C語言函數大全(e開頭)

函數名: ecvt

功能: 把一個浮點數轉換為字符串

用法: char ecvt(double value, int ndigit, int *decpt, int *sign);

程序例:

#include
#include
#include
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;
}

函數名: ellipse

功能: 畫一橢圓

用法: void far ellipse(int x, int y, int stangle, int endangle,

int xradius, int yradius);

程序例:

#include
#include
#include
#include
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;
}

函數名: enable

功能: 開放硬件中斷

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
#include
#include
/* 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;
}

函數名: eof

功能: 檢測文件結束

用法: int eof(int *handle);

程序例:

#include
#include
#include
#include
#include
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;
}

函數名: exec...

功能: 裝入並運行其它程序的函數

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
#include
#include
void main(int argc, char *argv[])
{
int i;
printf("Command line arguments:\n");
for (i=0; 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);
}

函數名: exit

功能: 終止程序

用法: void exit(int status);

程序例:

#include
#include
#include
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;
}

函數名: exp

功能: 指數函數

用法: double exp(double x);

程序例:

#include
#include
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;
}