wdg_022f.txt

c编程宝典,详细介绍有关c的资料

函数名: fabs 
功  能: 返回浮点数的绝对值 
用  法: double fabs(double x); 
程序例: 

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

int main(void) 
{ 
   float  number = -1234.0; 

   printf("number: %f  absolute value: %f\n", 
   number, fabs(number)); 
   return 0; 
} 
  
  
  

函数名: farcalloc 
功  能: 从远堆栈中申请空间 
用  法: void far *farcalloc(unsigned long units, unsigned ling unitsz); 
程序例: 
#include <stdio.h> 
#include <alloc.h> 
#include <string.h> 
#include <dos.h> 

int main(void) 
{ 
   char far *fptr; 
   char *str = "Hello"; 

   /* allocate memory for the far pointer */ 
   fptr = farcalloc(10, sizeof(char)); 

   /* copy "Hello" into allocated memory */ 
   /* 
      Note: movedata is used because you 
      might be in a small data model, in 
      which case a normal string copy routine 
      can not be used since it assumes the 
      pointer size is near. 
   */ 
   movedata(FP_SEG(str), FP_OFF(str), 
     FP_SEG(fptr), FP_OFF(fptr), 
            strlen(str)); 

   /* display string (note the F modifier) */ 
   printf("Far string is: %Fs\n", fptr); 

   /* free the memory */ 
   farfree(fptr); 

   return 0; 
} 
  
  
  

函数名: farcoreleft 
功  能: 返回远堆中未作用存储区大小 
用  法: long farcoreleft(void); 
程序例: 

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

int main(void) 
{ 
   printf("The difference between the\ 
    highest allocated block in the\ 
           far\n"); 
   printf("heap and the top of the far heap\ 
           is: %lu bytes\n", farcoreleft()); 

   return 0; 
} 
  
  
  

函数名: farfree 
功  能: 从远堆中释放一块 
用  法: void farfree(void); 
程序例: 

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

int main(void) 
{ 
   char far *fptr; 
   char *str = "Hello"; 

   /* allocate memory for the far pointer */ 
   fptr = farcalloc(10, sizeof(char)); 

   /* copy "Hello" into allocated memory */ 
   /* 
      Note: movedata is used because you might be in a small data model, 
      in which case a normal string copy routine can't be used since it 
      assumes the pointer size is near. 
   */ 
   movedata(FP_SEG(str), FP_OFF(str), 
            FP_SEG(fptr), FP_OFF(fptr), 
            strlen(str)); 

   /* display string (note the F modifier) */ 
   printf("Far string is: %Fs\n", fptr); 

   /* free the memory */ 
   farfree(fptr); 

   return 0; 
} 
  
  
  

函数名: farmalloc 
功  能: 从远堆中分配存储块 
用  法: void far *farmalloc(unsigned long size); 
程序例: 

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

int main(void) 
{ 
   char far *fptr; 
   char *str = "Hello"; 

   /* allocate memory for the far pointer */ 
   fptr = farmalloc(10); 

   /* copy "Hello" into allocated memory */ 
   /* 
      Note: movedata is used because we might 
      be in a small data model, in which case 
      a normal string copy routine can not be 
      used since it assumes the pointer size 
      is near. 
   */ 
   movedata(FP_SEG(str), FP_OFF(str), 
     FP_SEG(fptr), FP_OFF(fptr), 
     strlen(str)); 

   /* display string (note the F modifier) */ 
   printf("Far string is: %Fs\n", fptr); 

   /* free the memory */ 
   farfree(fptr); 

   return 0; 
} 
  
  
  

函数名: farrealloc 
功  能: 调整远堆中的分配块 
用  法: void far *farrealloc(void far *block, unsigned long newsize); 
程序例: 

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

int main(void) 
{ 
   char far *fptr; 

   fptr = farmalloc(10); 
   printf("First address: %Fp\n", fptr); 
   fptr = farrealloc(fptr,20); 
   printf("New address  : %Fp\n", fptr); 
   farfree(fptr); 
   return 0; 
} 
  
  

函数名: fclose 
功  能: 关闭一个流 
用  法: int fclose(FILE *stream); 
程序例: 

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

int main(void) 
{ 
   FILE *fp; 
   char buf[11] = "0123456789"; 

   /* create a file containing 10 bytes */ 
   fp = fopen("DUMMY.FIL", "w"); 
   fwrite(&buf, strlen(buf), 1, fp); 

   /* close the file */ 
   fclose(fp); 
   return 0; 
} 
  
  
  

函数名: fcloseall 
功  能: 关闭打开流 
用  法: int fcloseall(void); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   int streams_closed; 

   /* open two streams */ 
   fopen("DUMMY.ONE", "w"); 
   fopen("DUMMY.TWO", "w"); 

   /* close the open streams */ 
   streams_closed = fcloseall(); 

   if (streams_closed == EOF) 
      /* issue an error message */ 
      perror("Error"); 
   else 
      /* print result of fcloseall() function */ 
      printf("%d streams were closed.\n", streams_closed); 

   return 0; 
} 
  
  

函数名: fcvt 
功  能: 把一个浮点数转换为字符串 
用  法: char *fcvt(double value, int ndigit, int *decpt, int *sign); 
程序例: 

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

int main(void) 
{ 
   char *string; 
   double value; 
   int dec, sign; 
   int ndig = 10; 

   clrscr(); 
   value = 9.876; 
   string = ecvt(value, ndig, &dec, &sign); 
   printf("string = %s      dec = %d \ 
          sign = %d\n", string, dec, sign); 

   value = -123.45; 
   ndig= 15; 
   string = ecvt(value,ndig,&dec,&sign); 
   printf("string = %s dec = %d sign = %d\n", 
          string, dec, sign); 
  

   value = 0.6789e5; /* scientific 
                        notation */ 
   ndig = 5; 
   string = ecvt(value,ndig,&dec,&sign); 
   printf("string = %s           dec = %d\ 
          sign = %d\n", string, dec, sign); 

   return 0; 
} 
  
  
  

函数名: fdopen 
功  能: 把流与一个文件句柄相接 
用  法: FILE *fdopen(int handle, char *type); 
程序例: 

#include <sys\stat.h> 
#include <stdio.h> 
#include <fcntl.h> 
#include <io.h> 

int main(void) 
{ 
   int handle; 
   FILE *stream; 

   /* open a file */ 
   handle = open("DUMMY.FIL", O_CREAT, 
    S_IREAD | S_IWRITE); 

   /* now turn the handle into a stream */ 
   stream = fdopen(handle, "w"); 

   if (stream == NULL) 
      printf("fdopen failed\n"); 
   else 
   { 
      fprintf(stream, "Hello world\n"); 
      fclose(stream); 
   } 
   return 0; 
} 
  
  

函数名: feof 
功  能: 检测流上的文件结束符 
用  法: int feof(FILE *stream); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   FILE *stream; 

   /* open a file for reading */ 
   stream = fopen("DUMMY.FIL", "r"); 

   /* read a character from the file */ 
   fgetc(stream); 

   /* check for EOF */ 
   if (feof(stream)) 
      printf("We have reached end-of-file\n"); 

   /* close the file */ 
   fclose(stream); 
   return 0; 
} 
  
  

函数名: ferror 
功  能: 检测流上的错误 
用  法: int ferror(FILE *stream); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   FILE *stream; 

   /* open a file for writing */ 
   stream = fopen("DUMMY.FIL", "w"); 

   /* force an error condition by attempting to read */ 
   (void) getc(stream); 

   if (ferror(stream))  /* test for an error on the stream */ 
   { 
      /* display an error message */ 
      printf("Error reading from DUMMY.FIL\n"); 

      /* reset the error and EOF indicators */ 
      clearerr(stream); 
   } 

   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: fflush 
功  能: 清除一个流 
用  法: int fflush(FILE *stream); 
程序例: 

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

void flush(FILE *stream); 

int main(void) 
{ 
   FILE *stream; 
   char msg[] = "This is a test"; 

   /* create a file */ 
   stream = fopen("DUMMY.FIL", "w"); 

   /* write some data to the file */ 
   fwrite(msg, strlen(msg), 1, stream); 

   clrscr(); 
   printf("Press any key to flush\ 
   DUMMY.FIL:"); 
   getch(); 

   /* flush the data to DUMMY.FIL without\ 
      closing it */ 
   flush(stream); 

   printf("\nFile was flushed, Press any key\ 
   to quit:"); 
   getch(); 
   return 0; 
} 

void flush(FILE *stream) 
{ 
     int duphandle; 

     /* flush the stream's internal buffer */ 
     fflush(stream); 

     /* make a duplicate file handle */ 
     duphandle = dup(fileno(stream)); 

     /* close the duplicate handle to flush\ 
        the DOS buffer */ 
     close(duphandle); 
} 
  
  
  

函数名: fgetc 
功  能: 从流中读取字符 
用  法: int fgetc(FILE *stream); 
程序例: 

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

int main(void) 
{ 
   FILE *stream; 
   char string[] = "This is a test"; 
   char ch; 

   /* open a file for update */ 
   stream = fopen("DUMMY.FIL", "w+"); 

   /* write a string into the file */ 
   fwrite(string, strlen(string), 1, stream); 

   /* seek to the beginning of the file */ 
   fseek(stream, 0, SEEK_SET); 

   do 
   { 
      /* read a char from the file */ 
      ch = fgetc(stream); 

      /* display the character */ 
      putch(ch); 
   } while (ch != EOF); 

   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: fgetchar 
功  能: 从流中读取字符 
用  法: int fgetchar(void); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   char ch; 

   /* prompt the user for input */ 
   printf("Enter a character followed by \ 
   <Enter>: "); 

   /* read the character from stdin */ 
   ch = fgetchar(); 

   /* display what was read */ 
   printf("The character read is: '%c'\n", 
          ch); 
   return 0; 
} 
  
  
  

函数名: fgetpos 
功  能: 取得当前文件的句柄 
用  法: int fgetpos(FILE *stream); 
程序例: 

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

int main(void) 
{ 
   FILE *stream; 
   char string[] = "This is a test"; 
   fpos_t filepos; 

   /* open a file for update */ 
   stream = fopen("DUMMY.FIL", "w+"); 

   /* write a string into the file */ 
   fwrite(string, strlen(string), 1, stream); 

   /* report the file pointer position */ 
   fgetpos(stream, &filepos); 
   printf("The file pointer is at byte\ 
          %ld\n", filepos); 

   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: fgets 
功  能: 从流中读取一字符串 
用  法: char *fgets(char *string, int n, FILE *stream); 
程序例: 

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

int main(void) 
{ 
   FILE *stream; 
   char string[] = "This is a test"; 
   char msg[20]; 

   /* open a file for update */ 
   stream = fopen("DUMMY.FIL", "w+"); 

   /* write a string into the file */ 
   fwrite(string, strlen(string), 1, stream); 

   /* seek to the start of the file */ 
   fseek(stream, 0, SEEK_SET); 

   /* read a string from the file */ 
   fgets(msg, strlen(string)+1, stream); 

   /* display the string */ 
   printf("%s", msg); 

   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: filelength 
功  能: 取文件长度字节数 
用  法: long filelength(int handle); 
程序例: 

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

int main(void) 
{ 
   int handle; 
   char buf[11] = "0123456789"; 

   /* create a file containing 10 bytes */ 
   handle = open("DUMMY.FIL", O_CREAT); 
   write(handle, buf, strlen(buf)); 

   /* display the size of the file */ 
   printf("file length in bytes: %ld\n", 
   filelength(handle)); 

   /* close the file */ 
   close(handle); 
   return 0; 
} 
  
  

函数名: fillellipse 
功  能: 画出并填充一椭圆 
用  法: void far fillellipse(int x, int y, int xradius, int yradius); 
程序例: 

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

int main(void) 
{ 
   int gdriver = DETECT, gmode; 
   int xcenter, ycenter, i; 

   initgraph(&gdriver,&gmode,""); 
   xcenter = getmaxx() / 2; 
   ycenter = getmaxy() / 2; 

   for (i=0; i<13; i++) 
   { 
      setfillstyle(i,WHITE); 
      fillellipse(xcenter,ycenter,100,50); 
      getch(); 
   } 

   closegraph(); 
   return 0; 
} 
  
  
  

函数名: fillpoly 
功  能: 画并填充一个多边形 
用  法: void far fillpoly(int numpoints, int far *polypoints); 
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; 
   int i, maxx, maxy; 

   /* our polygon array */ 
   int poly[8]; 

   /* initialize graphics, 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 */ 
   } 

   maxx = getmaxx(); 
   maxy = getmaxy(); 

   poly[0] = 20;        /* 1st vertext */ 
   poly[1] = maxy / 2; 

   poly[2] = maxx - 20; /* 2nd */ 
   poly[3] = 20; 

   poly[4] = maxx - 50; /* 3rd */ 
   poly[5] = maxy - 20; 

   /* 
      4th vertex. fillpoly automatically 
      closes the polygon. 
   */ 
   poly[6] = maxx / 2; 
   poly[7] = maxy / 2; 

   /* loop through the fill patterns */ 
   for (i=EMPTY_FILL; i<USER_FILL; i++) 
   { 
      /* set fill pattern */ 
      setfillstyle(i, getmaxcolor()); 

      /* draw a filled polygon */ 
      fillpoly(4, poly); 

      getch(); 
   } 

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

函数名: findfirst, findnext 
功  能: 搜索磁盘目录; 取得下一个匹配的findfirst模式的文件 
用  法: int findfirst(char *pathname, struct ffblk *ffblk, int attrib); 
 int findnext(struct ffblk *ffblk); 
程序例: 

/* findnext example */ 

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

int main(void) 
{ 
   struct ffblk ffblk; 
   int done; 
   printf("Directory listing of *.*\n"); 
   done = findfirst("*.*",&ffblk,0); 
   while (!done) 
   { 
      printf("  %s\n", ffblk.ff_name); 
      done = findnext(&ffblk); 
   } 

   return 0; 
}