fe.txt

c语言编程宝典

   
   
   
   fe
函数名: ecvt
功 能: 把一个浮点数转换为字符串
用 法: char ecvt(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: ellipse
功 能: 画一椭圆
用 法: void far ellipse(int x, int y, int stangle, int endangle,
 int xradius, int yradius);
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 = 0, endangle = 360;
 int xradius = 100, yradius = 50;
 /* 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 */
 }
 midx = getmaxx() / 2;
 midy = getmaxy() / 2;
 setcolor(getmaxcolor());
 /* draw ellipse */
 ellipse(midx, midy, stangle, endangle,
 xradius, yradius);
 /* clean up */
 getch();
 closegraph();
 return 0;
}
函数名: enable
功 能: 开放硬件中断
用 法: void enable(void);
程序例:
/* ** NOTE:
This is an interrupt service routine. You can NOT compile this program
with Test Stack Overflow turned on and get an executable file which
will
operate correctly.
*/
#include <stdio.h>
#include <dos.h>
#include <conio.h>
/* The clock tick interrupt */
#define INTR 0X1C
void interrupt ( *oldhandler)(void);
int count=0;
void interrupt handler(void)
{
/*
 disable interrupts during the handling of the interrupt
*/
 disable();
/* increase the global counter */
 count++;
/*
 re enable interrupts at the end of the handler
*/
 enable();
/* call the old routine */
 oldhandler();
}
int main(void)
{
/* save the old interrupt vector */
 oldhandler = getvect(INTR);
/* install the new interrupt handler */
 setvect(INTR, handler);
/* loop until the counter exceeds 20 */
 while (count < 20)
 printf("count is %d\n",count);
/* reset the old interrupt handler */
 setvect(INTR, oldhandler);
 return 0;
}
函数名: eof
功 能: 检测文件结束
用 法: int eof(int *handle);
程序例:
#include <sys\stat.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
 int handle;
 char msg[] = "This is a test";
 char ch;
 /* create a file */
 handle = open("DUMMY.FIL",
 O_CREAT | O_RDWR,
 S_IREAD | S_IWRITE);
 /* write some data to the file */
 write(handle, msg, strlen(msg));
 /* seek to the beginning of the file */
 lseek(handle, 0L, SEEK_SET);
 /*
 reads chars from the file until hit
EOF
 */
 do
 {
 read(handle, &ch, 1);
 printf("%c", ch);
 } while (!eof(handle));
 close(handle);
 return 0;
}
函数名: exec...
功 能: 装入并运行其它程序的函数
用 法: int execl(char *pathname, char *arg0, arg1, ..., argn,
NULL);
int execle(char *pathname, char *arg0, arg1, ..., argn, NULL,
 char *envp[]);
int execlp(char *pathname, char *arg0, arg1, .., NULL);
int execple(char *pathname, char *arg0, arg1, ..., NULL,
 char *envp[]);
int execv(char *pathname, char *argv[]);
int execve(char *pathname, char *argv[], char *envp[]);
int execvp(char *pathname, char *argv[]);
int execvpe(char *pathname, char *argv[], char *envp[]);
程序例:
/* execv example */
#include <process.h>
#include <stdio.h>
#include <errno.h>
void main(int argc, char *argv[])
{
 int i;
 printf("Command line arguments:\n");
 for (i=0; i<argc; i++)
 printf("[%2d] : %s\n", i, argv[i]);
 printf("About to exec child with arg1 arg2 ...\n");
 execv("CHILD.EXE", argv);
 perror("exec error");
 exit(1);
}
函数名: exit
功 能: 终止程序
用 法: void exit(int status);
程序例:
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
int main(void)
{
 int status;
 printf("Enter either 1 or 2\n");
 status = getch();
 /* Sets DOS errorlevel */
 exit(status - '0');
/* Note: this line is never reached */
 return 0;
}
函数名: exp
功 能: 指数函数
用 法: double exp(double x);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
 double result;
 double x = 4.0;
 result = exp(x);
 printf("'e' raised to the power \
 of %lf (e ^ %lf) = %lf\n",
 x, x, result);
 return 0;
}
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