C语言库函数(P类字母)
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;
}
