C语言函数-P开头_C语言教程

函数名: parsfnm
功  能: 分析文件名
用  法: char *parsfnm (char *cmdline, struct fcb *fcbptr, int option);
程序例:

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

int main(void)
{
   char line[80];
   struct fcb blk;

   /* get file name */
   printf("Enter drive and file name (no path - ie. a:file.dat)\n");
   gets(line);

   /* put file name in fcb */
   if (parsfnm(line, &blk, 1) == NULL)
      printf("Error in parsfm call\n");
   else
      printf("Drive #%d  Name: %11s\n", blk.fcb_drive, blk.fcb_name);

   return 0;
}
 
 

函数名: peek
功  能: 检查存储单元
用  法: int peek(int segment, unsigned offset);
程序例:

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

int main(void)
{
   int value = 0;

   printf("The current status of your keyboard is:\n");
   value = peek(0x0040, 0x0017);
   if (value & 1)
      printf("Right shift on\n");
   else
      printf("Right shift off\n");

   if (value & 2)
      printf("Left shift on\n");
   else
      printf("Left shift off\n");

   if (value & 4)
      printf("Control key on\n");
   else
      printf("Control key off\n");

   if (value & 8)
      printf("Alt key on\n");
   else
      printf("Alt key off\n");

   if (value & 16)
      printf("Scroll lock on\n");
   else
      printf("Scroll lock off\n");

   if (value & 32)
      printf("Num lock on\n");
   else
      printf("Num lock off\n");

   if (value & 64)
      printf("Caps lock on\n");
   else
      printf("Caps lock off\n");

   return 0;
}
 
 

函数名: peekb
功  能: 检查存储单元
用  法: char peekb (int segment, unsigned offset);
程序例:

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

int main(void)
{
   int value = 0;

   printf("The current status of your keyboard is:\n");
   value = peekb(0x0040, 0x0017);
   if (value & 1)
      printf("Right shift on\n");
   else
      printf("Right shift off\n");

   if (value & 2)
      printf("Left shift on\n");
   else
      printf("Left shift off\n");

   if (value & 4)
      printf("Control key on\n");
   else
      printf("Control key off\n");

   if (value & 8)
      printf("Alt key on\n");
   else
      printf("Alt key off\n");

   if (value & 16)
      printf("Scroll lock on\n");
   else
      printf("Scroll lock off\n");

   if (value & 32)
      printf("Num lock on\n");
   else
      printf("Num lock off\n");

   if (value & 64)
      printf("Caps lock on\n");
   else
      printf("Caps lock off\n");

   return 0;
}
 
 

函数名: perror
功  能: 系统错误信息
用  法: void perror(char *string);
程序例:

#include <stdio.h>

int main(void)
{
   FILE *fp;

   fp = fopen("perror.dat", "r");
   if (!fp)
      perror("Unable to open file for reading");
   return 0;
}
 
 

函数名: pieslice
功  能: 绘制并填充一个扇形
用  法: void far pieslice(int x, int stanle, int endangle, int radius);
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;
   int stangle = 45, endangle = 135, radius = 100;

   /* 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;

   /* set fill style and draw a pie slice */
   setfillstyle(EMPTY_FILL, getmaxcolor());
   pieslice(midx, midy, stangle, endangle, radius);

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

函数名: poke
功  能: 存值到一个给定存储单元
用  法: void poke(int segment, int offset, int value);
程序例:

#include <dos.h>
#include <conio.h>

int main(void)
{
   clrscr();
   cprintf("Make sure the scroll lock key is off and press any key\r\n");
   getch();
   poke(0x0000,0x0417,16);
   cprintf("The scroll lock is now on\r\n");
   return 0;
}
 
 

函数名: pokeb
功  能: 存值到一个给定存储单元
用  法: void pokeb(int segment, int offset, char value);
程序例:

#include <dos.h>
#include <conio.h>

int main(void)
{
   clrscr();
   cprintf("Make sure the scroll lock key is off and press any key\r\n");
   getch();
   pokeb(0x0000,0x0417,16);
   cprintf("The scroll lock is now on\r\n");
   return 0;
}
 
 

函数名: poly
功  能: 根据参数产生一个多项式
用  法: double poly(double x, int n, double c[]);
程序例:

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

/* polynomial:  x**3 - 2x**2 + 5x - 1 */

int main(void)
{
   double array[] = { -1.0, 5.0, -2.0, 1.0 };
   double result;

   result = poly(2.0, 3, array);
   printf("The polynomial: x**3 - 2.0x**2 + 5x - 1 at 2.0 is %lf\n",
           result);
   return 0;
}
 
 

函数名: pow
功  能: 指数函数(x的y次方)
用  法: double pow(double x, double y);
程序例:

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

int main(void)
{
   double x = 2.0, y = 3.0;

   printf("%lf raised to %lf is %lf\n", x, y, pow(x, y));
   return 0;
}
 

函数名: pow10
功  能: 指数函数(10的p次方)
用  法: double pow10(int p);
程序例:

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

int main(void)
{
   double p = 3.0;

   printf("Ten raised to %lf is %lf\n", p, pow10(p));
   return 0;
}
 
 

函数名: printf
功  能: 产生格式化输出的函数
用  法: int printf(char *format...);
程序例:

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

#define I 555
#define R 5.5

int main(void)
{
   int i,j,k,l;
   char buf[7];
   char *prefix = buf;
   char tp[20];
   printf("prefix  6d      6o      8x        10.2e        "
          "10.2f\n");
   strcpy(prefix,"%");
   for (i = 0; i < 2; i++)
   {
      for (j = 0; j < 2; j++)
         for (k = 0; k < 2; k++)
     for (l = 0; l < 2; l++)
            {
               if (i==0)  strcat(prefix,"-");
               if (j==0)  strcat(prefix,"+");
               if (k==0)  strcat(prefix,"#");
               if (l==0)  strcat(prefix,"0");
               printf("%5s |",prefix);
               strcpy(tp,prefix);
               strcat(tp,"6d |");
               printf(tp,I);
               strcpy(tp,"");
               strcpy(tp,prefix);
               strcat(tp,"6o |");
               printf(tp,I);
               strcpy(tp,"");
               strcpy(tp,prefix);
               strcat(tp,"8x |");
               printf(tp,I);
               strcpy(tp,"");
               strcpy(tp,prefix);
        strcat(tp,"10.2e |");
        printf(tp,R);
        strcpy(tp,prefix);
        strcat(tp,"10.2f |");
        printf(tp,R);
        printf("  \n");
        strcpy(prefix,"%");
     }
       }
   return 0;
}
 
 

函数名: putc
功  能: 输出一字符到指定流中
用  法: int putc(int ch, FILE *stream);
程序例:

#include <stdio.h>

int main(void)
{
   char msg[] = "Hello world\n";
   int i = 0;

   while (msg[i])
      putc(msg[i++], stdout);
   return 0;
}
 
 

函数名: putch
功  能: 输出字符到控制台
用  法: int putch(int ch);
程序例:

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

int main(void)
{
   char ch = 0;

   printf("Input a string:");
   while ((ch != '\r'))
   {
      ch = getch();
      putch(ch);
   }
   return 0;
}
 
 

函数名: putchar
功  能: 在stdout上输出字符
用  法: int putchar(int ch);
程序例:

#include <stdio.h>

/* define some box-drawing characters */
#define LEFT_TOP  0xDA
#define RIGHT_TOP 0xBF
#define HORIZ     0xC4
#define VERT      0xB3
#define LEFT_BOT  0xC0
#define RIGHT_BOT 0xD9

int main(void)
{
   char i, j;

   /* draw the top of the box */
   putchar(LEFT_TOP);
   for (i=0; i<10; i++)
      putchar(HORIZ);
   putchar(RIGHT_TOP);
   putchar('\n');

   /* draw the middle */
   for (i=0; i<4; i++)
   {
      putchar(VERT);
      for (j=0; j<10; j++)
         putchar(' ');
      putchar(VERT);
      putchar('\n');
   }

   /* draw the bottom */
   putchar(LEFT_BOT);
   for (i=0; i<10; i++)
      putchar(HORIZ);
   putchar(RIGHT_BOT);
   putchar('\n');

   return 0;
}
 
 

函数名: putenv
功  能: 把字符串加到当前环境中
用  法: int putenv(char *envvar);
程序例:

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

int main(void)
{
   char *path, *ptr;
   int i = 0;

   /* get the current path environment */
   ptr = getenv("PATH");

   /* set up new path */
   path = malloc(strlen(ptr)+15);
   strcpy(path,"PATH=");
   strcat(path,ptr);
   strcat(path,";c:\\temp");

   /* replace the current path and display current environment */
   putenv(path);
   while (environ[i])
       printf("%s\n",environ[i++]);

   return 0;
}
 
 

函数名: putimage
功  能: 在屏幕上输出一个位图
用  法: void far putimage(int x, int y, void far *bitmap, int op);
程序例:

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

#define ARROW_SIZE 10

void draw_arrow(int x, int y);

int main(void)
{
   /* request autodetection */
   int gdriver = DETECT, gmode, errorcode;
   void *arrow;
   int x, y, maxx;
   unsigned int size;

   /* 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 */
   }

   maxx = getmaxx();
   x = 0;
   y = getmaxy() / 2;

   /* draw the image to be grabbed */
   draw_arrow(x, y);

   /* calculate the size of the image */
   size = imagesize(x, y-ARROW_SIZE, x+(4*ARROW_SIZE), y+ARROW_SIZE);

   /* allocate memory to hold the image */
   arrow = malloc(size);

   /* grab the image */
   getimage(x, y-ARROW_SIZE, x+(4*ARROW_SIZE), y+ARROW_SIZE, arrow);

   /* repeat until a key is pressed */
   while (!kbhit())
   {
      /* erase old image */
      putimage(x, y-ARROW_SIZE, arrow, XOR_PUT);

      x += ARROW_SIZE;
      if (x >= maxx)
          x = 0;

      /* plot new image */
      putimage(x, y-ARROW_SIZE, arrow, XOR_PUT);
   }

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

void draw_arrow(int x, int y)
{
   /* draw an arrow on the screen */
   moveto(x, y);
   linerel(4*ARROW_SIZE, 0);
   linerel(-2*ARROW_SIZE, -1*ARROW_SIZE);
   linerel(0, 2*ARROW_SIZE);
   linerel(2*ARROW_SIZE, -1*ARROW_SIZE);
}
 
 

函数名: putpixel
功  能: 在指定位置画一像素
用  法: void far putpixel (int x, int y, int pixelcolor);
程序例:

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

#define PIXEL_COUNT 1000
#define DELAY_TIME  100  /* in milliseconds */

int main(void)
{
   /* request autodetection */
   int gdriver = DETECT, gmode, errorcode;
   int i, x, y, color, maxx, maxy, maxcolor, seed;

   /* 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 */
   }

   maxx = getmaxx() + 1;
   maxy = getmaxy() + 1;
   maxcolor = getmaxcolor() + 1;

   while (!kbhit())
   {
      /* seed the random number generator */
      seed = random(32767);
      srand(seed);
      for (i=0; i<PIXEL_COUNT; i++)
      {
  x = random(maxx);
         y = random(maxy);
         color = random(maxcolor);
         putpixel(x, y, color);
      }

      delay(DELAY_TIME);
      srand(seed);
      for (i=0; i<PIXEL_COUNT; i++)
      {
  x = random(maxx);
  y = random(maxy);
  color = random(maxcolor);
  if (color == getpixel(x, y))
     putpixel(x, y, 0);
      }
   }

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

函数名: puts
功  能: 送一字符串到流中
用  法: int puts(char *string);
程序例:

#include <stdio.h>
int main(void)
{
   char string[] = "This is an example output string\n";

   puts(string);
   return 0;
}
 
 

函数名: puttext
功  能: 将文本从存储区拷贝到屏幕
用  法: int puttext(int left, int top, int right, int bottom, void *source);
程序例:

#include <conio.h>
int main(void)
{
   char buffer[512];

   /* put some text to the console */
   clrscr();
   gotoxy(20, 12);
   cprintf("This is a test.  Press any key to continue ...");
   getch();

   /* grab screen contents */
   gettext(20, 12, 36, 21,buffer);
   clrscr();

   /* put selected characters back to the screen */
   gotoxy(20, 12);
   puttext(20, 12, 36, 21, buffer);
   getch();

   return 0;
}
 
 

函数名: putw
功  能: 把一字符或字送到流中
用  法: int putw(int w, FILE *stream);
程序例:

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

#define FNAME "test.$$$"

int main(void)
{
   FILE *fp;
   int word;

   /* place the word in a file */
   fp = fopen(FNAME, "wb");
   if (fp == NULL)
   {
      printf("Error opening file %s\n", FNAME);
      exit(1);
   }

   word = 94;
   putw(word,fp);
   if (ferror(fp))
       printf("Error writing to file\n");
   else
       printf("Successful write\n");
   fclose(fp);

   /* reopen the file */
   fp = fopen(FNAME, "rb");
   if (fp == NULL)
   {
      printf("Error opening file %s\n", FNAME);
      exit(1);
   }

   /* extract the word */
   word = getw(fp);
   if (ferror(fp))
       printf("Error reading file\n");
   else
       printf("Successful read: word = %d\n", word);

   /* clean up */
   fclose(fp);
   unlink(FNAME);

   return 0;
}

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