Found*/ _ *x = *y; /*Found*/ y = x;void main() int a = 3, b = 4; /*Found*/ swap(a, b); printf(a=%d b=%dn, a, b);#include/*Found*/void swap(int *x, int *y) int tmp; /*Found*/ tmp = *x; *x = *y; /*Found*/ *y = tmp;void main() int a = 3, b = 4; /*Found*/ swap(&a, &b); printf(a=%d b=%dn, a, b);(15)调用函数swap，将a和b的值交换，最后在屏幕上显示交换后的a,b之值#includevoid swap(int *x, int *y) int *tmptmp指针变量没有赋初值，所以不能使用*tmp, xy; /*Found*/ *tmp = x; *x = *y; /*Found*/ y = *tmp;void main() int a = 3, b = 4; /*Found*/ swap(*a, *b); /*Found*/ printf(a=%d b=%dn, &a, &b);#includevoid swap(int *x, int *y) int *tmp, xy; /*Found*/ xy = *x; *x = *y; /*Found*/ *y = xy;void main() int a = 3, b = 4; /*Found*/ swap(&a, &b); /*Found*/ printf(a=%d b=%dn, a, b);(16)worker的信息使用结构体存储，从键盘读入其各项信息并显示#includevoid main() struct WKER long ID; long int num; char name20; char sex; /*Found*/ ; worker.ID = 1L; /*Found*/ scanf(%d %s %s, &worker.num, , &worker.sex); /*Found*/ printf(workers info: num=%d name=%s sex=%sn, worker.num, , worker.sex);#includevoid main() struct WKER long ID; long int num; char name20; char sex; /*Found*/ worker; worker.ID = 1L; /*Found*/ scanf(%ld %s %c, &worker.num, , &worker.sex); /*Found*/ printf(workers info: num=%ld name=%s sex=%cn, worker.num, , worker.sex);(17)函数userLogin的功能主要是统计并返回登录的用户数，用户名最长30字节#include long userLogin(char *userName) /*Found*/ long userCount该局部变量根据题目的功能看，它不能每次从0开始，换句话说，它的值在该函数调用结束后还应该保留，所以该是静态变量。 = 0; userCount+; printf(welcome user %s. There have %ld users in system.n, userName, userCount); /*Found*/ return ;void main( ) /*Found*/ char *userName指针变量userName本身是不能存放字符串的。它可以指向一片空间，由那片空间来存串的内容。但是，此处它没有赋初值，即没有指向一片可用空间。; int i; while (1) printf(userName: ); scanf(%s, userName); i = userLogin(userName); #include long userLogin(char *userName) /*Found*/ static long userCount = 0; userCount+; printf(welcome user %s. There have %ld users in system.n, userName, userCount); /*Found*/ return userCount;void main( ) /*Found*/ char userName31; int i; while (1) printf(userName: ); scanf(%s, userName); i = userLogin(userName); (19)将inBuf中字符串拆分成一个个的单词这道题目算法本身难一些，但是改错的部分基本不太涉及复杂的算法，一般是赋值语句类型不匹配等比较明显的错误。/* 单词之间的分隔符由串divChar，程序中定义为“;?!,./”。 函数getStrFromBuf的功能是从Buf的开始处寻找第一个单词，将找到的单词作为一个字符串复制到Str处，divStr指明单词间的分隔符。GetStrFromBuf的返回值指向已找到单词的下一个字符。函数charInStr的功能是判断字符t是否出现在串Str中。主程序的功能是将inBuf中的所有单词在屏幕上显示出来。*/#include#define Yes 1#define No 0char *getStrFromBuf(char *Buf, char *Str, char *divStr);int charInStr(char *Str, char t);void main() char inBuf100 = how old are/ you?, *p, oneWord20; char divChar = ;?!,./; p = inBuf; while (*p) /*Found*/ getStrFromBuf(p, oneWord, divChar);该函数有返回值 if (*oneWord) puts(oneWord); int charInStr(char *Str, char t) for (; *Str; Str+) /*Found*/ if (*Str = *t关系运算左右两个操作数类型不匹配) /*Found*/ return No; /*Found*/ return Yes;char *getStrFromBuf(char *Buf, char *Str, char *divStr) for (; *Buf; Buf+) if (charInStr(divStr, *Buf) = No) break; for (; *Buf; Buf+) if (charInStr(divStr, *Buf) = Yes) break; /*Found*/ Str = *Buf; Str+; /*Found*/ *Str = 0字符串结束标记0表达错误; /*Found*/ return ;#include#define Yes 1#define No 0char *getStrFromBuf(char *Buf, char *Str, char *divStr);int charInStr(char *Str, char t);void main() char inBuf100 = how old are/ you?, *p, oneWord20; char divChar = ;?!,./; p = inBuf; while (*p) /*当p未指向字符串结束符*/ /*Found*/ p = getStrFromBuf(p, oneWord, divChar); /*让p指向当前单词后*/ /*如果找到了一个单词,即oneWord第0字符不为0。有可能找不到，例如找到前一单词you后，p指向?且未结束，再找则没有*/ if (*oneWord) puts(oneWord); /* 判断字符t是否出现在串Str中，是则返回Yes，否则返回No */int charInStr(char *Str, char t) for (; *Str; Str+) /*Found*/ if (*Str = t) /*Found*/ return Yes; /*Found*/ return No;/* 从Buf的开始处寻找第一个单词，将找到的单词作为一个字符串复制到Str处，divStr指明单词间的分隔符。返回值指向已找到单词的下一个字符。*/char *getStrFromBuf(c