F开头的函数

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");  &