} 



midx = getmaxx() / 2; 
midy = getmaxy() / 2; 
setcolor(getmaxcolor()); 



/* for centering screen messages */ 
settextjustify(CENTER_TEXT, CENTER_TEXT); 



/* output a message to the screen */ 
outtextxy(midx, midy, "press any key to clear the screen:"); 



/* wait for a key */ 
getch(); 



/* clear the screen */ 
cleardevice(); 



/* output another message */ 
outtextxy(midx, midy, "press any key to quit:"); 



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






函數(shù)名: clearerr 
功 能: 復(fù)位錯誤標(biāo)志 
用 法:void clearerr(FILE *stream); 
程序例: 



#include <stdio.h> 



int main(void) 
{ 
FILE *fp; 
char ch; 



/* open a file for writing */ 
fp = fopen("DUMMY.FIL", "w"); 



/* force an error condition by attempting 
to read */ 
ch = fgetc(fp); 
printf("%c\n",ch); 



if (ferror(fp)) 
{ 
/* display an error message */ 
printf("Error reading from DUMMY.FIL\n"); 



/* reset the error and EOF indicators */ 

clearerr(fp); 
} 



fclose(fp); 
return 0; 
} 






函數(shù)名: clearviewport 
功 能: 清除圖形視區(qū) 
用 法: void far clearviewport(void); 
程序例: 



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



#define CLIP_ON 1 /* activates clipping in 
viewport */ 



int main(void) 
{ 
/* request auto detection */ 
int gdriver = DETECT, gmode, errorcode; 
int ht; 



/* 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 */ 
} 



setcolor(getmaxcolor()); 
ht = textheight("W"); 



/* message in default full-screen viewport 
*/ 
outtextxy(0, 0, "* <-- (0, 0) in default viewport"); 



/* create a smaller viewport */ 
setviewport(50, 50, getmaxx()-50, getmaxy()-50, CLIP_ON); 



/* display some messages */ 
outtextxy(0, 0, "* <-- (0, 0) in smaller viewport"); 
outtextxy(0, 2*ht, "Press any key to clear viewport:"); 



/* wait for a key */ 
getch(); 



/* clear the viewport */ 
clearviewport(); 



/* output another message */ 
outtextxy(0, 0, "Press any key to quit:"); 



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






函數(shù)名: _close, close 
功 能: 關(guān)閉文件句柄 
用 法: int close(int handle); 
程序例: 



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



main() 
{ 
int handle; 
char buf[11] = "0123456789"; 



/* create a file containing 10 bytes */ 

handle = open("NEW.FIL", O_CREAT); 
if (handle > -1) 
{ 
write(handle, buf, strlen(buf)); 



/* close the file */ 
close(handle); 
} 
else 
{ 
printf("Error opening file\n"); 
} 
return 0; 
} 






函數(shù)名: clock 
功 能: 確定處理器時間 
用 法: clock_t clock(void); 
程序例: 



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



int main(void) 
{ 
clock_t start, end; 
start = clock(); 



delay(2000); 



end = clock(); 
printf("The time was: %f\n", (end - start) / CLK_TCK); 



return 0; 
} 






函數(shù)名: closegraph 
功 能: 關(guān)閉圖形系統(tǒng) 
用 法: void far closegraph(void); 
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 x, y; 



/* initialize graphics mode */ 
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 */ 
} 



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



/* output a message */ 
settextjustify(CENTER_TEXT, CENTER_TEXT); 
outtextxy(x, y, "Press a key to close the graphics system:"); 



/* wait for a key */ 
getch(); 



/* closes down the graphics system */ 
closegraph(); 



printf("We re now back in text mode.\n"); 

printf("Press any key to halt:"); 
getch(); 
return 0; 
} 






函數(shù)名: clreol 
功 能: 在文本窗口中清除字符到行末 
用 法: void clreol(void); 
程序例: 



#include <conio.h> 



int main(void) 



{ 
clrscr(); 
cprintf("The function CLREOL clears all characters from the\r\n"); 
cprintf("cursor position to the end of the line within the\r\n"); 
cprintf("current text window, without moving the cursor.\r\n"); 
cprintf("Press any key to continue . . ."); 
gotoxy(14, 4); 
getch(); 



clreol(); 
getch(); 



return 0; 
} 





函數(shù)名: clrscr 
功 能: 清除文本模式窗口 
用 法: void clrscr(void); 
程序例: 



#include <conio.h> 



int main(void) 
{ 
int i; 



clrscr(); 
for (i = 0; i < 20; i++) 
cprintf("%d\r\n", i); 
cprintf("\r\nPress any key to clear screen"); 
getch(); 



clrscr(); 
cprintf("The screen has been cleared!"); 
getch(); 



return 0; 
} 






函數(shù)名: coreleft 
功 能: 返回未使用內(nèi)存的大小 
用 法: unsigned coreleft(void); 
程序例: 



#include <stdio.h> 
#include <alloc.h> 



int main(void) 
{ 
printf("The difference between the highest allocated block and\n"); 
printf("the top of the heap is: %lu bytes\n", (unsigned long) coreleft()); 




return 0; 
} 




函數(shù)名: cos 
功 能: 余弦函數(shù) 
用 法: double cos(double x); 
程序例: 



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



int main(void) 
{ 
double result; 
double x = 0.5; 



result = cos(x); 
printf("The cosine of %lf is %lf\n", x, result); 
return 0; 
} 






函數(shù)名: cosh 
功 能: 雙曲余弦函數(shù) 
用 法: dluble cosh(double x); 
程序例: 



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



int main(void) 
{ 
double result; 
double x = 0.5; 



result = cosh(x); 
printf("The hyperboic cosine of %lf is %lf\n", x, result); 
return 0; 
} 






函數(shù)名: country 
功 能: 返回與國家有關(guān)的信息 
用 法: struct COUNTRY *country(int countrycode, struct country *country); 

程序例: 



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



#define USA 0 



int main(void) 
{ 
struct COUNTRY country_info; 



country(USA, &country_info); 
printf("The currency symbol for the USA is: %s\n", 
country_info.co_curr); 

return 0; 
} 





函數(shù)名: cprintf 
功 能: 送格式化輸出至屏幕 
用 法: int cprintf(const char *format[, argument, ...]); 
程序例: 



#include <conio.h> 



int main(void) 
{ 
/* clear the screen */ 
clrscr(); 



/* create a text window */ 
window(10, 10, 80, 25); 



/* output some text in the window */ 
cprintf("Hello world\r\n"); 



/* wait for a key */ 
getch(); 
return 0; 
} 





函數(shù)名: cputs 
功 能: 寫字符到屏幕 
用 法: void cputs(const char *string); 
程序例: 



#include <conio.h> 



int main(void) 
{ 
/* clear the screen */ 
clrscr(); 



/* create a text window */ 
window(10, 10, 80, 25); 



/* output some text in the window */ 
cputs("This is within the window\r\n"); 



/* wait for a key */ 
getch(); 
return 0; 
} 





函數(shù)名: _creat creat 
功 能: 創(chuàng)建一個新文件或重寫一個已存在的文件 
用 法: int creat (const char *filename, int permiss); 
程序例: 



#include <sys\stat.h> 
#include <string.h> 
#include <fcntl.h> 
#include <io.h> 



int main(void) 
{ 
int handle; 
char buf[11] = "0123456789"; 



/* change the default file mode from text 
to binary */ 
_fmode = O_BINARY; 



/* create a binary file for reading and 
writing */ 
handle = creat("DUMMY.FIL", S_IREAD | S_IWRITE); 



/* write 10 bytes to the file */ 
write(handle, buf, strlen(buf)); 



/* close the file */ 
close(handle); 
return 0; 
} 




函數(shù)名: creatnew 
功 能: 創(chuàng)建一個新文件 
用 法: int creatnew(const char *filename, int attrib); 
程序例: 



#include <string.h> 
#include <stdio.h> 
#include <errno.h> 
#include <dos.h> 
#include <io.h> 



int main(void) 
{ 
int handle; 
char buf[11] = "0123456789"; 



/* attempt to create a file that doesn t 
already exist */ 
handle = creatnew("DUMMY.FIL", 0); 



if (handle == -1) 
printf("DUMMY.FIL already exists.\n"); 
else 
{ 
printf("DUMMY.FIL successfully created.\n"); 
write(handle, buf, strlen(buf)); 
close(handle); 
} 
return 0; 
} 




函數(shù)名: creattemp 
功 能: 創(chuàng)建一個新文件或重寫一個已存在的文件 
用 法: int creattemp(const char *filename, int attrib); 
程序例: 



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



int main(void) 
{ 
int handle; 
char pathname[128]; 



strcpy(pathname, "\\"); 



/* create a unique file in the root directory 
*/ 
handle = creattemp(pathname, 0); 



printf("%s was the unique file created.\n", 
pathname); 
close(handle); 
return 0; 
} 




函數(shù)名: cscanf 
功 能: 從控制臺執(zhí)行格式化輸入 
用 法: int cscanf(char *format[,argument, ...]); 
程序例: 



#include <conio.h> 



int main(void) 
{ 
char string[80]; 



/* clear the screen */ 
clrscr(); 



/* Prompt the user for input */ 
cprintf("Enter a string with no spaces:"); 



/* read the input */ 
cscanf("%s", string); 



/* display what was read */ 
cprintf("\r\nThe string entered is: %s", string); 
return 0; 
} 





函數(shù)名: ctime 
功 能: 把日期和時間轉(zhuǎn)換為字符串 
用 法: char *ctime(const time_t *time); 
程序例: 



#include <stdio.h> 
#include <time.h> 



int main(void) 
{ 
time_t t; 



time(&t); 
printf("Today s date and time: %s\n", ctime(&t)); 
return 0; 
} 





函數(shù)名: ctrlbrk 
功 能: 設(shè)置Ctrl-Break處理程序 
用 法: void ctrlbrk(*fptr)(void); 
程序例: