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; 
} 
  
  
  

函数名: floodfill

功 能: 填充一个有界区域

用 法: void far floodfill(int x, int y, int border);

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 maxx, maxy; 
   /* 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(); 
   /* select drawing color */ 
   setcolor(getmaxcolor()); 
   /* select fill color */ 
   setfillstyle(SOLID_FILL, getmaxcolor()); 
   /* draw a border around the screen */ 
   rectangle(0, 0, maxx, maxy); 
   /* draw some circles */ 
   circle(maxx / 3, maxy /2, 50); 
   circle(maxx / 2, 20, 100); 
   circle(maxx-20, maxy-50, 75); 
   circle(20, maxy-20, 25); 
   /* wait for a key */ 
   getch(); 
   /* fill in bounded region */ 
   floodfill(2, 2, getmaxcolor()); 
   /* clean up */ 
   getch(); 
   closegraph(); 
   return 0; 
} 
  
  
  

函数名: floor

功 能: 向下舍入

用 法: double floor(double x);

程序例:

#include <stdio.h> 
#include <math.h> 
int main(void) 
{ 
   double number = 123.54; 
   double down, up; 
   down = floor(number); 
   up = ceil(number); 
   printf("original number     %10.2lf\n", 
          number); 
   printf("number rounded down %10.2lf\n", 
          down); 
   printf("number rounded up   %10.2lf\n", 
          up); 
   return 0; 
} 
  
  
  

函数名: flushall

功 能: 清除所有缓冲区

用 法: int flushall(void);

程序例:

#include <stdio.h> 
int main(void) 
{ 
   FILE *stream; 
   /* create a file */ 
   stream = fopen("DUMMY.FIL", "w"); 
   /* flush all open streams */ 
   printf("%d streams were flushed.\n", 
   flushall()); 
   /* close the file */ 
   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: fmod

功 能: 计算x对y的模, 即x/y的余数

用 法: double fmod(double x, double y);

程序例:

#include <stdio.h> 
#include <math.h> 
int main(void) 
{ 
   double x = 5.0, y = 2.0; 
   double result; 
   result = fmod(x,y); 
   printf("The remainder of (%lf / %lf) is \ 
          %lf\n", x, y, result); 
   return 0; 
} 
  
  
  

函数名: fnmerge

功 能: 建立新文件名

用 法: void fnerge(char *path, char *drive, char *dir);

程序例:

#include <string.h> 
#include <stdio.h> 
#include <dir.h> 
  
int main(void) 
{ 
    char s[MAXPATH]; 
    char drive[MAXDRIVE]; 
    char dir[MAXDIR]; 
    char file[MAXFILE]; 
    char ext[MAXEXT]; 
    getcwd(s,MAXPATH);              /* get the current working directory */ 
    strcat(s,"\\");                  /* append on a trailing \ character */ 
    fnsplit(s,drive,dir,file,ext); /* split the string to separate elems */ 
    strcpy(file,"DATA"); 
    strcpy(ext,".TXT"); 
    fnmerge(s,drive,dir,file,ext);   /* merge everything into one string */ 
    puts(s);                                 /* display resulting string */ 
    return 0; 
} 
  
  
  

函数名: fopen

功 能: 打开一个流

用 法: FILE *fopen(char *filename, char *type);

程序例:

#include <stdlib.h> 
#include <stdio.h> 
#include <dir.h> 
int main(void) 
{ 
    char *s; 
    char drive[MAXDRIVE]; 
    char dir[MAXDIR]; 
    char file[MAXFILE]; 
    char ext[MAXEXT]; 
    int flags; 
    s=getenv("COMSPEC"); /* get the comspec environment parameter */ 
    flags=fnsplit(s,drive,dir,file,ext); 
    printf("Command processor info:\n"); 
    if(flags & DRIVE) 
       printf("\tdrive: %s\n",drive); 
    if(flags & DIRECTORY) 
       printf("\tdirectory: %s\n",dir); 
    if(flags & FILENAME) 
       printf("\tfile: %s\n",file); 
    if(flags & EXTENSION) 
       printf("\textension: %s\n",ext); 
    return 0; 
} 
  

函数名: fprintf

功 能: 传送格式化输出到一个流中

用 法: int fprintf(FILE *stream, char *format[, argument,...]);

程序例:

/* Program to create backup of the 
   AUTOEXEC.BAT file */ 
#include <stdio.h> 
int main(void) 
{ 
   FILE *in, *out; 
   if ((in = fopen("\\AUTOEXEC.BAT", "rt")) 
       == NULL) 
   { 
      fprintf(stderr, "Cannot open input \ 
       file.\n"); 
      return 1; 
   } 
   if ((out = fopen("\\AUTOEXEC.BAK", "wt")) 
       == NULL) 
   { 
      fprintf(stderr, "Cannot open output \ 
       file.\n"); 
      return 1; 
   } 
   while (!feof(in)) 
      fputc(fgetc(in), out); 
   fclose(in); 
   fclose(out); 
   return 0; 
} 
  
  
  

函数名: FP_OFF

功 能: 获取远地址偏移量

用 法: unsigned FP_OFF(void far *farptr);

程序例:

/* FP_OFF */ 
#include <dos.h> 
#include <stdio.h> 
int main(void) 
{ 
   char *str = "fpoff.c"; 
   printf("The offset of this file in memory\ 
          is: %Fp\n", FP_OFF(str)); 
   return 0; 
} 
  
  

函数名: FP_SEG

功 能: 获取远地址段值

用 法: unsigned FP_SEG(void far *farptr);

程序例:

/* FP_SEG */ 
#include <dos.h> 
#include <stdio.h> 
int main(void) 
{ 
   char *filename = "fpseg.c"; 
   printf("The offset of this file in memory\ 
   is: %Fp\n", FP_SEG(filename)); 
   return(0); 
} 
  
  
  

函数名: fputc

功 能: 送一个字符到一个流中

用 法: int fputc(int ch, FILE *stream);

程序例:

#include <stdio.h> 
int main(void) 
{ 
   char msg[] = "Hello world"; 
   int i = 0; 
   while (msg[i]) 
   { 
      fputc(msg[i], stdout); 
      i++; 
   } 
   return 0; 
} 
  
  
  

函数名: fputchar

功 能: 送一个字符到标准输出流(stdout)中

用 法: int fputchar(char ch);

程序例:

#include <stdio.h> 
int main(void) 
{ 
   char msg[] = "This is a test"; 
   int i = 0; 
   while (msg[i]) 
   { 
      fputchar(msg[i]); 
      i++; 
   } 
   return 0; 
} 
  
  
  

函数名: fputs

功 能: 送一个字符到一个流中

用 法: int fputs(char *string, FILE *stream);

程序例:

#include <stdio.h> 
int main(void) 
{ 
   /* write a string to standard output */ 
   fputs("Hello world\n", stdout); 
   return 0; 
} 
  
  
  

函数名: fread

功 能: 从一个流中读数据

用 法: int fread(void *ptr, int size, int nitems, FILE *stream);

程序例:

#include <string.h> 
#include <stdio.h> 
int main(void) 
{ 
   FILE *stream; 
   char msg[] = "this is a test"; 
   char buf[20]; 
   if ((stream = fopen("DUMMY.FIL", "w+")) 
       == NULL) 
   { 
      fprintf(stderr, 
              "Cannot open output file.\n"); 
      return 1; 
   } 
   /* write some data to the file */ 
   fwrite(msg, strlen(msg)+1, 1, stream); 
   /* seek to the beginning of the file */ 
   fseek(stream, SEEK_SET, 0); 
   /* read the data and display it */ 
   fread(buf, strlen(msg)+1, 1, stream); 
   printf("%s\n", buf); 
   fclose(stream); 
   return 0; 
} 
  
  

函数名: free

功 能: 释放已分配的块

用 法: void free(void *ptr);

程序例:

#include <string.h> 
#include <stdio.h> 
#include <alloc.h> 
int main(void) 
{ 
   char *str; 
   /* allocate memory for string */ 
   str = malloc(10); 
   /* copy "Hello" to string */ 
   strcpy(str, "Hello"); 
   /* display string */ 
   printf("String is %s\n", str); 
   /* free memory */ 
   free(str); 
   return 0; 
} 
  

函数名: freemem

功 能: 释放先前分配的DOS内存块

用 法: int freemem(unsigned seg);

程序例:

#include <dos.h> 
#include <alloc.h> 
#include <stdio.h> 
int main(void) 
{ 
   unsigned int size, segp; 
   int stat; 
   size = 64; /* (64 x 16) = 1024 bytes */ 
   stat = allocmem(size, &segp); 
   if (stat < 0) 
      printf("Allocated memory at segment:\ 
      %x\n", segp); 
   else 
      printf("Failed: maximum number of\ 
      paragraphs available is %u\n", 
      stat); 
   freemem(segp); 
   return 0; 
} 
  
  

函数名: freopen

功 能: 替换一个流

用 法: FILE *freopen(char *filename, char *type, FILE *stream);

程序例:

#include <stdio.h> 
int main(void) 
{ 
   /* redirect standard output to a file */ 
   if (freopen("OUTPUT.FIL", "w", stdout) 
       == NULL) 
      fprintf(stderr, "error redirecting\ 
              stdout\n"); 
   /* this output will go to a file */ 
   printf("This will go into a file."); 
   /* close the standard output stream */ 
   fclose(stdout); 
   return 0; 
} 
  
  
  

函数名: frexp

功 能: 把一个双精度数分解为尾数的指数

用 法: double frexp(double value, int *eptr);

程序例:

#include <math.h> 
#include <stdio.h> 
int main(void) 
{ 
   double mantissa, number; 
   int exponent; 
   number = 8.0; 
   mantissa = frexp(number, &exponent); 
   printf("The number %lf is ", number); 
   printf("%lf times two to the ", mantissa); 
   printf("power of %d\n", exponent); 
   return 0; 
} 
  
  

函数名: fscanf

功 能: 从一个流中执行格式化输入

用 法: int fscanf(FILE *stream, char *format[,argument...]);

程序例:

#include <stdlib.h> 
#include <stdio.h> 
int main(void) 
{ 
   int i; 
   printf("Input an integer: "); 
   /* read an integer from the 
      standard input stream */ 
   if (fscanf(stdin, "%d", &i)) 
      printf("The integer read was: %i\n", 
             i); 
   else 
   { 
      fprintf(stderr, "Error reading an \ 
              integer from stdin.\n"); 
      exit(1); 
   } 
   return 0; 
} 
  
  
  

函数名: fseek

功 能: 重定位流上的文件指针

用 法: int fseek(FILE *stream, long offset, int fromwhere);

程序例:

#include <stdio.h> 
long filesize(FILE *stream); 
int main(void) 
{ 
   FILE *stream; 
   stream = fopen("MYFILE.TXT", "w+"); 
   fprintf(stream, "This is a test"); 
   printf("Filesize of MYFILE.TXT is %ld bytes\n", filesize(stream)); 
   fclose(stream); 
   return 0; 
} 
long filesize(FILE *stream) 
{ 
   long curpos, length; 
   curpos = ftell(stream); 
   fseek(stream, 0L, SEEK_END); 
   length = ftell(stream); 
   fseek(stream, curpos, SEEK_SET); 
   return length; 
} 
  
  
  
  
  

函数名: fsetpos

功 能: 定位流上的文件指针

用 法: int fsetpos(FILE *stream, const fpos_t *pos);

程序例:

#include <stdlib.h> 
#include <stdio.h> 
void showpos(FILE *stream); 
int main(void) 
{ 
   FILE *stream; 
   fpos_t filepos; 
   /* open a file for update */ 
   stream = fopen("DUMMY.FIL", "w+"); 
   /* save the file pointer position */ 
   fgetpos(stream, &filepos); 
   /* write some data to the file */ 
   fprintf(stream, "This is a test"); 
   /* show the current file position */ 
   showpos(stream); 
   /* set a new file position, display it */ 
   if (fsetpos(stream, &filepos) == 0) 
     showpos(stream); 
   else 
   { 
      fprintf(stderr, "Error setting file \ 
       pointer.\n"); 
      exit(1); 
   } 
   /* close the file */ 
   fclose(stream); 
   return 0; 
} 
void showpos(FILE *stream) 
{ 
   fpos_t pos; 
   /* display the current file pointer 
      position of a stream */ 
   fgetpos(stream, &pos); 
   printf("File position: %ld\n", pos); 
} 
  

函数名: fstat

功 能: 获取打开文件信息

用 法: int fstat(char *handle, struct stat *buff);

程序例:

#include <sys\stat.h> 
#include <stdio.h> 
#include <time.h> 
int main(void) 
{ 
   struct stat statbuf; 
   FILE *stream; 
   /* open a file for update */ 
   if ((stream = fopen("DUMMY.FIL", "w+")) 
       == NULL) 
   { 
      fprintf(stderr, "Cannot open output \ 
              file.\n"); 
      return(1); 
   } 
   fprintf(stream, "This is a test"); 
   fflush(stream); 
   /* get information about the file */ 
   fstat(fileno(stream), &statbuf); 
   fclose(stream); 
   /* display the information returned */ 
   if (statbuf.st_mode & S_IFCHR) 
      printf("Handle refers to a device.\n"); 
   if (statbuf.st_mode & S_IFREG) 
      printf("Handle refers to an ordinary \ 
             file.\n"); 
   if (statbuf.st_mode & S_IREAD) 
      printf("User has read permission on \ 
             file.\n"); 
   if (statbuf.st_mode & S_IWRITE) 
      printf("User has write permission on \ 
              file.\n"); 
   printf("Drive letter of file: %c\n", 
   ‘A‘+statbuf.st_dev); 
   printf("Size of file in bytes: %ld\n", 
   statbuf.st_size); 
   printf("Time file last opened: %s\n", 
   ctime(&statbuf.st_ctime)); 
   return 0; 
} 
  
  
  

函数名: ftell

功 能: 返回当前文件指针

用 法: long ftell(FILE *stream);

程序例:

#include <stdio.h> 
int main(void) 
{ 
   FILE *stream; 
   stream = fopen("MYFILE.TXT", "w+"); 
   fprintf(stream, "This is a test"); 
   printf("The file pointer is at byte \ 
          %ld\n", ftell(stream)); 
   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: fwrite

功 能: 写内容到流中

用 法: int fwrite(void *ptr, int size, int nitems, FILE *stream);

程序例:

#include <stdio.h> 
struct mystruct 
{ 
  int i; 
  char ch; 
}; 
int main(void) 
{ 
   FILE *stream; 
   struct mystruct s; 
   if ((stream = fopen("TEST.$$$", "wb")) == NULL) /* open file TEST.$$$ */ 
   { 
      fprintf(stderr, "Cannot open output file.\n"); 
      return 1; 
   } 
   s.i = 0; 
   s.ch = ‘A‘; 
   fwrite(&s, sizeof(s), 1, stream); /* write struct s to file */ 
   fclose(stream); /* close file */ 
   return 0; 
}