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 #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 #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 #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; } 函数名: eof 功 能: 检测文件结束 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 #include #include void main(int argc, char *argv[]) { int i; printf("Command line arguments:\n"); for (i=0; i

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