函數名: raise  
功  能: 向正在執行的程序發送一個信號  
用  法: int raise(int sig);  
程序例:  

#include <signal.h>  

int main(void)  
{  
   int a, b;  

   a = 10;  
   b = 0;  
   if (b == 0)  
   /* preempt divide by zero error */  
      raise(SIGFPE);  
   a = a / b;  
   return 0;  
}  
   
   

函數名: rand  
功  能: 隨機數發生器  
用  法: void rand(void);  
程序例:  

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

int main(void)  
{  
   int i;  

   printf("Ten random numbers from 0 to 99\n\n");  
   for(i=0; i<10; i++)  
      printf("%d\n", rand() % 100);  
   return 0;  
}  
   
   

函數名: randbrd  
功  能: 隨機塊讀  
用  法: int randbrd(struct fcb *fcbptr, int reccnt);  
程序例:  

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

int main(void)  
{  
   char far *save_dta;  
   char line[80], buffer[256];  
   struct fcb blk;  
   int i, result;  

   /* get user input file name for dta */  
   printf("Enter drive and file name (no path - i.e. a:file.dat)\n");  
   gets(line);  

   /* put file name in fcb */  
   if (!parsfnm(line, &blk, 1))  
   {  
      printf("Error in call to parsfnm\n");  
      exit(1);  
   }  
   printf("Drive #%d  File: %s\n\n", blk.fcb_drive, blk.fcb_name);  

   /* open file with DOS FCB open file */  
   bdosptr(0x0F, &blk, 0);  

   /* save old dta, and set new one */  
   save_dta = getdta();  
   setdta(buffer);  

   /* set up info for the new dta */  
   blk.fcb_recsize = 128;  
   blk.fcb_random = 0L;  
   result = randbrd(&blk, 1);  

   /* check results from randbrd */  
   if (!result)  
      printf("Read OK\n\n");  
   else  
   {  
      perror("Error during read");  
      exit(1);  
   }  

   /* read in data from the new dta */  
   printf("The first 128 characters are:\n");  
   for (i=0; i<128; i++)  
      putchar(buffer[i]);  

   /* restore previous dta */  
   setdta(save_dta);  

   return 0;  
}  
   

函數名: randbwr  
功  能: 隨機塊寫  
用  法: int randbwr(struct fcp *fcbptr, int reccnt);  
程序例:  

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

int main(void)  
{  
   char far *save_dta;  
   char line[80];  
   char buffer[256] = "RANDBWR test!";  
   struct fcb blk;  
   int result;  

   /* get new file name from user */  
   printf("Enter a file name to create (no path - ie. a:file.dat\n");  
   gets(line);  

   /* parse the new file name to the dta */  
   parsfnm(line,&blk,1);  
   printf("Drive #%d  File: %s\n", blk.fcb_drive, blk.fcb_name);  

   /* request DOS services to create file */  
   if (bdosptr(0x16, &blk, 0) == -1)  
   {  
      perror("Error creating file");  
      exit(1);  
   }  

   /* save old dta and set new dta */  
   save_dta = getdta();  
   setdta(buffer);  

   /* write new records */  
   blk.fcb_recsize = 256;  
   blk.fcb_random = 0L;  
   result = randbwr(&blk, 1);  

   if (!result)  
      printf("Write OK\n");  
   else  
   {  
      perror("Disk error");  
      exit(1);  
   }  

   /* request DOS services to close the file */  
   if (bdosptr(0x10, &blk, 0) == -1)  
   {  
      perror("Error closing file");  
      exit(1);  
   }  

   /* reset the old dta */  
   setdta(save_dta);  

   return 0;  
}  
   
   

函數名: random  
功  能: 隨機數發生器  
用  法: int random(int num);  
程序例:  

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

/* prints a random number in the range 0 to 99 */  
int main(void)  
{  
   randomize();  
   printf("Random number in the 0-99 range: %d\n", random (100));  
   return 0;  
}  
   
   

函數名: randomize  
功  能: 初始化隨機數發生器  
用  法: void randomize(void);  
程序例:  

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

int main(void)  
{  
   int i;  

   randomize();  
   printf("Ten random numbers from 0 to 99\n\n");  
   for(i=0; i<10; i++)  
       printf("%d\n", rand() % 100);  
   return 0;  
}  
   
   

函數名: read  
功  能: 從文件中讀  
用  法: int read(int handle, void *buf, int nbyte);  
程序例:  

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

int main(void)  
{  
   void *buf;  
   int handle, bytes;  

   buf = malloc(10);  

/*  
   Looks for a file in the current directory named TEST.$$$ and attempts  
   to read 10 bytes from it.  To use this example you should create the  
   file TEST.$$$  
*/  
   if ((handle =  
      open("TEST.$$$", O_RDONLY | O_BINARY, S_IWRITE | S_IREAD)) == -1)  
   {  
      printf("Error Opening File\n");  
      exit(1);  
   }  

   if ((bytes = read(handle, buf, 10)) == -1) {  
      printf("Read Failed.\n");  
      exit(1);  
   }  
   else {  
      printf("Read: %d bytes read.\n", bytes);  
   }  
   return 0;  
}  
   
   

函數名: realloc  
功  能: 重新分配主存  
用  法: void *realloc(void *ptr, unsigned newsize);  
程序例:  

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

int main(void)  
{  
   char *str;  

   /* allocate memory for string */  
   str = malloc(10);  

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

   printf("String is %s\n  Address is %p\n", str, str);  
   str = realloc(str, 20);  
   printf("String is %s\n  New address is %p\n", str, str);  

   /* free memory */  
   free(str);  

   return 0;  
}  
   
   

函數名: rectangle  
功  能: 畫一個矩形  
用  法: void far rectangle(int left, int top, int right, int bottom);  
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 left, top, right, bottom;  

   /* 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 */  
   }  

   left = getmaxx() / 2 - 50;  
   top = getmaxy() / 2 - 50;  
   right = getmaxx() / 2 + 50;  
   bottom = getmaxy() / 2 + 50;  

   /* draw a rectangle */  
   rectangle(left,top,right,bottom);  

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

函數名: registerbgidriver  
功  能: 登錄已連接進來的圖形驅動程序代碼  
用  法: int registerbgidriver(void(*driver)(void));  
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;  

   /* register a driver that was added into graphics.lib */  
   errorcode = registerbgidriver(EGAVGA_driver);  

   /* report any registration errors */  
   if (errorcode < 0)  
   {  
      printf("Graphics error: %s\n", grapherrormsg(errorcode));  
      printf("Press any key to halt:");  
      getch();  
      exit(1); /* terminate with an error code */  
   }  

   /* 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 */  
   }  

   /* draw a line */  
   line(0, 0, getmaxx(), getmaxy());  

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

函數名: remove  
功  能: 刪除一個文件  
用  法: int remove(char *filename);  
程序例:  

#include <stdio.h>  

int main(void)  
{  
   char file[80];  

   /* prompt for file name to delete */  
   printf("File to delete: ");  
   gets(file);  

   /* delete the file */  
   if (remove(file) == 0)  
      printf("Removed %s.\n",file);  
   else  
      perror("remove");  

   return 0;  
}  
   
   

函數名: rename  
功  能: 重命名文件  
用  法: int rename(char *oldname, char *newname);  
程序例:  

#include <stdio.h>  

int main(void)  
{  
   char oldname[80], newname[80];  

   /* prompt for file to rename and new name */  
   printf("File to rename: ");  
   gets(oldname);  
   printf("New name: ");  
   gets(newname);  

   /* Rename the file */  
   if (rename(oldname, newname) == 0)  
      printf("Renamed %s to %s.\n", oldname, newname);  
   else  
      perror("rename");  

   return 0;  
}  
   
   

函數名: restorecrtmode  
功  能: 將屏幕模式恢復為先前的imitgraph設置  
用  法: void far restorecrtmode(void);  
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 x, y;  

   /* 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 */  
   }  

   x = getmaxx() / 2;  
   y = getmaxy() / 2;  

   /* output a message */  
   settextjustify(CENTER_TEXT, CENTER_TEXT);  
   outtextxy(x, y, "Press any key to exit graphics:");  
   getch();  

   /* restore system to text mode */  
   restorecrtmode();  
   printf("We're now in text mode.\n");  
   printf("Press any key to return to graphics mode:");  
   getch();  

   /* return to graphics mode */  
   setgraphmode(getgraphmode());  

   /* output a message */  
   settextjustify(CENTER_TEXT, CENTER_TEXT);  
   outtextxy(x, y, "We're back in graphics mode.");  
   outtextxy(x, y+textheight("W"), "Press any key to halt:");  

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

函數名: rewind  
功  能: 將文件指針重新指向一個流的開頭  
用  法: int rewind(FILE *stream);  
程序例:  

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

 int main(void)  
 {  
    FILE *fp;  
    char *fname = "TXXXXXX", *newname, first;  

    newname = mktemp(fname);  
    fp = fopen(newname,"w+");  
    fprintf(fp,"abcdefghijklmnopqrstuvwxyz");  
    rewind(fp);  
    fscanf(fp,"%c",&first);  
    printf("The first character is: %c\n",first);  
    fclose(fp);  
    remove(newname);  

    return 0;  
}  
   
   

函數名: rmdir  
功  能: 刪除DOS文件目錄  
用  法: int rmdir(char *stream);  
程序例:  

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

#define DIRNAME "testdir.$$$"  

int main(void)  
{  
   int stat;  

   stat = mkdir(DIRNAME);  
   if (!stat)  
          printf("Directory created\n");  
   else  
   {  
      printf("Unable to create directory\n");  
      exit(1);  
   }  

   getch();  
   system("dir/p");  
   getch();  

   stat = rmdir(DIRNAME);  
   if (!stat)  
          printf("\nDirectory deleted\n");  
   else  
   {  
   perror("\nUnable to delete directory\n");  
      exit(1);  
   }  

   return 0;  
}