c语言库函数(s类字母) - 1.txt

较为全面地介绍了C语言的各种库函数

函数名: sbrk  
功  能: 改变数据段空间位置  
用  法: char *sbrk(int incr);  
程序例:  

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

int main(void)  
{  
   printf("Changing allocation with sbrk()\n");  
   printf("Before sbrk() call: %lu bytes free\n",  
   (unsigned long) coreleft());  
   sbrk(1000);  
   printf(" After sbrk() call: %lu bytes free\n",  
   (unsigned long) coreleft());  
   return 0;  
}  
   
   

函数名: scanf  
功  能: 执行格式化输入  
用  法: int scanf(char *format[,argument,...]);  
程序例:  

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

int main(void)  
{  
   char label[20];  
   char name[20];  
   int entries = 0;  
   int loop, age;  
   double salary;  

   struct Entry_struct  
   {  
      char  name[20];  
      int   age;  
      float salary;  
   } entry[20];  

/* Input a label as a string of characters restricting to 20 characters */  
   printf("\n\nPlease enter a label for the chart: ");  
   scanf("%20s", label);  
   fflush(stdin);  /* flush the input stream in case of bad input */  

/* Input number of entries as an integer */  
   printf("How many entries will there be? (less than 20) ");  
   scanf("%d", &entries);  
   fflush(stdin);   /* flush the input stream in case of bad input */  

/* input a name restricting input to only letters upper or lower case */  
   for (loop=0;loop<entries;++loop)  
   {  
      printf("Entry %d\n", loop);  
      printf("  Name   : ");  
      scanf("%[A-Za-z]", entry[loop].name);  
      fflush(stdin);  /* flush the input stream in case of bad input */  

/* input an age as an integer */  
      printf("  Age    : ");  
      scanf("%d", &entry[loop].age);  
      fflush(stdin);  /* flush the input stream in case of bad input */  

/* input a salary as a float */  
      printf("  Salary : ");  
      scanf("%f", &entry[loop].salary);  
      fflush(stdin); /* flush the input stream in case of bad input */  
   }  

/* Input a name, age and salary as a string, integer, and double */  
   printf("\nPlease enter your name, age and salary\n");  
   scanf("%20s %d %lf", name, &age, &salary);  
   

/* Print out the data that was input */  
   printf("\n\nTable %s\n",label);  
   printf("Compiled by %s  age %d  $%15.2lf\n", name, age, salary);  
   printf("-----------------------------------------------------\n");  
   for (loop=0;loop<entries;++loop)  
      printf("%4d | %-20s | %5d | %15.2lf\n",  
         loop + 1,  
  entry[loop].name,  
  entry[loop].age,  
         entry[loop].salary);  
   printf("-----------------------------------------------------\n");  
   return 0;  
}  
   
   

函数名: searchpath  
功  能: 搜索DOS路径  
用  法: char *searchpath(char *filename);  
程序例:  

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

int main(void)  
{  
   char *p;  

   /* Looks for TLINK and returns a pointer  
      to the path  */  
   p = searchpath("TLINK.EXE");  
   printf("Search for TLINK.EXE : %s\n", p);  

   /* Looks for non-existent file  */  
   p = searchpath("NOTEXIST.FIL");  
   printf("Search for NOTEXIST.FIL : %s\n", p);  

   return 0;  
}  
   
   

函数名: sector  
功  能: 画并填充椭圆扇区  
用  法: void far sector(int x, int y, int stangle, int endangle);  
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 midx, midy, i;  
   int stangle = 45, endangle = 135;  
   int xrad = 100, yrad = 50;  

   /* 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 */  
   }  

   midx = getmaxx() / 2;  
   midy = getmaxy() / 2;  

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

      /* draw the sector slice */  
      sector(midx, midy, stangle, endangle, xrad, yrad);  

      getch();  
   }  

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

函数名: segread  
功  能: 读段寄存器值  
用  法: void segread(struct SREGS *segtbl);  
程序例:  

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

int main(void)  
{  
   struct SREGS segs;  

   segread(&segs);  
   printf("Current segment register settings\n\n");  
   printf("CS: %X   DS: %X\n", segs.cs, segs.ds);  
   printf("ES: %X   SS: %X\n", segs.es, segs.ss);  

   return 0;  
}  
   
   

函数名: setactivepage  
功  能: 设置图形输出活动页  
用  法: void far setactivepage(int pagenum);  
程序例:  

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

int main(void)  
{  
   /* select a driver and mode that supports */  
   /* multiple pages.                        */  
   int gdriver = EGA, gmode = EGAHI, errorcode;  
   int x, y, ht;  

   /* 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;  
   ht = textheight("W");  

   /*  select the off screen page for drawing */  
   setactivepage(1);  

   /* draw a line on page #1 */  
   line(0, 0, getmaxx(), getmaxy());  

   /* output a message on page #1 */  
   settextjustify(CENTER_TEXT, CENTER_TEXT);  
   outtextxy(x, y, "This is page #1:");  
   outtextxy(x, y+ht, "Press any key to halt:");  

   /* select drawing to page #0 */  
   setactivepage(0);  

   /* output a message  on page #0 */  
   outtextxy(x, y, "This is page #0.");  
   outtextxy(x, y+ht, "Press any key to view page #1:");  
   getch();  

   /* select page #1 as the visible page */  
   setvisualpage(1);  

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

函数名: setallpallette  
功  能: 按指定方式改变所有的调色板颜色  
用  法: void far setallpallette(struct palette, far *pallette);  
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;  
   struct palettetype pal;  
   int color, maxcolor, ht;  
   int y = 10;  
   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 */  
   }  

   maxcolor = getmaxcolor();  
   ht = 2 * textheight("W");  

   /* grab a copy of the palette */  
   getpalette(&pal);  

   /* display the default palette colors */  
   for (color=1; color<=maxcolor; color++)  
   {  
      setcolor(color);  
      sprintf(msg, "Color: %d", color);  
      outtextxy(1, y, msg);  
      y += ht;  
   }  

   /* wait for a key */  
   getch();  

   /* black out the colors one by one */  
   for (color=1; color<=maxcolor; color++)  
   {  
      setpalette(color, BLACK);  
      getch();  
   }  

   /* restore the palette colors */  
   setallpalette(&pal);  

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

函数名: setaspectratio  
功  能: 设置图形纵横比  
用  法: void far setaspectratio(int xasp, int yasp);  
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 xasp, yasp, midx, midy;  

   /* 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 */  
   }  

   midx = getmaxx() / 2;  
   midy = getmaxy() / 2;  
   setcolor(getmaxcolor());  

   /* get current aspect ratio settings */  
   getaspectratio(&xasp, &yasp);  

   /* draw normal circle */  
   circle(midx, midy, 100);  
   getch();  

   /* claer the screen */  
   cleardevice();  

   /* adjust the aspect for a wide circle */  
   setaspectratio(xasp/2, yasp);  
   circle(midx, midy, 100);  
   getch();  

   /* adjust the aspect for a narrow circle */  
   cleardevice();  
   setaspectratio(xasp, yasp/2);  
   circle(midx, midy, 100);  

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

函数名: setbkcolor  
功  能: 用调色板设置当前背景颜色  
用  法: void far setbkcolor(int color);  
程序例:  

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

int main(void)  
{  
   /* select a driver and mode that supports */  
   /* multiple background colors.            */  
   int gdriver = EGA, gmode = EGAHI, errorcode;  
   int bkcol, maxcolor, x, y;  
   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 */  
   }  

   /* maximum color index supported */  
   maxcolor = getmaxcolor();  

   /* for centering text messages */  
   settextjustify(CENTER_TEXT, CENTER_TEXT);  
   x = getmaxx() / 2;  
   y = getmaxy() / 2;  

   /* loop through the available colors */  
   for (bkcol=0; bkcol<=maxcolor; bkcol++)  
   {  
      /* clear the screen */  
      cleardevice();  

      /* select a new background color */  
      setbkcolor(bkcol);  

      /* output a messsage */  
      if (bkcol == WHITE)  
  setcolor(EGA_BLUE);  
      sprintf(msg, "Background color: %d", bkcol);  
      outtextxy(x, y, msg);  
      getch();  
   }  

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

函数名: setblock  
功  能: 修改先前已分配的DOS存储段大小  
用  法: int setblock(int seg, int newsize);  
程序例:  

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

int main(void)  
{  
   unsigned int size, segp;  
   int stat;  

   size = 64; /* (64 x 16) = 1024 bytes */  
   stat = allocmem(size, &segp);  
   if (stat == -1)  
      printf("Allocated memory at segment: %X\n", segp);  
   else  
   {  
      printf("Failed: maximum number of paragraphs available is %d\n",  
      stat);  
      exit(1);  
   }  

   stat = setblock(segp, size * 2);  
   if (stat == -1)  
      printf("Expanded memory block at segment: %X\n", segp);  
   else  
      printf("Failed: maximum number of paragraphs available is %d\n",  
             stat);  

   freemem(segp);  

   return 0;  
}  
   
   

函数名: setbuf  
功  能: 把缓冲区与流相联  
用  法: void setbuf(FILE *steam, char *buf);  
程序例:  

#include <stdio.h>  

/* BUFSIZ is defined in stdio.h */  
char outbuf[BUFSIZ];  

int main(void)  
{  
   /* attach a buffer to the standard output stream */  
   setbuf(stdout, outbuf);  

   /* put some characters into the buffer */  
   puts("This is a test of buffered output.\n\n");  
   puts("This output will go into outbuf\n");  
   puts("and won't appear until the buffer\n");  
   puts("fills up or we flush the stream.\n");  

   /* flush the output buffer */  
   fflush(stdout);  

   return 0;