m.txt

C语言函数大全

main()主函数  
    每一C 程序都必须有一main()函数, 可以根据自己的爱好把它放在程序的某  
个地方。有些程序员把它放在最前面, 而另一些程序员把它放在最后面, 无论放  
 
在哪个地方, 以下几点说明都是适合的。  
    1. main() 参数  
    在Turbo C2.0启动过程中, 传递main()函数三个参数: argc, argv和env。  
     * argc:  整数, 为传给main()的命令行参数个数。  
     * argv:  字符串数组。  
              在DOS 3.X 版本中, argv[0] 为程序运行的全路径名; 对DOS 3.0  
              以下的版本, argv[0]为空串("") 。  
              argv[1] 为在DOS命令行中执行程序名后的第一个字符串;  
              argv[2] 为执行程序名后的第二个字符串;  
              ...  
              argv[argc]为NULL。  
     *env:  安符串数组。env[] 的每一个元素都包含ENVVAR=value形式的字符  
串。其中ENVVAR为环境变量如PATH或87。value 为ENVVAR的对应值如C:\DOS, C:  
\TURBOC(对于PATH) 或YES(对于87)。  
    Turbo C2.0启动时总是把这三个参数传递给main()函数, 可以在用户程序中  
说明(或不说明)它们, 如果说明了部分(或全部)参数, 它们就成为main()子程序  
的局部变量。  
    请注意: 一旦想说明这些参数, 则必须按argc, argv, env 的顺序, 如以下  
的例子:  
     main()  
     main(int argc)  
     main(int argc, char *argv[])  
     main(int argc, char *argv[], char *env[])  
    其中第二种情况是合法的, 但不常见, 因为在程序中很少有只用argc, 而不  
用argv[]的情况。  
    以下提供一样例程序EXAMPLE.EXE,  演示如何在main()函数中使用三个参数:  
     /*program name EXAMPLE.EXE*/  
     #include <stdio.h>  
     #include <stdlib.h>  
     main(int argc, char *argv[], char *env[])  
     {  
          int i;  
          printf("These are the %d  command- line  arguments passed  to  
                  main:\n\n", argc);  
          for(i=0; i<=argc; i++)  
            printf("argv[%d]:%s\n", i, argv[i]);  
          printf("\nThe environment string(s)on this system are:\n\n");  
          for(i=0; env[i]!=NULL; i++)  
               printf(" env[%d]:%s\n", i, env[i]);  
     }  
    如果在DOS 提示符下, 按以下方式运行EXAMPLE.EXE:  
    C:\example first_argument "argument with blanks"  3  4  "last  but  
one" stop!  
    注意: 可以用双引号括起内含空格的参数, 如本例中的:   "  argument  
with blanks"和"Last but one")。  
    结果是这样的:  
     The value of argc is 7  
     These are the 7 command-linearguments passed to main:  
     argv[0]:C:\TURBO\EXAMPLE.EXE  
     argv[1]:first_argument  
     argv[2]:argument with blanks  
     argv[3]:3  
     argv[4]:4  
     argv[5]:last but one  
     argv[6]:stop!  
     argv[7]:(NULL)  
     The environment string(s) on this system are:  
     env[0]: COMSPEC=C:\COMMAND.COM  
     env[1]: PROMPT=$P$G            /*视具体设置而定*/  
     env[2]: PATH=C:\DOS;C:\TC      /*视具体设置而定*/  
   
     应该提醒的是: 传送main() 函数的命令行参数的最大长度为128 个字符 (包  
括参数间的空格),  这是由DOS 限制的。  
   

函数名: matherr  
功  能: 用户可修改的数学错误处理程序  
用  法: int matherr(struct exception *e);  
程序例:  

/* This is a user-defined matherr function that prevents  
   any error messages from being printed. */  

#include<math.h>  

int matherr(struct exception *a)  
{  
   return 1;  
}  
   
   
   

函数名: memccpy  
功  能: 从源source中拷贝n个字节到目标destin中  
用  法: void *memccpy(void *destin, void *source, unsigned char ch,  
       unsigned n);  
程序例:  

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

int main(void)  
{  
   char *src = "This is the source string";  
   char dest[50];  
   char *ptr;  

   ptr = memccpy(dest, src, 'c', strlen(src));  

   if (ptr)  
   {  
      *ptr = '\0';  
      printf("The character was found:  %s\n", dest);  
   }  
   else  
      printf("The character wasn't found\n");  
   return 0;  
}  
   
   

函数名: malloc  
功  能: 内存分配函数  
用  法: void *malloc(unsigned size);  
程序例:  

#include <stdio.h>  
#include <string.h>  
#include <alloc.h>  
#include <process.h>  

int main(void)  
{  
   char *str;  

   /* allocate memory for string */  
   /* This will generate an error when compiling */  
   /* with C++, use the new operator instead. */  
   if ((str = malloc(10)) == NULL)  
   {  
      printf("Not enough memory to allocate buffer\n");  
      exit(1);  /* terminate program if out of memory */  
   }  

   /* copy "Hello" into string */  
   strcpy(str, "Hello");  

   /* display string */  
   printf("String is %s\n", str);  

   /* free memory */  
   free(str);  

   return 0;  
}  
   
   
   

函数名: memchr  
功  能: 在数组的前n个字节中搜索字符  
用  法: void *memchr(void *s, char ch, unsigned n);  
程序例:  

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

int main(void)  
{  
   char str[17];  
   char *ptr;  

   strcpy(str, "This is a string");  
   ptr = memchr(str, 'r', strlen(str));  
   if (ptr)  
      printf("The character 'r' is at position: %d\n", ptr - str);  
   else  
      printf("The character was not found\n");  
   return 0;  
}  
   

函数名: memcpy  
功  能: 从源source中拷贝n个字节到目标destin中  
用  法: void *memcpy(void *destin, void *source, unsigned n);  
程序例:  

#include <stdio.h>  
#include <string.h>  
int main(void)  
{  
   char src[] = "******************************";  
   char dest[] = "abcdefghijlkmnopqrstuvwxyz0123456709";  
   char *ptr;  
   printf("destination before memcpy: %s\n", dest);  
   ptr = memcpy(dest, src, strlen(src));  
   if (ptr)  
      printf("destination after memcpy:  %s\n", dest);  
   else  
      printf("memcpy failed\n");  
   return 0;  
}  
   
   

函数名: memicmp  
功  能: 比较两个串s1和s2的前n个字节, 忽略大小写  
用  法: int memicmp(void *s1, void *s2, unsigned n);  
程序例:  

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

int main(void)  
{  
   char *buf1 = "ABCDE123";  
   char *buf2 = "abcde456";  
   int stat;  
   stat = memicmp(buf1, buf2, 5);  
   printf("The strings to position 5 are ");  
   if (stat)  
      printf("not ");  
   printf("the same\n");  
   return 0;  
}  
   
   

函数名: memmove  
功  能: 移动一块字节  
用  法: void *memmove(void *destin, void *source, unsigned n);  
程序例:  

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

int main(void)  
{  
  char *dest = "abcdefghijklmnopqrstuvwxyz0123456789";  
  char *src = "******************************";  
  printf("destination prior to memmove: %s\n", dest);  
  memmove(dest, src, 26);  
  printf("destination after memmove:    %s\n", dest);  
  return 0;  
}  
   
   
   

函数名: memset  
功  能: 设置s中的所有字节为ch, s数组的大小由n给定  
用  法: void *memset(void *s, char ch, unsigned n);  
程序例:  

#include <string.h>  
#include <stdio.h>  
#include <mem.h>  

int main(void)  
{  
   char buffer[] = "Hello world\n";  

   printf("Buffer before memset: %s\n", buffer);  
   memset(buffer, '*', strlen(buffer) - 1);  
   printf("Buffer after memset:  %s\n", buffer);  
   return 0;  
}  
   
   

函数名: mkdir  
功  能: 建立一个目录  
用  法: int mkdir(char *pathname);  
程序例:  

#include <stdio.h>  
#include <conio.h>  
#include <process.h>  
#include <dir.h>  

int main(void)  
{  
  int status;  

   clrscr();  
   status = mkdir("asdfjklm");  
   (!status) ? (printf("Directory created\n")) :  
               (printf("Unable to create directory\n"));  

   getch();  
   system("dir");  
   getch();  

   status = rmdir("asdfjklm");  
   (!status) ? (printf("Directory deleted\n")) :  
  (perror("Unable to delete directory"));  

   return 0;  
}  
   
   
   

函数名: mktemp  
功  能: 建立唯一的文件名  
用  法: char *mktemp(char *template);  
程序例:  

#include <dir.h>  
#include <stdio.h>  

int main(void)  
{  
   /* fname defines the template for the  
     temporary file.  */  

   char *fname = "TXXXXXX", *ptr;  

   ptr = mktemp(fname);  
   printf("%s\n",ptr);  
   return 0;  
}  
   
   

函数名: MK_FP  
功  能: 设置一个远指针  
用  法: void far *MK_FP(unsigned seg, unsigned off);  
程序例:  

#include <dos.h>  
#include <graphics.h>  

int main(void)  
{  
   int gd, gm, i;  
   unsigned int far *screen;  

   detectgraph(&gd, &gm);  
   if (gd == HERCMONO)  
       screen = MK_FP(0xB000, 0);  
   else  
       screen = MK_FP(0xB800, 0);  
   for (i=0; i<26; i++)  
      screen[i] = 0x0700 + ('a' + i);  
   return 0;  
}  
   
   

函数名: modf  
功  能: 把数分为指数和尾数  
用  法: double modf(double value, double *iptr);  
程序例:  

#include <math.h>  
#include <stdio.h>  

int main(void)  
{  
   double fraction, integer;  
   double number = 100000.567;  

   fraction = modf(number, &integer);  
   printf("The whole and fractional parts of %lf are %lf and %lf\n",  
          number, integer, fraction);  
   return 0;  
}  
   
   

函数名: movedata  
功  能: 拷贝字节  
用  法: void movedata(int segsrc, int offsrc, int segdest,  
  int offdest, unsigned numbytes);  
程序例:  

#include <mem.h>  

#define MONO_BASE 0xB000  

/* saves the contents of the monochrome screen in buffer */  
void save_mono_screen(char near *buffer)  
{  
   movedata(MONO_BASE, 0, _DS, (unsigned)buffer, 80*25*2);  
}  

int main(void)  
{  
   char buf[80*25*2];  
   save_mono_screen(buf);  
}  
   
   

函数名: moverel  
功  能: 将当前位置(CP)移动一相对距离  
用  法: void far moverel(int dx, int dy);  
程序例:  

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

int main(void)  
{  
   /* request auto detection */  
   int gdriver = DETECT, gmode, errorcode;  
   char msg[80];  

   /* initialize graphics and local variables */  
   initgraph(&gdriver, &gmode, "");  

   /* read result of initialization */  
   errorcode = graphresult();  
   if (errorcode != grOk)  /* an error occurred */  
   {  
      printf("Graphics error: %s\n", grapherrormsg(errorcode));  
      printf("Press any key to halt:");  
      getch();  
      exit(1); /* terminate with an error code */  
   }  

   /* move the C.P. to location (20, 30) */  
   moveto(20, 30);  

   /* plot a pixel at the C.P. */  
   putpixel(getx(), gety(), getmaxcolor());  

   /* create and output a message at (20, 30) */  
   sprintf(msg, " (%d, %d)", getx(), gety());  
   outtextxy(20, 30, msg);  

   /* move to a point a relative distance */  
   /* away from the current value of C.P. */  
   moverel(100, 100);  

   /* plot a pixel at the C.P. */  
   putpixel(getx(), gety(), getmaxcolor());  

   /* create and output a message at C.P. */  
   sprintf(msg, " (%d, %d)", getx(), gety());  
   outtext(msg);  

   /* clean up */  
   getch();  
   closegraph();  
   return 0;  
}  
   
   

函数名: movetext  
功  能: 将屏幕文本从一个矩形区域拷贝到另一个矩形区域  
用  法: int movetext(int left, int top, int right, int bottom,  
  int newleft, int newtop);  
程序例:  
#include <conio.h>  
#include <string.h>  

int main(void)  
{  
   char *str = "This is a test string";  

   clrscr();  
   cputs(str);  
   getch();  

   movetext(1, 1, strlen(str), 2, 10, 10);  
   getch();  

   return 0;  
}  
   
   

函数名: moveto  
功  能: 将CP移到(x, y)  
用  法: void far moveto(int x, int y);  
程序例:  

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

int main(void)  
{  
   /* request auto detection */  
   int gdriver = DETECT, gmode, errorcode;  
   char msg[80];  

   /* initialize graphics and local variables */  
   initgraph(&gdriver, &gmode, "");  

   /* read result of initialization */  
   errorcode = graphresult();  
   if (errorcode != grOk)  /* an error occurred */  
   {  
      printf("Graphics error: %s\n", grapherrormsg(errorcode));  
      printf("Press any key to halt:");  
      getch();  
      exit(1); /* terminate with an error code */  
   }  

   /* move the C.P. to location (20, 30) */  
   moveto(20, 30);  

   /* plot a pixel at the C.P. */  
   putpixel(getx(), gety(), getmaxcolor());  

   /* create and output a message at (20, 30) */  
   sprintf(msg, " (%d, %d)", getx(), gety());  
   outtextxy(20, 30, msg);  

   /* move to (100, 100) */  
   moveto(100, 100);  

   /* plot a pixel at the C.P. */  
   putpixel(getx(), gety(), getmaxcolor());  

   /* create and output a message at C.P. */  
   sprintf(msg, " (%d, %d)", getx(), gety());  
   outtext(msg);  

   /* clean up */  
   getch();  
   closegraph();  
   return 0;  
}  
   
   

函数名: movemem  
功  能: 移动一块字节  
用  法: void movemem(void *source, void *destin, unsigned len);  
程序例:  

#include <mem.h>  
#include <alloc.h>  
#include <stdio.h>  
#include <string.h>  

int main(void)  
{  
   char *source = "Borland International";  
   char *destination;  
   int length;  

   length = strlen(source);  
   destination = malloc(length + 1);  
   movmem(source,destination,length);  
   printf("%s\n",destination);  

   return 0;  
}  
   
   

函数名: normvideo  
功  能: 选择正常亮度字符  
用  法: void normvideo(void);  
程序例:  

#include <conio.h>  

int main(void)  
{  
   normvideo();  
   cprintf("NORMAL Intensity Text\r\n");  
   return 0;  
}  
   
   

函数名: nosound  
功  能: 关闭PC扬声器  
用  法: void nosound(void);  
程序例:  

/* Emits a 7-Hz tone for 10 seconds.  

     True story: 7 Hz is the resonant frequency of a chicken's skull cavity.  
     This was determined empirically in Australia, where a new factory  
     generating 7-Hz tones was located too close to a chicken ranch:  
     When the factory started up, all the chickens died.  

     Your PC may not be able to emit a 7-Hz tone.  
*/  

int main(void)  
{  
   sound(7);  
   delay(10000);  
   nosound();  
}