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C语言函数详解
&&C语言函数详解ppt
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第4章节简单C程序的设计.ppt 42页
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第4章节简单C程序的设计
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格式输入输出函数 4.5.1
输出函数printf( ) 在使用 printf 函数时，还有几点要说明： 除了 X,E,G外其他用小写，如％d不能写成％D。 上面介绍的d,o,x,c,s,f,e,g等字符，如用在“％”后面就作为格式符号。一个格式说明以“％”开头，以上述9个格式字符之一为结束，中间可以插入附加格式字符（也称修饰符）。例如：
printf(“c=%cf=%fs=%s”,c,f,s); 如果想输出字符“％”，则应该在“格式控制”字符串中用连续两个％表示，如:
printf（”％f％％”，1.0／3）；
0.333333％ Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright
Aspose Pty Ltd. 4．5
格式输入输出函数 4.5.2 输入函数scanf( ) 1.一般形式： scanf(“格式控制”，输入变量地址列表)； 说明： “格式控制”的含义同printf函数，具体见下页；“地址列表”是由若干个地址组成的表列，可以是变量的地址或字符串的首地址。
Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright
Aspose Pty Ltd. scanf格式字符
用来输入十进制整数。
用来输入八进制整数。
用来输入十六进制整数。
用来输入单个字符。
用来输入字符串，将字符串送到一个字符数组中，在输入时
以非空白字符开始，以第一个空白字符结束。字符串以串结
束标志“＼0”作为其最后一个字符。
用来输入实数，可以用小数形式或指数形式输入。
与f作用相同，e与f可以互相替换。 附加的格式说明字符
用于输入长整型数据（可用％ld,％lo，％lx等），以及
double型数据（用％lf或％1e）。
用于输入短整型数据（可用％hd，％ho，％hx）。
域宽（应为一正整数），指定输入数据所占宽度（列数）。
表示本输入项在读入后不赋给相应的变量。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright
Aspose Pty Ltd. 2.格式说明：
①对unsigned型数据，可以用％u、%d或％o、％x格式输入； ②m域宽可自动截取，空格可以作为数据分隔符。
void main(void) { int i,j;
scanf(&%3d%3d&,&i,&j);
printf(&%d\n%d&,i,j);} 输入123456 系统自动将123赋给a，456赋给b，也可用于字符型，如： scanf（”％3c”，&ch）; 输入3个字符，把第一个字符赋给ch，例如输入abc，ch得到字符’a’。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright
Aspose Pty Ltd. ③实型变量输入时不能规定精度；
scanf（“%7.2f”,&a）;
ERROR! ④％后的“*”附加说明符，用来表示跳过它相应的数
据。例如：
scanf（”％2d ％*3d ％2d＼n”,&a,&b）;
如果输入如下信息：
则系统将12赋给a, ％*3d表示读入3位整数但不赋给任何变量，然后再读入2位整数67赋给b.在利用现成的一批数据时，有时不需要其中的某些数据时，可用该法跳过它们。
Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile . Copyright
Aspose Pty Ltd. 3.使用scanf函数的中应注意的问题: ①scanf函数中的“格式控制”后面应当是变量地址，而不应是变量名。例如，如果a,b为整型变量，则
scanf（”％d,％d”，a,b）； ERROR! ②如果在“格式控制”
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一共分为3个小节，1小节给定一个连接，该连接给了一些常用标准c的函数使用说明，但是不够全面。2小结按字母顺序排列，几乎覆盖了c中常用的函数，同时有些函数不在unix系统中支持了。3小节描述了unix系统中常用系统调用的使用说明。
1、【下面这个连接给出了一些c库的函数说明使用例程，但是不够全面，可以作为参考】
2、【如下对C语言库函数按字母顺序描述,如果上面连接中找不到，可以到这里查找到，需要说明的是，有些函数在新的libc中已经不提供了，如果要查找unix系统常用系统调用函数使用说明，请到小节3查找】
函数名: abort
功 能: 异常终止一个进程
用 法: void abort(void);
#include ;
#include ;
int main(void)
printf("Calling abort()\n");
return 0; /* This is never reached */
函数名: abs
功 能: 求整数的绝对值
用 法: int abs(int i);
#include ;
#include ;
int main(void)
int number = -1234;
printf("number: %d absolute value: %d\n", number, abs(number));
函数名: absread, abswirte
功 能: 绝对磁盘扇区读、写数据
用 法: int absread(int drive, int nsects, int sectno, void *buffer);
int abswrite(int drive, int nsects, in tsectno, void *buffer);
/* absread example */
#include ;
#include ;
#include ;
#include ;
int main(void)
int i, strt, ch_out,
char buf[512];
printf("Insert a diskette into drive A and press any key\n");
sector = 0;
if (absread(0, 1, sector, &buf) != 0)
perror("Disk problem");
printf("Read OK\n");
for (i=0; i<80; i++)
ch_out = buf[strt+i];
putchar(ch_out);
printf("\n");
return(0);
函数名: access
功 能: 确定文件的访问权限
用 法: int access(const char *filename, int amode);
#include ;
#include ;
int file_exists(char *filename);
int main(void)
printf("Does NOTEXIST.FIL exist: %s\n",
file_exists("NOTEXISTS.FIL") ? "YES" : "NO");
int file_exists(char *filename)
return (access(filename, 0) == 0);
函数名: acos
功 能: 反余弦函数
用 法: double acos(double x);
#include ;
#include ;
int main(void)
double x = 0.5;
result = acos(x);
printf("The arc cosine of %lf is %lf\n", x, result);
函数名: allocmem
功 能: 分配DOS存储段
用 法: int allocmem(unsigned size, unsigned *seg);
#include ;
#include ;
#include ;
int main(void)
unsigned int size,
size = 64; /* (64 x 16) = 1024 bytes */
stat = allocmem(size, &segp);
if (stat == -1)
printf("Allocated memory at segment: %x\n", segp);
printf("Failed: maximum number of paragraphs available is %u\n",
函数名: arc
功 能: 画一弧线
用 法: void far arc(int x, int y, int stangle, int endangle, int radius);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
int stangle = 45, endangle = 135;
int radius = 100;
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult(); /* an error occurred */
if (errorcode != grOk)
printf("Graphics error: %s\n", grapherrormsg(errorcode));
printf("Press any key to halt:");
exit(1); /* terminate with an error code */
midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());
/* draw arc */
arc(midx, midy, stangle, endangle, radius);
/* clean up */
closegraph();
函数名: asctime
功 能: 转换日期和时间为ASCII码
用 法: char *asctime(const struct tm *tblock);
#include ;
#include ;
#include ;
int main(void)
char str[80];
/* sample loading of tm structure */
t.tm_sec = 1; /* Seconds */
t.tm_min = 30; /* Minutes */
t.tm_hour = 9; /* Hour */
t.tm_mday = 22; /* Day of the Month */
t.tm_mon = 11; /* Month */
t.tm_year = 56; /* Year - does not include century */
t.tm_wday = 4; /* Day of the week */
t.tm_yday = 0; /* Does not show in asctime */
t.tm_isdst = 0; /* Is Daylight SavT does not show in asctime */
/* converts structure to null terminated
strcpy(str, asctime(&t));
printf("%s\n", str);
函数名: asin
功 能: 反正弦函数
用 法: double asin(double x);
#include ;
#include ;
int main(void)
double x = 0.5;
result = asin(x);
printf("The arc sin of %lf is %lf\n", x, result);
return(0);
函数名: assert
功 能: 测试一个条件并可能使程序终止
用 法: void assert(int test);
#include ;
#include ;
#include ;
struct ITEM {
/* add item to list, make sure list is not null */
void additem(struct ITEM *itemptr) {
assert(itemptr != NULL);
/* add item to list */
int main(void)
additem(NULL);
函数名: atan
功 能: 反正切函数
用 法: double atan(double x);
#include ;
#include ;
int main(void)
double x = 0.5;
result = atan(x);
printf("The arc tangent of %lf is %lf\n", x, result);
return(0);
函数名: atan2
功 能: 计算Y/X的反正切值
用 法: double atan2(double y, double x);
#include ;
#include ;
int main(void)
double x = 90.0, y = 45.0;
result = atan2(y, x);
printf("The arc tangent ratio of %lf is %lf\n", (y / x), result);
函数名: atexit
功 能: 注册终止函数
用 法: int atexit(atexit_t func);
#include ;
#include ;
void exit_fn1(void)
printf("Exit function #1 called\n");
void exit_fn2(void)
printf("Exit function #2 called\n");
int main(void)
/* post exit function #1 */
atexit(exit_fn1);
/* post exit function #2 */
atexit(exit_fn2);
函数名: atof
功 能: 把字符串转换成浮点数
用 法: double atof(const char *nptr);
#include ;
#include ;
int main(void)
char *str = "12345.67";
f = atof(str);
printf("string = %s float = %f\n", str, f);
函数名: atoi
功 能: 把字符串转换成长整型数
用 法: int atoi(const char *nptr);
#include ;
#include ;
int main(void)
char *str = "12345.67";
n = atoi(str);
printf("string = %s integer = %d\n", str, n);
函数名: atol
功 能: 把字符串转换成长整型数
用 法: long atol(const char *nptr);
#include ;
#include ;
int main(void)
char *str = "";
l = atol(lstr);
printf("string = %s integer = %ld\n", str, l);
return(0);
函数名: bar
功 能: 画一个二维条形图
用 法: void far bar(int left, int top, int right, int bottom);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
int midx, midy,
/* 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:");
exit(1); /* terminate with an error code */
midx = getmaxx() / 2;
midy = getmaxy() / 2;
/* loop through the fill patterns */
for (i=SOLID_FILL; i<USER_FILL; i++)
/* set the fill style */
setfillstyle(i, getmaxcolor());
/* draw the bar */
bar(midx-50, midy-50, midx+50,
/* clean up */
closegraph();
函数名: bar3d
功 能: 画一个三维条形图
用 法: void far bar3d(int left, int top, int right, int bottom,
int depth, int topflag);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
int midx, midy,
/* 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:");
exit(1); /* terminate with error code */
midx = getmaxx() / 2;
midy = getmaxy() / 2;
/* loop through the fill patterns */
for (i=EMPTY_FILL; i<USER_FILL; i++)
/* set the fill style */
setfillstyle(i, getmaxcolor());
/* draw the 3-d bar */
bar3d(midx-50, midy-50, midx+50, midy+50, 10, 1);
/* clean up */
closegraph();
函数名: bdos
功 能: DOS系统调用
用 法: int bdos(int dosfun, unsigned dosdx, unsigned dosal);
#include ;
#include ;
/* Get current drive as 'A', 'B', ... */
char current_drive(void)
/* Get current disk as 0, 1, ... */
curdrive = bdos(0x19, 0, 0);
return('A' + curdrive);
int main(void)
printf("The current drive is %c:\n", current_drive());
函数名: bdosptr
功 能: DOS系统调用
用 法: int bdosptr(int dosfun, void *argument, unsigned dosal);
#include ;
#include ;
#include ;
#include ;
#include ;
#include ;
#define BUFLEN 80
int main(void)
char buffer[BUFLEN];
printf("Enter full pathname of a directory\n");
gets(buffer);
test = bdosptr(0x3B,buffer,0);
printf("DOS error message: %d\n", errno);
/* See errno.h for error listings */
getcwd(buffer, BUFLEN);
printf("The current directory is: %s\n", buffer);
函数名: bioscom
功 能: 串行I/O通信
用 法: int bioscom(int cmd, char abyte, int port);
#include ;
#include ;
#define COM1 0
#define DATA_READY 0x100
#define TRUE 1
#define FALSE 0
#define SETTINGS ( 0x80 | 0x02 | 0x00 | 0x00)
int main(void)
int in, out, status, DONE = FALSE;
bioscom(0, SETTINGS, COM1);
cprintf("... BIOSCOM [ESC] to exit ...\n");
while (!DONE)
status = bioscom(3, 0, COM1);
if (status & DATA_READY)
if ((out = bioscom(2, 0, COM1) & 0x7F) != 0)
putch(out);
if (kbhit())
if ((in = getch()) == '\x1B')
DONE = TRUE;
bioscom(1, in, COM1);
函数名: biosdisk
功 能: 软硬盘I/O
用 法: int biosdisk(int cmd, int drive, int head, int track, int sector
int nsects, void *buffer);
#include ;
#include ;
int main(void)
char buffer[512];
printf("Testing to see if drive a: is ready\n");
result = biosdisk(4,0,0,0,0,1,buffer);
result &= 0x02;
(result) ? (printf("Drive A: Ready\n")) :
(printf("Drive A: Not Ready\n"));
函数名: biosequip
功 能: 检查设备
用 法: int biosequip(void);
#include ;
#include ;
int main(void)
char buffer[512];
printf("Testing to see if drive a: is ready\n");
result = biosdisk(4,0,0,0,0,1,buffer);
result &= 0x02;
(result) ? (printf("Drive A: Ready\n")) :
(printf("Drive A: Not Ready\n"));
函数名: bioskey
功 能: 直接使用BIOS服务的键盘接口
用 法: int bioskey(int cmd);
#include ;
#include ;
#include ;
#define RIGHT 0x01
#define LEFT 0x02
#define CTRL 0x04
#define ALT 0x08
int main(void)
/* function 1 returns 0 until a key is pressed */
while (bioskey(1) == 0);
/* function 0 returns the key that is waiting */
key = bioskey(0);
/* use function 2 to determine if shift keys were used */
modifiers = bioskey(2);
if (modifiers)
printf("[");
if (modifiers & RIGHT) printf("RIGHT");
if (modifiers & LEFT) printf("LEFT");
if (modifiers & CTRL) printf("CTRL");
if (modifiers & ALT) printf("ALT");
printf("]");
/* print out the character read */
if (isalnum(key & 0xFF))
printf("'%c'\n", key);
printf("%#02x\n", key);
函数名: biosmemory
功 能: 返回存储块大小
用 法:int biosmemory(void);
#include ;
#include ;
int main(void)
int memory_
memory_size = biosmemory(); /* returns value up to 640K */
printf("RAM size = %dK\n",memory_size);
函数名: biosprint
功 能: 直接使用BIOS服务的打印机I/O
用 法: int biosprint(int cmd, int byte, int port);
#include ;
#include ;
#include ;
int main(void)
#define STATUS 2 /* printer status command */
#define PORTNUM 0 /* port number for LPT1 */
int status, abyte=0;
printf("Please turn off your printer. Press any key to continue\n");
status = biosprint(STATUS, abyte, PORTNUM);
if (status & 0x01)
printf("Device time out.\n");
if (status & 0x08)
printf("I/O error.\n");
if (status & 0x10)
printf("Selected.\n");
if (status & 0x20)
printf("Out of paper.\n");
if (status & 0x40)
printf("Acknowledge.\n");
if (status & 0x80)
printf("Not busy.\n");
函数名: biostime
功 能: 读取或设置BIOS时间
用 法: long biostime(int cmd, long newtime);
#include ;
#include ;
#include ;
#include ;
int main(void)
long bios_
cprintf("The number of clock ticks since midnight is:\r\n");
cprintf("The number of seconds since midnight is:\r\n");
cprintf("The number of minutes since midnight is:\r\n");
cprintf("The number of hours since midnight is:\r\n");
cprintf("\r\nPress any key to quit:");
while(!kbhit())
bios_time = biostime(0, 0L);
gotoxy(50, 1);
cprintf("%lu", bios_time);
gotoxy(50, 2);
cprintf("%.4f", bios_time / CLK_TCK);
gotoxy(50, 3);
cprintf("%.4f", bios_time / CLK_TCK / 60);
gotoxy(50, 4);
cprintf("%.4f", bios_time / CLK_TCK / 3600);
函数名: brk
功 能: 改变数据段空间分配
用 法: int brk(void *endds);
#include ;
#include ;
int main(void)
printf("Changing allocation with brk()\n");
ptr = malloc(1);
printf("Before brk() call: %lu bytes free\n", coreleft());
brk(ptr+1000);
printf(" After brk() call: %lu bytes free\n", coreleft());
函数名: bsearch
功 能: 二分法搜索
用 法: void *bsearch(const void *key, const void *base, size_t *nelem,
size_t width, int(*fcmp)(const void *, const *));
#include ;
#include ;
#define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))
int numarray[] = {123, 145, 512, 627, 800, 933};
int numeric (const int *p1, const int *p2)
return(*p1 - *p2);
int lookup(int key)
/* The cast of (int(*)(const void *,const void*))
is needed to avoid a type mismatch error at
compile time */
itemptr = bsearch (&key, numarray, NELEMS(numarray),
sizeof(int), (int(*)(const void *,const void *))numeric);
return (itemptr != NULL);
int main(void)
if (lookup(512))
printf("512 is in the table.\n");
printf("512 isn't in the table.\n");
函数名: cabs
功 能: 计算复数的绝对值
用 法: double cabs(struct complex z);
#include ;
#include ;
int main(void)
z.x = 2.0;
z.y = 1.0;
val = cabs(z);
printf("The absolute value of %.2lfi %.2lfj is %.2lf", z.x, z.y, val);
函数名: calloc
功 能: 分配主存储器
用 法: void *calloc(size_t nelem, size_t elsize);
#include ;
#include ;
int main(void)
char *str = NULL;
/* allocate memory for string */
str = calloc(10, sizeof(char));
/* copy "Hello" into string */
strcpy(str, "Hello");
/* display string */
printf("String is %s\n", str);
/* free memory */
free(str);
函数名: ceil
功 能: 向上舍入
用 法: double ceil(double x);
#include ;
#include ;
int main(void)
double number = 123.54;
double down,
down = floor(number);
up = ceil(number);
printf("original number %5.2lf\n", number);
printf("number rounded down %5.2lf\n", down);
printf("number rounded up %5.2lf\n", up);
函数名: cgets
功 能: 从控制台读字符串
用 法: char *cgets(char *str);
#include ;
#include ;
int main(void)
char buffer[83];
/* There's space for 80 characters plus the NULL terminator */
buffer[0] = 81;
printf("Input some chars:");
p = cgets(buffer);
printf("\ncgets read %d characters: \"%s\"\n", buffer[1], p);
printf("The returned pointer is %p, buffer[0] is at %p\n", p, &buffer);
/* Leave room for 5 characters plus the NULL terminator */
buffer[0] = 6;
printf("Input some chars:");
p = cgets(buffer);
printf("\ncgets read %d characters: \"%s\"\n", buffer[1], p);
printf("The returned pointer is %p, buffer[0] is at %p\n", p, &buffer);
函数名: chdir
功 能: 改变工作目录
用 法: int chdir(const char *path);
#include ;
#include ;
#include ;
char old_dir[MAXDIR];
char new_dir[MAXDIR];
int main(void)
if (getcurdir(0, old_dir))
perror("getcurdir()");
printf("Current directory is: \\%s\n", old_dir);
if (chdir("\\"))
perror("chdir()");
if (getcurdir(0, new_dir))
perror("getcurdir()");
printf("Current directory is now: \\%s\n", new_dir);
printf("\nChanging back to orignal directory: \\%s\n", old_dir);
if (chdir(old_dir))
perror("chdir()");
函数名: _chmod, chmod
功 能: 改变文件的访问方式
用 法: int chmod(const char *filename, int permiss);
#include ;
#include ;
#include ;
void make_read_only(char *filename);
int main(void)
make_read_only("NOTEXIST.FIL");
make_read_only("MYFILE.FIL");
void make_read_only(char *filename)
stat = chmod(filename, S_IREAD);
printf("Couldn't make %s read-only\n", filename);
printf("Made %s read-only\n", filename);
函数名: chsize
功 能: 改变文件大小
用 法: int chsize(int handle, long size);
#include ;
#include ;
#include ;
int main(void)
char buf[11] = "";
/* create text file containing 10 bytes */
handle = open("DUMMY.FIL", O_CREAT);
write(handle, buf, strlen(buf));
/* truncate the file to 5 bytes in size */
chsize(handle, 5);
/* close the file */
close(handle);
函数名: circle
功 能: 在给定半径以(x, y)为圆心画圆
用 法: void far circle(int x, int y, int radius);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
int 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:");
exit(1); /* terminate with an error code */
midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());
/* draw the circle */
circle(midx, midy, radius);
/* clean up */
closegraph();
函数名: cleardevice
功 能: 清除图形屏幕
用 法: void far cleardevice(void);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
/* 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:");
exit(1); /* terminate with an error code */
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 */
/* clear the screen */
cleardevice();
/* output another message */
outtextxy(midx, midy, "press any key to quit:");
/* clean up */
closegraph();
函数名: clearerr
功 能: 复位错误标志
用 法:void clearerr(FILE *stream);
#include ;
int main(void)
/* 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);
函数名: clearviewport
功 能: 清除图形视区
用 法: void far clearviewport(void);
#include ;
#include ;
#include ;
#include ;
#define CLIP_ON 1 /* activates clipping in viewport */
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
/* 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:");
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 */
/* clear the viewport */
clearviewport();
/* output another message */
outtextxy(0, 0, "Press any key to quit:");
/* clean up */
closegraph();
函数名: _close, close
功 能: 关闭文件句柄
用 法: int close(int handle);
#include ;
#include ;
#include ;
#include ;
char buf[11] = "";
/* 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);
printf("Error opening file\n");
函数名: clock
功 能: 确定处理器时间
用 法: clock_t clock(void);
#include ;
#include ;
#include ;
int main(void)
clock_t start,
start = clock();
delay(2000);
end = clock();
printf("The time was: %f\n", (end - start) / CLK_TCK);
函数名: closegraph
功 能: 关闭图形系统
用 法: void far closegraph(void);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
/* 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:");
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 */
/* closes down the graphics system */
closegraph();
printf("We're now back in text mode.\n");
printf("Press any key to halt:");
函数名: clreol
功 能: 在文本窗口中清除字符到行末
用 法: void clreol(void);
#include ;
int main(void)
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);
函数名: clrscr
功 能: 清除文本模式窗口
用 法: void clrscr(void);
#include ;
int main(void)
for (i = 0; i < 20; i++)
cprintf("%d\r\n", i);
cprintf("\r\nPress any key to clear screen");
cprintf("The screen has been cleared!");
函数名: coreleft
功 能: 返回未使用内存的大小
用 法: unsigned coreleft(void);
#include ;
#include ;
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());
函数名: cos
功 能: 余弦函数
用 法: double cos(double x);
#include ;
#include ;
int main(void)
double x = 0.5;
result = cos(x);
printf("The cosine of %lf is %lf\n", x, result);
函数名: cosh
功 能: 双曲余弦函数
用 法: dluble cosh(double x);
#include ;
#include ;
int main(void)
double x = 0.5;
result = cosh(x);
printf("The hyperboic cosine of %lf is %lf\n", x, result);
函数名: country
功 能: 返回与国家有关的信息
用 法: struct COUNTRY *country(int countrycode, struct country *country);
#include ;
#include ;
#define USA 0
int main(void)
struct COUNTRY country_
country(USA, &country_info);
printf("The currency symbol for the USA is: %s\n",
函数名: cprintf
功 能: 送格式化输出至屏幕
用 法: int cprintf(const char *format[, argument, ...]);
#include ;
int main(void)
/* clear the screen */
/* create a text window */
window(10, 10, 80, 25);
/* output some text in the window */
cprintf("Hello world\r\n");
/* wait for a key */
函数名: cputs
功 能: 写字符到屏幕
用 法: void cputs(const char *string);
#include ;
int main(void)
/* clear the screen */
/* 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 */
函数名: _creat creat
功 能: 创建一个新文件或重写一个已存在的文件
用 法: int creat (const char *filename, int permiss);
#include ;
#include ;
#include ;
#include ;
int main(void)
char buf[11] = "";
/* 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);
函数名: creatnew
功 能: 创建一个新文件
用 法: int creatnew(const char *filename, int attrib);
#include ;
#include ;
#include ;
#include ;
#include ;
int main(void)
char buf[11] = "";
/* attempt to create a file that doesn't already exist */
handle = creatnew("DUMMY.FIL", 0);
if (handle == -1)
printf("DUMMY.FIL already exists.\n");
printf("DUMMY.FIL successfully created.\n");
write(handle, buf, strlen(buf));
close(handle);
函数名: creattemp
功 能: 创建一个新文件或重写一个已存在的文件
用 法: int creattemp(const char *filename, int attrib);
#include ;
#include ;
#include ;
int main(void)
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);
函数名: cscanf
功 能: 从控制台执行格式化输入
用 法: int cscanf(char *format[,argument, ...]);
#include ;
int main(void)
char string[80];
/* clear the screen */
/* 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);
函数名: ctime
功 能: 把日期和时间转换为字符串
用 法: char *ctime(const time_t *time);
#include ;
#include ;
int main(void)
printf("Today's date and time: %s\n", ctime(&t));
函数名: ctrlbrk
功 能: 设置Ctrl-Break处理程序
用 法: void ctrlbrk(*fptr)(void);
#include ;
#include ;
#define ABORT 0
int c_break(void)
printf("Control-Break pressed. Program aborting ...\n");
return (ABORT);
int main(void)
ctrlbrk(c_break);
printf("Looping... Press ; to quit:\n");
函数名: delay
功 能: 将程序的执行暂停一段时间(毫秒)
用 法: void delay(unsigned milliseconds);
/* Emits a 440-Hz tone for 500 milliseconds */
#include ;
int main(void)
sound(440);
delay(500);
nosound();
函数名: delline
功 能: 在文本窗口中删去一行
用 法: void delline(void);
#include ;
int main(void)
cprintf("The function DELLINE deletes \
the line containing the\r\n");
cprintf("cursor and moves all lines \
below it one line up.\r\n");
cprintf("DELLINE operates within the \
currently active text\r\n");
cprintf("window. Press any key to \
continue . . .");
gotoxy(1,2); /* Move the cursor to the
second line and first column */
delline();
函数名: detectgraph
功 能: 通过检测硬件确定图形驱动程序和模式
用 法: void far detectgraph(int far *graphdriver, int far *graphmode);
#include ;
#include ;
#include ;
#include ;
/* names of the various cards supported */
char *dname[] = { "requests detection",
"an MCGA",
"a 64K EGA",
"a monochrome EGA",
"an IBM 8514",
"a Hercules monochrome",
"an AT&T 6300 PC",
"an IBM 3270 PC"
int main(void)
/* returns detected hardware info. */
int gdriver, gmode,
/* detect graphics hardware available */
detectgraph(&gdriver, &gmode);
/* read result of detectgraph call */
errorcode = graphresult();
if (errorcode != grOk) /* an error
occurred */
printf("Graphics error: %s\n", \
grapherrormsg(errorcode));
printf("Press any key to halt:");
exit(1); /* terminate with an error
/* display the information detected */
printf("You have %s video display \
card.\n", dname[gdriver]);
printf("Press any key to halt:");
函数名: difftime
功 能: 计算两个时刻之间的时间差
用 法: double difftime(time_t time2, time_t time1);
#include ;
#include ;
#include ;
#include ;
int main(void)
time_t first,
first = time(NULL); /* Gets system
delay(2000); /* Waits 2 secs */
second = time(NULL); /* Gets system time
printf("The difference is: %f \
seconds\n",difftime(second,first));
函数名: disable
功 能: 屏蔽中断
用 法: void disable(void);
/***NOTE: This is an interrupt service
routine. You cannot compile this program
with Test Stack Overflow turned on and
get an executable file that operates
correctly. */
#include ;
#include ;
#include ;
#define INTR 0X1C /* The clock tick
interrupt */
void interrupt ( *oldhandler)(void);
int count=0;
void interrupt handler(void)
/* disable interrupts during the handling of
the interrupt */
disable();
/* increase the global counter */
/* reenable interrupts at the end of the
handler */
/* 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);
函数名: div
功 能: 将两个整数相除, 返回商和余数
用 法: div_t (int number, int denom);
#include ;
#include ;
int main(void)
x = div(10,3);
printf("10 div 3 = %d remainder %d\n", x.quot, x.rem);
函数名: dosexterr
功 能: 获取扩展DOS错误信息
用 法: int dosexterr(struct DOSERR *dblkp);
#include ;
#include ;
int main(void)
struct DOSERROR
fp = fopen("perror.dat","r");
if (!fp) perror("Unable to open file for
reading");
dosexterr(&info);
printf("Extended DOS error \
information:\n");
printf(" Extended error: \
%d\n",info.exterror);
printf(" Class: \
%x\n",info.class);
printf(" Action: \
%x\n",info.action);
printf(" Error Locus: \
%x\n",info.locus);
函数名: dostounix
功 能: 转换日期和时间为UNIX时间格式
用 法: long dostounix(struct date *dateptr, struct time *timeptr);
#include ;
#include ;
#include ;
#include ;
int main(void)
struct time d_
struct date d_
struct tm *
getdate(&d_date);
gettime(&d_time);
t = dostounix(&d_date, &d_time);
local = localtime(&t);
printf("Time and Date: %s\n", \
asctime(local));
函数名: drawpoly
功 能: 画多边形
用 法: void far drawpoly(int numpoints, int far *polypoints);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
/* our polygon array */
int poly[10];
/* 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:");
/* terminate with an error code */
maxx = getmaxx();
maxy = getmaxy();
poly[0] = 20; /* 1st vertext */
poly[1] = maxy / 2;
poly[2] = maxx - 20; /* 2nd */
poly[3] = 20;
poly[4] = maxx - 50; /* 3rd */
poly[5] = maxy - 20;
poly[6] = maxx / 2; /* 4th */
poly[7] = maxy / 2;
drawpoly doesn't automatically close
the polygon, so we close it.
poly[8] = poly[0];
poly[9] = poly[1];
/* draw the polygon */
drawpoly(5, poly);
/* clean up */
closegraph();
函数名: dup
功 能: 复制一个文件句柄
用 法: int dup(int handle);
#include ;
#include ;
#include ;
#include ;
void flush(FILE *stream);
int main(void)
char msg[] = "This is a test";
/* create a file */
fp = fopen("DUMMY.FIL", "w");
/* write some data to the file */
fwrite(msg, strlen(msg), 1, fp);
printf("Press any key to flush \
DUMMY.FIL:");
/* flush the data to DUMMY.FIL without
closing it */
flush(fp);
printf("\nFile was flushed, Press any \
key to quit:");
void flush(FILE *stream)
/* flush TC's internal buffer */
fflush(stream);
/* make a duplicate file handle */
duphandle = dup(fileno(stream));
/* close the duplicate handle to flush the
DOS buffer */
close(duphandle);
函数名: dup2
功 能: 复制文件句柄
用 法: int dup2(int oldhandle, int newhandle);
#include ;
#include ;
#include ;
#include ;
int main(void)
#define STDOUT 1
char msg[] = "This is a test";
/* create a file */
nul = open("DUMMY.FIL", O_CREAT | O_RDWR,
S_IREAD | S_IWRITE);
/* create a duplicate handle for standard
oldstdout = dup(STDOUT);
redirect standard output to DUMMY.FIL
by duplicating the file handle onto the
file handle for standard output.
dup2(nul, STDOUT);
/* close the handle for DUMMY.FIL */
close(nul);
/* will be redirected into DUMMY.FIL */
write(STDOUT, msg, strlen(msg));
/* restore original standard output
dup2(oldstdout, STDOUT);
/* close duplicate handle for STDOUT */
close(oldstdout);
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);
#include ;
#include ;
#include ;
int main(void)
int ndig = 10;
value = 9.876;
string = ecvt(value, ndig, &dec, &sign);
printf("string = %s dec = %d \
sign = %d\n", string, dec, sign);
value = -123.45;
string = ecvt(value,ndig,&dec,&sign);
printf("string = %s dec = %d sign = %d\n",
string, dec, sign);
value = 0.6789e5; /* scientific
notation */
string = ecvt(value,ndig,&dec,&sign);
printf("string = %s dec = %d\
sign = %d\n", string, dec, sign);
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);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
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:");
/* terminate with an error code */
midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());
/* draw ellipse */
ellipse(midx, midy, stangle, endangle,
xradius, yradius);
/* clean up */
closegraph();
函数名: enable
功 能: 开放硬件中断
用 法: void enable(void);
/* ** 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 */
re enable interrupts at the end of the handler
/* 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);
函数名: eof
功 能: 检测文件结束
用 法: int eof(int *handle);
#include ;
#include ;
#include ;
#include ;
#include ;
int main(void)
char msg[] = "This is a test";
/* 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
read(handle, &ch, 1);
printf("%c", ch);
} while (!eof(handle));
close(handle);
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[]);
/* execv example */
#include ;
#include ;
#include ;
void main(int argc, char *argv[])
printf("Command line arguments:\n");
for (i=0; i< i++)
printf("[%2d] : %s\n", i, argv);
printf("About to exec child with arg1 arg2 ...\n");
execv("CHILD.EXE", argv);
perror("exec error");
函数名: exit
功 能: 终止程序
用 法: void exit(int status);
#include ;
#include ;
#include ;
int main(void)
printf("Enter either 1 or 2\n");
status = getch();
/* Sets DOS errorlevel */
exit(status - '0');
/* Note: this line is never reached */
函数名: exp
功 能: 指数函数
用 法: double exp(double x);
#include ;
#include ;
int main(void)
double x = 4.0;
result = exp(x);
printf("'e' raised to the power \
of %lf (e ^ %lf) = %lf\n",
x, x, result);
作者: hfh08&发布日期:
函数名: exp
功 能: 指数函数
用 法: double exp(double x);
#include ;
#include ;
int main(void)
double x = 4.0;
result = exp(x);
printf("'e' raised to the power \
of %lf (e ^ %lf) = %lf\n",
x, x, result);
函数名: fabs
功 能: 返回浮点数的绝对值
用 法: double fabs(double x);
#include ;
#include ;
int main(void)
float number = -1234.0;
printf("number: %f absolute value: %f\n",
number, fabs(number));
函数名: farcalloc
功 能: 从远堆栈中申请空间
用 法: void far *farcalloc(unsigned long units, unsigned ling unitsz);
#include ;
#include ;
#include ;
#include ;
int main(void)
char far *
char *str = "Hello";
/* allocate memory for the far pointer */
fptr = farcalloc(10, sizeof(char));
/* copy "Hello" into allocated memory */
Note: movedata is used because you
might be in a small data model, in
which case a normal string copy routine
can not be used since it assumes the
pointer size is near.
movedata(FP_SEG(str), FP_OFF(str),
FP_SEG(fptr), FP_OFF(fptr),
strlen(str));
/* display string (note the F modifier) */
printf("Far string is: %Fs\n", fptr);
/* free the memory */
farfree(fptr);
函数名: farcoreleft
功 能: 返回远堆中未作用存储区大小
用 法: long farcoreleft(void);
#include ;
#include ;
int main(void)
printf("The difference between the\
highest allocated block in the\
printf("heap and the top of the far heap\
is: %lu bytes\n", farcoreleft());
函数名: farfree
功 能: 从远堆中释放一块
用 法: void farfree(void);
#include ;
#include ;
#include ;
#include ;
int main(void)
char far *
char *str = "Hello";
/* allocate memory for the far pointer */
fptr = farcalloc(10, sizeof(char));
/* copy "Hello" into allocated memory */
Note: movedata is used because you might be in a small data model,
in which case a normal string copy routine can't be used since it
assumes the pointer size is near.
movedata(FP_SEG(str), FP_OFF(str),
FP_SEG(fptr), FP_OFF(fptr),
strlen(str));
/* display string (note the F modifier) */
printf("Far string is: %Fs\n", fptr);
/* free the memory */
farfree(fptr);
函数名: farmalloc
功 能: 从远堆中分配存储块
用 法: void far *farmalloc(unsigned long size);
#include ;
#include ;
#include ;
#include ;
int main(void)
char far *
char *str = "Hello";
/* allocate memory for the far pointer */
fptr = farmalloc(10);
/* copy "Hello" into allocated memory */
Note: movedata is used because we might
be in a small data model, in which case
a normal string copy routine can not be
used since it assumes the pointer size
movedata(FP_SEG(str), FP_OFF(str),
FP_SEG(fptr), FP_OFF(fptr),
strlen(str));
/* display string (note the F modifier) */
printf("Far string is: %Fs\n", fptr);
/* free the memory */
farfree(fptr);
函数名: farrealloc
功 能: 调整远堆中的分配块
用 法: void far *farrealloc(void far *block, unsigned long newsize);
#include ;
#include ;
int main(void)
char far *
fptr = farmalloc(10);
printf("First address: %Fp\n", fptr);
fptr = farrealloc(fptr,20);
printf("New address : %Fp\n", fptr);
farfree(fptr);
函数名: fclose
功 能: 关闭一个流
用 法: int fclose(FILE *stream);
#include ;
#include ;
int main(void)
char buf[11] = "";
/* create a file containing 10 bytes */
fp = fopen("DUMMY.FIL", "w");
fwrite(&buf, strlen(buf), 1, fp);
/* close the file */
fclose(fp);
函数名: fcloseall
功 能: 关闭打开流
用 法: int fcloseall(void);
#include ;
int main(void)
int streams_
/* open two streams */
fopen("DUMMY.ONE", "w");
fopen("DUMMY.TWO", "w");
/* close the open streams */
streams_closed = fcloseall();
if (streams_closed == EOF)
/* issue an error message */
perror("Error");
/* print result of fcloseall() function */
printf("%d streams were closed.\n", streams_closed);
函数名: fcvt
功 能: 把一个浮点数转换为字符串
用 法: char *fcvt(double value, int ndigit, int *decpt, int *sign);
#include ;
#include ;
#include ;
int main(void)
int ndig = 10;
value = 9.876;
string = ecvt(value, ndig, &dec, &sign);
printf("string = %s dec = %d \
sign = %d\n", string, dec, sign);
value = -123.45;
string = ecvt(value,ndig,&dec,&sign);
printf("string = %s dec = %d sign = %d\n",
string, dec, sign);
value = 0.6789e5; /* scientific
notation */
string = ecvt(value,ndig,&dec,&sign);
printf("string = %s dec = %d\
sign = %d\n", string, dec, sign);
函数名: fdopen
功 能: 把流与一个文件句柄相接
用 法: FILE *fdopen(int handle, char *type);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* open a file */
handle = open("DUMMY.FIL", O_CREAT,
S_IREAD | S_IWRITE);
/* now turn the handle into a stream */
stream = fdopen(handle, "w");
if (stream == NULL)
printf("fdopen failed\n");
fprintf(stream, "Hello world\n");
fclose(stream);
函数名: feof
功 能: 检测流上的文件结束符
用 法: int feof(FILE *stream);
#include ;
int main(void)
/* open a file for reading */
stream = fopen("DUMMY.FIL", "r");
/* read a character from the file */
fgetc(stream);
/* check for EOF */
if (feof(stream))
printf("We have reached end-of-file\n");
/* close the file */
fclose(stream);
函数名: ferror
功 能: 检测流上的错误
用 法: int ferror(FILE *stream);
#include ;
int main(void)
/* open a file for writing */
stream = fopen("DUMMY.FIL", "w");
/* force an error condition by attempting to read */
(void) getc(stream);
if (ferror(stream)) /* test for an error on the stream */
/* display an error message */
printf("Error reading from DUMMY.FIL\n");
/* reset the error and EOF indicators */
clearerr(stream);
fclose(stream);
函数名: fflush
功 能: 清除一个流
用 法: int fflush(FILE *stream);
#include ;
#include ;
#include ;
#include ;
void flush(FILE *stream);
int main(void)
char msg[] = "This is a test";
/* create a file */
stream = fopen("DUMMY.FIL", "w");
/* write some data to the file */
fwrite(msg, strlen(msg), 1, stream);
printf("Press any key to flush\
DUMMY.FIL:");
/* flush the data to DUMMY.FIL without\
closing it */
flush(stream);
printf("\nFile was flushed, Press any key\
to quit:");
void flush(FILE *stream)
/* flush the stream's internal buffer */
fflush(stream);
/* make a duplicate file handle */
duphandle = dup(fileno(stream));
/* close the duplicate handle to flush\
the DOS buffer */
close(duphandle);
函数名: fgetc
功 能: 从流中读取字符
用 法: int fgetc(FILE *stream);
#include ;
#include ;
#include ;
int main(void)
char string[] = "This is a test";
/* open a file for update */
stream = fopen("DUMMY.FIL", "w+");
/* write a string into the file */
fwrite(string, strlen(string), 1, stream);
/* seek to the beginning of the file */
fseek(stream, 0, SEEK_SET);
/* read a char from the file */
ch = fgetc(stream);
/* display the character */
putch(ch);
} while (ch != EOF);
fclose(stream);
函数名: fgetchar
功 能: 从流中读取字符
用 法: int fgetchar(void);
#include ;
int main(void)
/* prompt the user for input */
printf("Enter a character followed by \
/* read the character from stdin */
ch = fgetchar();
/* display what was read */
printf("The character read is: '%c'\n",
函数名: fgetpos
功 能: 取得当前文件的句柄
用 法: int fgetpos(FILE *stream);
#include ;
#include ;
int main(void)
char string[] = "This is a test";
/* open a file for update */
stream = fopen("DUMMY.FIL", "w+");
/* write a string into the file */
fwrite(string, strlen(string), 1, stream);
/* report the file pointer position */
fgetpos(stream, &filepos);
printf("The file pointer is at byte\
%ld\n", filepos);
fclose(stream);
函数名: fgets
功 能: 从流中读取一字符串
用 法: char *fgets(char *string, int n, FILE *stream);
#include ;
#include ;
int main(void)
char string[] = "This is a test";
char msg[20];
/* open a file for update */
stream = fopen("DUMMY.FIL", "w+");
/* write a string into the file */
fwrite(string, strlen(string), 1, stream);
/* seek to the start of the file */
fseek(stream, 0, SEEK_SET);
/* read a string from the file */
fgets(msg, strlen(string)+1, stream);
/* display the string */
printf("%s", msg);
fclose(stream);
函数名: filelength
功 能: 取文件长度字节数
用 法: long filelength(int handle);
#include ;
#include ;
#include ;
#include ;
int main(void)
char buf[11] = "";
/* create a file containing 10 bytes */
handle = open("DUMMY.FIL", O_CREAT);
write(handle, buf, strlen(buf));
/* display the size of the file */
printf("file length in bytes: %ld\n",
filelength(handle));
/* close the file */
close(handle);
函数名: fillellipse
功 能: 画出并填充一椭圆
用 法: void far fillellipse(int x, int y, int xradius, int yradius);
#include ;
#include ;
int main(void)
int gdriver = DETECT,
int xcenter, ycenter,
initgraph(&gdriver,&gmode,"");
xcenter = getmaxx() / 2;
ycenter = getmaxy() / 2;
for (i=0; i<13; i++)
setfillstyle(i,WHITE);
fillellipse(xcenter,ycenter,100,50);
closegraph();
函数名: fillpoly
功 能: 画并填充一个多边形
用 法: void far fillpoly(int numpoints, int far *polypoints);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
int i, maxx,
/* our polygon array */
int poly[8];
/* 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:");
/* terminate with an error code */
maxx = getmaxx();
maxy = getmaxy();
poly[0] = 20; /* 1st vertext */
poly[1] = maxy / 2;
poly[2] = maxx - 20; /* 2nd */
poly[3] = 20;
poly[4] = maxx - 50; /* 3rd */
poly[5] = maxy - 20;
4th vertex. fillpoly automatically
closes the polygon.
poly[6] = maxx / 2;
poly[7] = maxy / 2;
/* loop through the fill patterns */
for (i=EMPTY_FILL; i<USER_FILL; i++)
/* set fill pattern */
setfillstyle(i, getmaxcolor());
/* draw a filled polygon */
fillpoly(4, poly);
/* clean up */
closegraph();
函数名: findfirst, findnext
功 能: 搜索磁盘目录; 取得下一个匹配的findfirst模式的文件
用 法: int findfirst(char *pathname, struct ffblk *ffblk, int attrib);
int findnext(struct ffblk *ffblk);
/* findnext example */
#include ;
#include ;
int main(void)
printf("Directory listing of *.*\n");
done = findfirst("*.*",&ffblk,0);
while (!done)
printf(" %s\n", ffblk.ff_name);
done = findnext(&ffblk);
函数名: floodfill
功 能: 填充一个有界区域
用 法: void far floodfill(int x, int y, int border);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
/* 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:");
/* terminate with an error code */
maxx = getmaxx();
maxy = getmaxy();
/* select drawing color */
setcolor(getmaxcolor());
/* select fill color */
setfillstyle(SOLID_FILL, getmaxcolor());
/* draw a border around the screen */
rectangle(0, 0, maxx, maxy);
/* draw some circles */
circle(maxx / 3, maxy /2, 50);
circle(maxx / 2, 20, 100);
circle(maxx-20, maxy-50, 75);
circle(20, maxy-20, 25);
/* wait for a key */
/* fill in bounded region */
floodfill(2, 2, getmaxcolor());
/* clean up */
closegraph();
函数名: floor
功 能: 向下舍入
用 法: double floor(double x);
#include ;
#include ;
int main(void)
double number = 123.54;
double down,
down = floor(number);
up = ceil(number);
printf("original number %10.2lf\n",
printf("number rounded down %10.2lf\n",
printf("number rounded up %10.2lf\n",
函数名: flushall
功 能: 清除所有缓冲区
用 法: int flushall(void);
#include ;
int main(void)
/* create a file */
stream = fopen("DUMMY.FIL", "w");
/* flush all open streams */
printf("%d streams were flushed.\n",
flushall());
/* close the file */
fclose(stream);
函数名: fmod
功 能: 计算x对y的模, 即x/y的余数
用 法: double fmod(double x, double y);
#include ;
#include ;
int main(void)
double x = 5.0, y = 2.0;
result = fmod(x,y);
printf("The remainder of (%lf / %lf) is \
%lf\n", x, y, result);
函数名: fnmerge
功 能: 建立新文件名
用 法: void fnerge(char *path, char *drive, char *dir);
#include ;
#include ;
#include ;
int main(void)
char s[MAXPATH];
char drive[MAXDRIVE];
char dir[MAXDIR];
char file[MAXFILE];
char ext[MAXEXT];
getcwd(s,MAXPATH); /* get the current working directory */
strcat(s,"\\"); /* append on a trailing \ character */
fnsplit(s,drive,dir,file,ext); /* split the string to separate elems */
strcpy(file,"DATA");
strcpy(ext,".TXT");
fnmerge(s,drive,dir,file,ext); /* merge everything into one string */
puts(s); /* display resulting string */
函数名: fopen
功 能: 打开一个流
用 法: FILE *fopen(char *filename, char *type);
#include ;
#include ;
#include ;
int main(void)
char drive[MAXDRIVE];
char dir[MAXDIR];
char file[MAXFILE];
char ext[MAXEXT];
s=getenv("COMSPEC"); /* get the comspec environment parameter */
flags=fnsplit(s,drive,dir,file,ext);
printf("Command processor info:\n");
if(flags & DRIVE)
printf("\tdrive: %s\n",drive);
if(flags & DIRECTORY)
printf("\tdirectory: %s\n",dir);
if(flags & FILENAME)
printf("\tfile: %s\n",file);
if(flags & EXTENSION)
printf("\textension: %s\n",ext);
函数名: fprintf
功 能: 传送格式化输出到一个流中
用 法: int fprintf(FILE *stream, char *format[, argument,...]);
/* Program to create backup of the
AUTOEXEC.BAT file */
#include ;
int main(void)
FILE *in, *
if ((in = fopen("\\AUTOEXEC.BAT", "rt"))
fprintf(stderr, "Cannot open input \
file.\n");
if ((out = fopen("\\AUTOEXEC.BAK", "wt"))
fprintf(stderr, "Cannot open output \
file.\n");
while (!feof(in))
fputc(fgetc(in), out);
fclose(in);
fclose(out);
函数名: FP_OFF
功 能: 获取远地址偏移量
用 法: unsigned FP_OFF(void far *farptr);
/* FP_OFF */
#include ;
#include ;
int main(void)
char *str = "fpoff.c";
printf("The offset of this file in memory\
is: %Fp\n", FP_OFF(str));
函数名: FP_SEG
功 能: 获取远地址段值
用 法: unsigned FP_SEG(void far *farptr);
/* FP_SEG */
#include ;
#include ;
int main(void)
char *filename = "fpseg.c";
printf("The offset of this file in memory\
is: %Fp\n", FP_SEG(filename));
return(0);
函数名: fputc
功 能: 送一个字符到一个流中
用 法: int fputc(int ch, FILE *stream);
#include ;
int main(void)
char msg[] = "Hello world";
int i = 0;
while (msg)
fputc(msg, stdout);
函数名: fputchar
功 能: 送一个字符到标准输出流(stdout)中
用 法: int fputchar(char ch);
#include ;
int main(void)
char msg[] = "This is a test";
int i = 0;
while (msg)
fputchar(msg);
函数名: fputs
功 能: 送一个字符到一个流中
用 法: int fputs(char *string, FILE *stream);
#include ;
int main(void)
/* write a string to standard output */
fputs("Hello world\n", stdout);
函数名: fread
功 能: 从一个流中读数据
用 法: int fread(void *ptr, int size, int nitems, FILE *stream);
#include ;
#include ;
int main(void)
char msg[] = "this is a test";
char buf[20];
if ((stream = fopen("DUMMY.FIL", "w+"))
fprintf(stderr,
"Cannot open output file.\n");
/* write some data to the file */
fwrite(msg, strlen(msg)+1, 1, stream);
/* seek to the beginning of the file */
fseek(stream, SEEK_SET, 0);
/* read the data and display it */
fread(buf, strlen(msg)+1, 1, stream);
printf("%s\n", buf);
fclose(stream);
函数名: free
功 能: 释放已分配的块
用 法: void free(void *ptr);
#include ;
#include ;
#include ;
int main(void)
/* allocate memory for string */
str = malloc(10);
/* copy "Hello" to string */
strcpy(str, "Hello");
/* display string */
printf("String is %s\n", str);
/* free memory */
free(str);
函数名: freemem
功 能: 释放先前分配的DOS内存块
用 法: int freemem(unsigned seg);
#include ;
#include ;
#include ;
int main(void)
unsigned int size,
size = 64; /* (64 x 16) = 1024 bytes */
stat = allocmem(size, &segp);
if (stat < 0)
printf("Allocated memory at segment:\
%x\n", segp);
printf("Failed: maximum number of\
paragraphs available is %u\n",
freemem(segp);
函数名: freopen
功 能: 替换一个流
用 法: FILE *freopen(char *filename, char *type, FILE *stream);
#include ;
int main(void)
/* redirect standard output to a file */
if (freopen("OUTPUT.FIL", "w", stdout)
fprintf(stderr, "error redirecting\
stdout\n");
/* this output will go to a file */
printf("This will go into a file.");
/* close the standard output stream */
fclose(stdout);
函数名: frexp
功 能: 把一个双精度数分解为尾数的指数
用 法: double frexp(double value, int *eptr);
#include ;
#include ;
int main(void)
double mantissa,
number = 8.0;
mantissa = frexp(number, &exponent);
printf("The number %lf is ", number);
printf("%lf times two to the ", mantissa);
printf("power of %d\n", exponent);
函数名: fscanf
功 能: 从一个流中执行格式化输入
用 法: int fscanf(FILE *stream, char *format[,argument...]);
#include ;
#include ;
int main(void)
printf("Input an integer: ");
/* read an integer from the
standard input stream */
if (fscanf(stdin, "%d", &i))
printf("The integer read was: %i\n",
fprintf(stderr, "Error reading an \
integer from stdin.\n");
函数名: fseek
功 能: 重定位流上的文件指针
用 法: int fseek(FILE *stream, long offset, int fromwhere);
#include ;
long filesize(FILE *stream);
int main(void)
stream = fopen("MYFILE.TXT", "w+");
fprintf(stream, "This is a test");
printf("Filesize of MYFILE.TXT is %ld bytes\n", filesize(stream));
fclose(stream);
long filesize(FILE *stream)
long curpos,
curpos = ftell(stream);
fseek(stream, 0L, SEEK_END);
length = ftell(stream);
fseek(stream, curpos, SEEK_SET);
函数名: fsetpos
功 能: 定位流上的文件指针
用 法: int fsetpos(FILE *stream, const fpos_t *pos);
#include ;
#include ;
void showpos(FILE *stream);
int main(void)
/* open a file for update */
stream = fopen("DUMMY.FIL", "w+");
/* save the file pointer position */
fgetpos(stream, &filepos);
/* write some data to the file */
fprintf(stream, "This is a test");
/* show the current file position */
showpos(stream);
/* set a new file position, display it */
if (fsetpos(stream, &filepos) == 0)
showpos(stream);
fprintf(stderr, "Error setting file \
pointer.\n");
/* close the file */
fclose(stream);
void showpos(FILE *stream)
/* display the current file pointer
position of a stream */
fgetpos(stream, &pos);
printf("File position: %ld\n", pos);
函数名: fstat
功 能: 获取打开文件信息
用 法: int fstat(char *handle, struct stat *buff);
#include ;
#include ;
#include ;
int main(void)
/* open a file for update */
if ((stream = fopen("DUMMY.FIL", "w+"))
fprintf(stderr, "Cannot open output \
file.\n");
return(1);
fprintf(stream, "This is a test");
fflush(stream);
/* get information about the file */
fstat(fileno(stream), &statbuf);
fclose(stream);
/* display the information returned */
if (statbuf.st_mode & S_IFCHR)
printf("Handle refers to a device.\n");
if (statbuf.st_mode & S_IFREG)
printf("Handle refers to an ordinary \
file.\n");
if (statbuf.st_mode & S_IREAD)
printf("User has read permission on \
file.\n");
if (statbuf.st_mode & S_IWRITE)
printf("User has write permission on \
file.\n");
printf("Drive letter of file: %c\n",
'A'+statbuf.st_dev);
printf("Size of file in bytes: %ld\n",
statbuf.st_size);
printf("Time file last opened: %s\n",
ctime(&statbuf.st_ctime));
函数名: ftell
功 能: 返回当前文件指针
用 法: long ftell(FILE *stream);
#include ;
int main(void)
stream = fopen("MYFILE.TXT", "w+");
fprintf(stream, "This is a test");
printf("The file pointer is at byte \
%ld\n", ftell(stream));
fclose(stream);
函数名: fwrite
功 能: 写内容到流中
用 法: int fwrite(void *ptr, int size, int nitems, FILE *stream);
#include ;
struct mystruct
int main(void)
if ((stream = fopen("TEST.$$$", "wb")) == NULL) /* open file TEST.$$$ */
fprintf(stderr, "Cannot open output file.\n");
s.ch = 'A';
fwrite(&s, sizeof(s), 1, stream); /* write struct s to file */
fclose(stream); /* close file */
函数名: gcvt
功 能: 把浮点数转换成字符串
用 法: char *gcvt(double value, int ndigit, char *buf);
#include ;
#include ;
int main(void)
char str[25];
int sig = 5; /* significant digits */
/* a regular number */
num = 9.876;
gcvt(num, sig, str);
printf("string = %s\n", str);
/* a negative number */
num = -123.4567;
gcvt(num, sig, str);
printf("string = %s\n", str);
/* scientific notation */
num = 0.678e5;
gcvt(num, sig, str);
printf("string = %s\n", str);
return(0);
函数名: geninterrupt
功 能: 产生一个软中断
用 法: void geninterrupt(int intr_num);
#include ;
#include ;
/* function prototype */
void writechar(char ch);
int main(void)
gotoxy(80,25);
writechar('*');
outputs a character at the current cursor
position using the video BIOS to avoid the
scrolling of the screen when writing to
location (80,25).
void writechar(char ch)
struct text_
/* grab current text settings */
gettextinfo(&ti);
/* interrupt 0x10 sub-function 9 */
/* character to be output */
_BH = 0; /* video page */
_BL = ti. /* video attribute */
_CX = 1; /* repetition factor */
geninterrupt(0x10); /* output the char */
函数名: getarccoords
功 能: 取得最后一次调用arc的坐标
用 法: void far getarccoords(struct arccoordstype far *arccoords);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
int stangle = 45, endangle = 270;
char sstr[80], estr[80];
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
printf("Graphics error: %s\n",
grapherrormsg(errorcode));
printf("Press any key to halt:");
/* terminate with an error code */
midx = getmaxx() / 2;
midy = getmaxy() / 2;
/* draw arc and get coordinates */
setcolor(getmaxcolor());
arc(midx, midy, stangle, endangle, 100);
getarccoords(&arcinfo);
/* convert arc information into strings */
sprintf(sstr, "*- (%d, %d)",
arcinfo.xstart, arcinfo.ystart);
sprintf(estr, "*- (%d, %d)",
arcinfo.xend, arcinfo.yend);
/* output the arc information */
outtextxy(arcinfo.xstart,
arcinfo.ystart, sstr);
outtextxy(arcinfo.xend,
arcinfo.yend, estr);
/* clean up */
closegraph();
函数名: getaspectratio
功 能: 返回当前图形模式的纵横比
用 法: void far getaspectratio(int far *xasp, int far *yasp);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
int xasp, yasp, midx,
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
printf("Graphics error: %s\n",
grapherrormsg(errorcode));
printf("Press any key to halt:");
/* terminate with an error code */
midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());
/* get current aspect ratio settings */
getaspectratio(&xasp, &yasp);
/* draw normal circle */
circle(midx, midy, 100);
/* draw wide circle */
cleardevice();
setaspectratio(xasp/2, yasp);
circle(midx, midy, 100);
/* draw narrow circle */
cleardevice();
setaspectratio(xasp, yasp/2);
circle(midx, midy, 100);
/* clean up */
closegraph();
函数名: getbkcolor
功 能: 返回当前背景颜色
用 法: int far getbkcolor(void);
#include ;
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
int bkcolor, midx,
char bkname[35];
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
printf("Graphics error: %s\n",
grapherrormsg(errorcode));
printf("Press any key to halt:");
/* terminate with an error code */
midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());
/* for centering text on the display */
settextjustify(CENTER_TEXT, CENTER_TEXT);
/* get the current background color */
bkcolor = getbkcolor();
/* convert color value into a string */
itoa(bkcolor, bkname, 10);
strcat(bkname,
" is the current background color.");
/* display a message */
outtextxy(midx, midy, bkname);
/* clean up */
closegraph();
函数名: getc
功 能: 从流中取字符
用 法: int getc(FILE *stream);
#include ;
int main(void)
printf("Input a character:");
/* read a character from the
standard input stream */
ch = getc(stdin);
printf("The character input was: '%c'\n",
函数名: getcbrk
功 能: 获取Control_break设置
用 法: int getcbrk(void);
#include ;
#include ;
int main(void)
if (getcbrk())
printf("Cntrl-brk flag is on\n");
printf("Cntrl-brk flag is off\n");
函数名: getch
功 能: 从控制台无回显地取一个字符
用 法: int getch(void);
#include ;
#include ;
int main(void)
printf("Input a character:");
ch = getche();
printf("\nYou input a '%c'\n", ch);
函数名: getchar
功 能: 从stdin流中读字符
用 法: int getchar(void);
#include ;
int main(void)
/* Note that getchar reads from stdin and
this means it will
not return until you press ENTER. */
while ((c = getchar()) != '\n')
printf("%c", c);
函数名: getche
功 能: 从控制台取字符(带回显)
用 法: int getche(void);
#include ;
#include ;
int main(void)
printf("Input a character:");
ch = getche();
printf("\nYou input a '%c'\n", ch);
函数名: getcolor
功 能: 返回当前画线颜色
用 法: int far getcolor(void);
#include ;
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
int color, midx,
char colname[35];
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
printf("Graphics error: %s\n",
grapherrormsg(errorcode));
printf("Press any key to halt:");
/* terminate with an error code */
midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());
/* for centering text on the display */
settextjustify(CENTER_TEXT, CENTER_TEXT);
/* get the current drawing color */
color = getcolor();
/* convert color value into a string */
itoa(color, colname, 10);
strcat(colname,
" is the current drawing color.");
/* display a message */
outtextxy(midx, midy, colname);
/* clean up */
closegraph();
函数名: getcurdir
功 能: 取指定驱动器的当前目录
用 法: int getcurdir(int drive, char *direc);
#include ;
#include ;
#include ;
char *current_directory(char *path)
strcpy(path, "X:\\"); /* fill string with form of response: X:\ */
path[0] = 'A' + getdisk(); /* replace X with current drive letter */
getcurdir(0, path+3); /* fill rest of string with current directory */
return(path);
int main(void)
char curdir[MAXPATH];
current_directory(curdir);
printf("The current directory is %s\n", curdir);
函数名: getcwd
功 能: 取当前工作目录
用 法: char *getcwd(char *buf, int n);
#include ;
#include ;
int main(void)
char buffer[MAXPATH];
getcwd(buffer, MAXPATH);
printf("The current directory is: %s\n", buffer);
函数名: getdate
功 能: 取DOS日期
用 法: void getdate(struct *dateblk);
#include ;
#include ;
int main(void)
getdate(&d);
printf("The current year is: %d\n",
d.da_year);
printf("The current day is: %d\n",
d.da_day);
printf("The current month is: %d\n",
d.da_mon);
函数名: getdefaultpalette
功 能: 返回调色板定义结构
用 法: struct palettetype *far getdefaultpalette(void);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
/* structure for returning palette copy */
struct palettetype far *pal=(void *) 0;
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
printf("Graphics error: %s\n",
grapherrormsg(errorcode));
printf("Press any key to halt:");
/* terminate with an error code */
setcolor(getmaxcolor());
/* return a pointer to the default palette */
pal = getdefaultpalette();
for (i=0; i<16; i++)
printf("colors[%d] = %d\n", i,
pal->;colors);
/* clean up */
closegraph();
函数名: getdisk
功 能: 取当前磁盘驱动器号
用 法: int getdisk(void);
#include ;
#include ;
int main(void)
disk = getdisk() + 'A';
printf("The current drive is: %c\n",
函数名: getdrivername
功 能: 返回指向包含当前图形驱动程序名字的字符串指针
用 法: char *getdrivename(void);
#include ;
#include ;
#include ;
#include ;
int main(void)
/* request auto detection */
int gdriver = DETECT, gmode,
/* stores the device driver name */
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
printf("Graphics error: %s\n",
grapherrormsg(errorcode));
printf("Press any key to halt:");
/* terminate with an error code */
setcolor(getmaxcolor());
/* get name of the device driver i