C语言常用函数

C 语言常用函数 第 1 页 共 250 页 函数名 abort 功 能 异常终止一个进程 用 法 void abort void 程序例 include include int main void printf Calling abort n abort 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 程序例 include include int main void int number 1234 printf number d absolute value d n number abs number return 0 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 程序例 absread example include include include include int main void int i strt ch out sector char buf 512 printf Insert a diskette into drive A and press any key n getch sector 0 if absread 0 1 sector exit 1 C 语言常用函数 第 2 页 共 250 页 printf Read OK n strt 3 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 程序例 include include int file exists char filename int main void printf Does NOTEXIST FIL exist s n file exists NOTEXISTS FIL YES NO return 0 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 程序例 include include int main void double result double x 0 5 result acos x printf The arc cosine of lf is lf n x result return 0 C 语言常用函数 第 3 页 共 250 页 函数名 allocmem 功 能 分配 DOS 存储段 用 法 int allocmem unsigned size unsigned seg 程序例 include include include int main void unsigned int size segp int stat size 64 64 x 16 1024 bytes stat allocmem size if stat 1 printf Allocated memory at segment x n segp else printf Failed maximum number of paragraphs available is u n stat return 0 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 程序例 include include include include int main void request auto detection int gdriver DETECT gmode errorcode int midx midy int stangle 45 endangle 135 int radius 100 initialize graphics and local variables initgraph 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 getch C 语言常用函数 第 4 页 共 250 页 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 getch closegraph return 0 函数名 asctime 功 能 转换日期和时间为 ASCII 码 用 法 char asctime const struct tm tblock 程序例 include include include int main void struct tm t 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 SavTime does not show in asctime converts structure to null terminated string strcpy str asctime printf s n str return 0 函数名 asin 功 能 反正弦函数 用 法 double asin double x 程序例 include include C 语言常用函数 第 5 页 共 250 页 int main void double result 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 程序例 include include include struct ITEM int key int value 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 return 0 函数名 atan 功 能 反正切函数 用 法 double atan double x 程序例 include include int main void double result double x 0 5 result atan x printf The arc tangent of lf is lf n x result return 0 C 语言常用函数 第 6 页 共 250 页 函数名 atan2 功 能 计算 Y X 的反正切值 用 法 double atan2 double y double x 程序例 include include int main void double result double x 90 0 y 45 0 result atan2 y x printf The arc tangent ratio of lf is lf n y x result return 0 函数名 atexit 功 能 注册终止函数 用 法 int atexit atexit t func 程序例 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 return 0 函数名 atof 功 能 把字符串转换成浮点数 用 法 double atof const char nptr 程序例 include include int main void float f C 语言常用函数 第 7 页 共 250 页 char str 12345 67 f atof str printf string s float f n str f return 0 函数名 atoi 功 能 把字符串转换成长整型数 用 法 int atoi const char nptr 程序例 include include int main void int n char str 12345 67 n atoi str printf string s integer d n str n return 0 函数名 atol 功 能 把字符串转换成长整型数 用 法 long atol const char nptr 程序例 include include int main void long l char str 98765432 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 程序例 include include include include int main void request auto detection C 语言常用函数 第 8 页 共 250 页 int gdriver DETECT gmode errorcode int midx midy i initialize graphics and local variables initgraph 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 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 midy 50 getch clean up closegraph return 0 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 程序例 include include include include int main void C 语言常用函数 第 9 页 共 250 页 request auto detection int gdriver DETECT gmode errorcode int midx midy i initialize graphics local variables initgraph 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 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 getch clean up closegraph return 0 函数名 bdos 功 能 DOS 系统调用 用 法 int bdos int dosfun unsigned dosdx unsigned dosal 程序例 include include Get current drive as A B char current drive void char curdrive Get current disk as 0 1 curdrive bdos 0 x19 0 0 return A curdrive int main void C 语言常用函数 第 10 页 共 250 页 printf The current drive is c n current drive return 0 函数名 bdosptr 功 能 DOS 系统调用 用 法 int bdosptr int dosfun void argument unsigned dosal 程序例 include include include include include include define BUFLEN 80 int main void char buffer BUFLEN int test printf Enter full pathname of a directory n gets buffer test bdosptr 0 x3B buffer 0 if test printf DOS error message d n errno See errno h for error listings exit 1 getcwd buffer BUFLEN printf The current directory is s n buffer return 0 函数名 bioscom 功 能 串行 I O 通信 用 法 int bioscom int cmd char abyte int port 程序例 include include define COM1 0 define DATA READY 0 x100 define TRUE 1 define FALSE 0 define SETTINGS 0 x80 0 x02 0 x00 0 x00 int main void C 语言常用函数 第 11 页 共 250 页 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 if kbhit if in getch x1B DONE TRUE bioscom 1 in COM1 return 0 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 程序例 include include int main void int result char buffer 512 printf Testing to see if drive a is ready n result biosdisk 4 0 0 0 0 1 buffer result result printf Drive A Ready n printf Drive A Not Ready n return 0 函数名 biosequip 功 能 检查设备 用 法 int biosequip void 程序例 include include int main void int result C 语言常用函数 第 12 页 共 250 页 char buffer 512 printf Testing to see if drive a is ready n result biosdisk 4 0 0 0 0 1 buffer result result printf Drive A Ready n printf Drive A Not Ready n return 0 函数名 bioskey 功 能 直接使用 BIOS 服务的键盘接口 用 法 int bioskey int cmd 程序例 include include include define RIGHT 0 x01 define LEFT 0 x02 define CTRL 0 x04 define ALT 0 x08 int main void int key modifiers 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 if modifiers if modifiers if modifiers printf print out the character read if isalnum key else printf 02x n key return 0 C 语言常用函数 第 13 页 共 250 页 函数名 biosmemory 功 能 返回存储块大小 用 法 int biosmemory void 程序例 include include int main void int memory size memory size biosmemory returns value up to 640K printf RAM size dK n memory size return 0 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 程序例 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 getch status biosprint STATUS abyte PORTNUM if status if status if status if status if status if status return 0 C 语言常用函数 第 14 页 共 250 页 函数名 biostime 功 能 读取或设置 BIOS 时间 用 法 long biostime int cmd long newtime 程序例 include include include include int main void long bios time clrscr 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 return 0 函数名 brk 功 能 改变数据段空间分配 用 法 int brk void endds 程序例 include include int main void char ptr C 语言常用函数 第 15 页 共 250 页 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 return 0 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 程序例 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 int itemptr The cast of int const void const void is needed to avoid a type mismatch error at compile time itemptr bsearch return itemptr NULL int main void if lookup 512 printf 512 is in the table n else printf 512 isn t in the table n return 0 函数名 cabs 功 能 计算复数的绝对值 用 法 double cabs struct complex z C 语言常用函数 第 16 页 共 250 页 程序例 include include int main void struct complex z double val 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 return 0 函数名 calloc 功 能 分配主存储器 用 法 void calloc size t nelem size t elsize 程序例 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 return 0 函数名 ceil 功 能 向上舍入 用 法 double ceil double x 程序例 include include int main void double number 123 54 double down up down floor number up ceil number printf original number 5 2lf n number C 语言常用函数 第 17 页 共 250 页 printf number rounded down 5 2lf n down printf number rounded up 5 2lf n up return 0 函数名 cgets 功 能 从控制台读字符串 用 法 char cgets char str 程序例 include include int main void char buffer 83 char p 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 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 return 0 函数名 chdir 功 能 改变工作目录 用 法 int chdir const char path 程序例 include include include char old dir MAXDIR char new dir MAXDIR int main void if getcurdir 0 old dir perror getcurdir exit 1 printf Current directory is s n old dir C 语言常用函数 第 18 页 共 250 页 if chdir perror chdir exit 1 if getcurdir 0 new dir perror getcurdir exit 1 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 exit 1 return 0 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 程序例 include include include void make read only char filename int main void make read only NOTEXIST FIL make read only MYFILE FIL return 0 void make read only char filename int stat stat chmod filename S IREAD if stat printf Couldn t make s read only n filename else printf Made s read only n filename C 语言常用函数 第 19 页 共 250 页 函数名 chsize 功 能 改变文件大小 用 法 int chsize int handle long size 程序例 include include include int main void int handle char buf 11 0123456789 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 return 0 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 程序例 include include include include int main void request auto detection int gdriver DETECT gmode errorcode int midx midy int radius 100 initialize graphics and local variables initgraph 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 C 语言常用函数 第 20 页 共 250 页 midx getmaxx 2 midy getmaxy 2 setcolor getmaxcolor draw the circle circle midx midy radius clean up getch closegraph return 0 函数名 cleardevice 功 能 清除图形屏幕 用 法 void far cleardevice void 程序例 include include include include int main void request auto detection int gdriver DETECT gmode errorcode int midx midy initialize graphics and local variables initgraph 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 for centering screen messages settextjustify CENTER TEXT CENTER TEXT output a message to the screen C 语言常用函数 第 21 页 共 250 页 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 函数名 clearerr 功 能 复位错误标志 用 法 void clearerr FILE stream 程序例 include 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 C 语言常用函数 第 22 页 共 250 页 函数名 clearviewport 功 能 清除图形视区 用 法 void far clearviewport void 程序例 include include include include 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 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 C 语言常用函数 第 23 页 共 250 页 output another message outtextxy 0 0 Press any key to quit clean up getch closegraph return 0 函数名 close close 功 能 关闭文件句柄 用 法 int close int handle 程序例 include include include include 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 函数名 clock 功 能 确定处理器时间 用 法 clock t clock void 程序例 include include include int main void C 语言常用函数 第 24 页 共 250 页 clock t start end start clock delay 2000 end clock printf The time was f n end start CLK TCK return 0 函数名 closegraph 功 能 关闭图形系统 用 法 void far closegraph void 程序例 include include include include int main void request auto detection int gdriver DETECT gmode errorcode int x y initialize graphics mode initgraph 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 C 语言常用函数 第 25 页 共 250 页 printf Press any key to halt getch return 0 函数名 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 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 函数名 clrscr 功 能 清除文本模式窗口 用 法 void clrscr void 程序例 include 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 C 语言常用函数 第 26 页 共 250 页 函数名 coreleft 功 能 返回未使用内存的大小 用 法 unsigned coreleft void 程序例 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 return 0 函数名 cos 功 能 余弦函数 用 法 double cos double x 程序例 include include int main void double result double x 0 5 result cos x printf The cosine of lf is lf n x result return 0 函数名 cosh 功 能 双曲余弦函数 用 法 dluble cosh double x 程序例 include include 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 C 语言常用函数 第 27 页 共 250 页 程序例 include include define USA 0 int main void struct COUNTRY country info country USA printf The currency symbol for the USA is s n country info co curr return 0 函数名 cprintf 功 能 送格式化输出至屏幕 用 法 int cprintf const char format argument 程序例 include 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 函数名 cputs 功 能 写字符到屏幕 用 法 void cputs const char string 程序例 include 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 C 语言常用函数 第 28 页 共 250 页 wait for a key getch return 0 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 程序例 include include include include 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 函数名 creatnew 功 能 创建一个新文件 用 法 int creatnew const char filename int attrib 程序例 include include include include include int main void int handle char buf 11 0123456789 attempt to create a file that doesn t already exist handle creatnew DUMMY FIL 0 C 语言常用函数 第 29 页 共 250 页 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 程序例 include include include 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 函数名 cscanf 功 能 从控制台执行格式化输入 用 法 int cscanf char format argument 程序例 include int main void char string 80 clear the screen clrscr Prompt the user for input cprintf Enter a string w