例110：实现链表
#include <stdio.h> #include <stdlib.h> int main(int argc, char const *argv[]) { int i; // 定义结构、声明头指针和临时节点 struct ListEntry { int number; struct ListEntry *next; } start, *node; // 初始化链表 start.next = NULL; node = &start; for (i = 1; i <= 10; i++) { node->next = (struct ListEntry *) malloc(sizeof(struct ListEntry)); node = node->next; node->number = i; node->next = NULL; } // 节点指向头节点 node = start.next; while (node) { printf("%d ", node->number); node = node->next; } return 0; }例111：双向链表的插入元素
#include <stdio.h> #include <stdlib.h> int main(int argc, char const *argv[]) { int i; struct ListEntry { int number; struct ListEntry *next; struct ListEntry *previous; } start, *node, *new; start.next = NULL; start.previous = NULL; node = &start; // 生成链表节点为1,3,5,7,9 for (i = 1; i < 10; i += 2) { node->next = (struct ListEntry *) malloc(sizeof(struct ListEntry)); node->next->previous = node; node = node->next; node->number = i; node->next = NULL; } for (i = 2; i <= 10; i += 2) { int found = 0; new = (struct ListEntry *) malloc(sizeof(struct ListEntry)); new->number = i; node = start.next; do { // 如果原链表节点大于新节点的数就将新节点插入该节点前面 if (node->number > new->number) { new->next = node; new->previous = node->previous; node->previous->next = new; node->previous = new; found = 1; } else node = node->next; }while ((node->next) && (! found)); // 最后一个节点 if (! found) if (node->number > new->number) { new->next = node; new->previous = node->previous; node->previous->next = new; node->previous = new; } else { new->next = NULL; new->previous = node; node->next = new; } } /* Display the list*/ node = start.next; do { printf("%d ", node->number); node = node->next; }while (node); return 0; }例112：main函数的参数
#include <stdlib.h> #include <stdio.h> /** * main函数 - 程序入口 * @Author dust_fall * @param argc 参数的个数，这个在程序运行时输入的命令行中字符串的个数决定。 * @param argv 具体的参数，每个参数是一个字符数组指针。 * @param env 环境变量参数，由系统的当前环境变量的设置决定。 * @return 返回给系统的值 */ int main(int argc, char *argv[], char *env[]) { printf("Command line\n"); while (*argv) puts(*argv++); printf("Environment entries\n"); while (*env) puts(*env++); return 0; }例113：一段我编译不了的代码
#include <stdio.h> #include <dos.h> int main(int argc, char const *argv[]) { if (_8087) printf("Math coprocessor found\n"); else printf("No math coprocessor\n"); return 0; }例114：switch选择结构的使用
#include <stdio.h> int main(int argc, char const *argv[]) { int a = 1, b, c, d; switch (a) { case 1: a = 5; b = 6; c = 7; d = 8; break; case 2: b = 6; c = 7; d = 8; break; }; printf("a=%d b=%d c=%d d=%d\n", a, b, c, d); // a=5 b=6 c=7 d=8 return 0; }例115：又一段我编译不了的代码
#include <stdio.h> #include <dos.h> #include <dir.h> int function[255]; /* DOS services*/ void interrupt far (*original_handler)(); void interrupt far handler(void) { char i; asm { mov i, ah } function[i]++; _chain_intr(original_handler); } void main(void) { int i; // Zero the function counts for (i = 0; i < 255; i++) function[i] = 0; original_handler = _dos_getvect(0x21); _disable(); _dos_setvect(0x21, handler); _enable(); printf("This is a message\n"); fprintf(stdout, "This is a second message\n"); printf("Current disk is %c\n", getdisk() + 'A'); _disable(); _dos_setvect(0x21, original_handler); _enable(); for (i = 0; i <= 255; i++) if (function[i]) printf("Function %x called %d times\n", i, function[i]); }例116：还有一段我编译不了的代码
#include <stdio.h> #include <dos.h> void main(void) { printf("Previous extended Ctrl-Break status %s\n", (getcbrk()) ? "On": "Off"); setcbrk(0); /* Turn if off*/ }例117：还有。。。
#include <stdio.h> #include <dos.h> #include <conio.h> void far handler(unsigned device_error, unsigned error_code, unsigned far *device_header) { cputs("Critical error ending program\n"); _hardresume(_HARDERR_ABORT); /* Abort*/ } void main(void) { FILE *fp; _harderr(handler); fp = fopen("A:SOMEFILE.EXT", "r"); printf("Program message...\n"); fclose(fp); }例118：区分ASCII码表中的不可打印字符和可打印字符
#include <stdio.h> #include <ctype.h> int main(int argc, char const *argv[]) { int ascii_char; // 区别ASCII码表的可打印字符 for (ascii_char = 0; ascii_char < 128; ascii_char++) // int isprint(int c) 检查所传的字符是否是可打印的。可打印字符是非控制字符的字符 // 如果 c 是一个可打印的字符，则该函数返回非零值（true），否则返回 0（false） if (isprint(ascii_char)) printf("ASCII value %d setting (hex) %x ASCII %c\n", ascii_char, _ctype[ascii_char], ascii_char); else printf("ASCII value %d setting (hex) %x ASCII %c\n", ascii_char, _ctype[ascii_char], ascii_char); return 0; }例119：双向链表的遍历
#include <stdio.h> #include <malloc.h> int main(int argc, char const *argv[]) { int i; struct ListEntry { int number; struct ListEntry *next; struct ListEntry *previous; } start, *node; // 建立并初始化双向链表 start.next = NULL; start.previous = NULL; node = &start; for (i = 1; i <= 10; i++) { node->next = (struct ListEntry *) malloc(sizeof(struct ListEntry)); node->next->previous = node; node = node->next; node->number = i; node->next = NULL; } node = start.next; // 正向遍历链表 do { printf("%d ", node->number); node = node->next; } while (node->next); // 逆向遍历链表 do { printf("%d ", node->number); node = node->previous; } while (node->previous); return 0; }例120：打印错误信息
#include <stdio.h> #include <stdlib.h> int main(int argc, char const *argv[]) { int error; for (error = 0; error < sys_nerr; error++) printf("Error %d %s\n", error, sys_errlist[error]); return 0; }例121：调用子进程
#include <process.h> #include <stdio.h> int main(int argc, char const *argv[]) { printf("About to call child process\n\n"); // int execl(char *pathname, char *arg0, arg1, ..., argn, NULL); // execl()用来执行参数pathname字符串所代表的文件路径, // 接下来的参数代表执行该文件时传递过去的argv(0),argv[1], ..., 最后一个参数必须用空指针(NULL)作结束 execl("CHILD.EXE", "CHILD.EXE", "AAA", "BBB", "CCC", NULL); printf("\n\nBack from child process--SHOULD NOT APPEAR\n"); return 0; }例122：调用子进程2
#include <process.h> #include <stdio.h> int main(int argc, char const *argv[]) { // 这里定义的数组最后一个元素是NULL, 加入参数列表后, 最后一个参数是NULL char *env[] = {"FILE=EXECLPE.C", "LANGUAGE=C", "OS=DOS", NULL}; // int execple(char *pathname, char *arg0, arg1, ..., NULL, char *envp[]); // execple()会从PATH 环境变量所指的目录中查找符合参数file 的文件名, 找到后便执行该文件, // 然后将第二个以后的参数当做该文件的argv[0], argv[1], ..., 最后一个参数必须用空指针(NULL)作结束. execlpe("CHILD.EXE", "CHILD.EXE", "Using-spawnlpe", "BBB", NULL, env); return 0; }例123：调用子进程3
#include <stdio.h> #include <process.h> int main(int argc, char const *argv[]) { char *env[] = { "FILENAME=SPAWNVXX.C", "OS=DOS", "ROUTINE=EXECVPE", NULL }; char *argv[] = { "CHILD.EXE", "AAA", "BBB", NULL }; // int execvpe(char *pathname, char *argv[], char *envp[]); execvpe("CHILD.EXE", argv, env); return 0; }