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C语言库函数使用大全
C语言库函数使用大全 （网络版） 1-257 C语言库函数使用大全 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: %dn", 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]; 2-257 C语言库函数使用大全 printf("Insert a diskette into drive A and press any keyn"); getch(); sector = 0; if (absread(0, 1, sector, &buf) != 0) { perror("Disk problem"); exit(1); } printf("Read OKn"); 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: %sn", 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 3-257 C语言库函数使用大全 int main(void) { double result; double x = 0.5; result = acos(x); printf("The arc cosine of %lf is %lfn", x, result); return 0; } 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, &segp); if (stat == -1) printf("Allocated memory at segment: %xn", segp); else printf("Failed: maximum number of paragraphs available is %un", 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; 4-257 C语言库函数使用大全 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: %sn", 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 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 */ 5-257 C语言库函数使用大全 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(&t)); printf("%sn", 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 int main(void) { double result; double x = 0.5; result = asin(x); printf("The arc sin of %lf is %lfn", 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) { 6-257 C语言库函数使用大全 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 %lfn", 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); 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 %lfn", (y / x), result); return 0; } 7-257 C语言库函数使用大全 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 calledn"); } void exit_fn2(void) { printf("Exit function #2 calledn"); } 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; char *str = "12345.67"; f = atof(str); printf("string = %s float = %fn", 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); 8-257 C语言库函数使用大全 程序例: #include #include int main(void) { int n; char *str = "12345.67"; n = atoi(str); printf("string = %s integer = %dn", 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 = %ldn", 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 */ int gdriver = DETECT, gmode, errorcode; int midx, midy, i; /* initialize graphics and local variables */ initgraph(&gdriver, &gmode, ""); 9-257 C语言库函数使用大全 /* read result of initialization */ errorcode = graphresult(); if (errorcode != grOk) /* an error occurred */ { printf("Graphics error: %sn", 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 /* 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) { /* request auto detection */ int gdriver = DETECT, gmode, errorcode; int midx, midy, i; /* initialize graphics, local variables */ 10-257 C语言库函数使用大全 initgraph(&gdriver, &gmode, ""); /* read result of initialization */ errorcode = graphresult(); if (errorcode != grOk) /* an error occurred */ { printf("Graphics error: %sn", 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 /* 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(0x19, 0, 0); return('A' + curdrive); } 11-257 C语言库函数使用大全 int main(void) { 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 directoryn"); gets(buffer); test = bdosptr(0x3B,buffer,0); if(test) { printf("DOS error message: %dn", errno); /* See errno.h for error listings */ exit (1); } getcwd(buffer, BUFLEN); printf("The current directory is: %sn", 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); 12-257 C语言库函数使用大全 程序例: #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); } } 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 readyn"); 13-257 C语言库函数使用大全 result = biosdisk(4,0,0,0,0,1,buffer); result &= 0x02; (result) ? (printf("Drive A: Readyn")) : (printf("Drive A: Not Readyn")); 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; char buffer[512]; printf("Testing to see if drive a: is readyn"); result = biosdisk(4,0,0,0,0,1,buffer); result &= 0x02; (result) ? (printf("Drive A: Readyn")) : (printf("Drive A: Not Readyn")); 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 0x01 #define LEFT 0x02 #define CTRL 0x04 #define ALT 0x08 int main(void) { 14-257 C语言库函数使用大全 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 & 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); else printf("%#02xn", key); return 0; } 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 = %dKn",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); 15-257 C语言库函数使用大全 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 continuen"); getch(); 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"); return 0; } 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(); 16-257 C语言库函数使用大全 cprintf("The number of clock ticks since midnight is:rn"); cprintf("The number of seconds since midnight is:rn"); cprintf("The number of minutes since midnight is:rn"); cprintf("The number of hours since midnight is:rn"); cprintf("rnPress 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; printf("Changing allocation with brk()n"); ptr = malloc(1); printf("Before brk() call: %lu bytes freen", coreleft()); brk(ptr+1000); printf(" After brk() call: %lu bytes freen", coreleft()); return 0; } 函数名: bsearch 功 能: 二分法搜索 17-257 C语言库函数使用大全 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 (&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"); 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); 程序例: #include #include int main(void) { struct complex z; double val; z.x = 2.0; z.y = 1.0; val = cabs(z); 18-257 C语言库函数使用大全 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 %sn", 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); 19-257 C语言库函数使用大全 up = ceil(number); printf("original number %5.2lfn", number); printf("number rounded down %5.2lfn", down); printf("number rounded up %5.2lfn", 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 %pn", 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 %pn", p, &buffer); 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 20-257 C语言库函数使用大全 #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: \%sn", old_dir); if (chdir("\")) { perror("chdir()"); exit(1); } if (getcurdir(0, new_dir)) { perror("getcurdir()"); exit(1); } printf("Current directory is now: \%sn", new_dir); printf("nChanging back to orignal directory: \%sn", 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) 21-257 C语言库函数使用大全 { 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-onlyn", filename); else printf("Made %s read-onlyn", filename); } 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: 22-257 C语言库函数使用大全 #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(&gdriver, &gmode, ""); /* read result of initialization */ errorcode = graphresult(); if (errorcode != grOk) /* an error occurred */ { printf("Graphics error: %sn", 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 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 23-257 C语言库函数使用大全 int main(void) { /* request auto detection */ int gdriver = DETECT, gmode, errorcode; 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: %sn", 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 */ 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: 24-257 C语言库函数使用大全 #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("%cn",ch); if (ferror(fp)) { /* display an error message */ printf("Error reading from DUMMY.FILn"); /* reset the error and EOF indicators */ clearerr(fp); } fclose(fp); return 0; } 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(&gdriver, &gmode, ""); /* read result of initialization */ 25-257 C语言库函数使用大全 errorcode = graphresult(); if (errorcode != grOk) /* an error occurred */ { printf("Graphics error: %sn", 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() { 26-257 C语言库函数使用大全 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 filen"); } 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) { clock_t start, end; start = clock(); delay(2000); end = clock(); printf("The time was: %fn", (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: 27-257 C语言库函数使用大全 #include #include #include #include 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: %sn", 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: 28-257 C语言库函数使用大全 #include int main(void) { clrscr(); cprintf("The function CLREOL clears all characters from thern"); cprintf("cursor position to the end of the line within thern"); cprintf("current text window, without moving the cursor.rn"); 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("%drn", i); cprintf("rnPress any key to clear screen"); getch(); clrscr(); cprintf("The screen has been cleared!"); getch(); return 0; } 函数名: coreleft 功 能: 返回未使用内存的大小 29-257 C语言库函数使用大全 用 法: unsigned coreleft(void); 程序例: #include #include int main(void) { printf("The difference between the highest allocated block andn"); printf("the top of the heap is: %lu bytesn", (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 %lfn", 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 %lfn", x, result); 30-257 C语言库函数使用大全 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); 程序例: #include #include #define USA 0 int main(void) { struct COUNTRY country_info; country(USA, &country_info); printf("The currency symbol for the USA is: %sn", 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 worldrn"); /* wait for a key */ getch(); return 0; } 31-257 C语言库函数使用大全 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 windowrn"); /* 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)); 32-257 C语言库函数使用大全 /* 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); 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; 33-257 C语言库函数使用大全 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 with no spaces:"); /* read the input */ cscanf("%s", string); /* display what was read */ cprintf("rnThe string entered is: %s", string); return 0; } 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); 程序例: #include #include int main(void) 34-257 C语言库函数使用大全 { time_t t; time(&t); printf("Today's date and time: %sn", ctime(&t)); return 0; } 函数名: ctrlbrk 功 能: 设置Ctrl-Break处理程序 用 法: void ctrlbrk(*fptr)(void); 程序例: #include #include #define ABORT 0 int c_break(void) { printf("Control-Break pressed. Program aborting ...n"); return (ABORT); } int main(void) { ctrlbrk(c_break); for(;;) { printf("Looping... Press } return 0; } 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); 程序例: /* Emits a 440-Hz tone for 500 milliseconds */ #include int main(void) { sound(440); delay(500); nosound(); return 0; } 35-257 C语言库函数使用大全 函数名: delline 功 能: 在文本窗口中删去一行 用 法: void delline(void); 程序例: #include int main(void) { clrscr(); cprintf("The function DELLINE deletes the line containing thern"); cprintf("cursor and moves all lines below it one line up.rn"); cprintf("DELLINE operates within the currently active textrn"); cprintf("window. Press any key to continue . . ."); gotoxy(1,2); /* Move the cursor to the second line and first column */ getch(); delline(); getch(); return 0; } 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); 程序例: #include #include #include #include /* names of the various cards supported */ char *dname[] = { "requests detection", "a CGA", "an MCGA", "an EGA", "a 64K EGA", "a monochrome EGA", "an IBM 8514", "a Hercules monochrome", "an AT&T 6300 PC", "a VGA", "an IBM 3270 PC" 36-257 C语言库函数使用大全 }; int main(void) { /* returns detected hardware info. */ int gdriver, gmode, errorcode; /* detect graphics hardware available */ detectgraph(&gdriver, &gmode); /* read result of detectgraph call */ errorcode = graphresult(); if (errorcode != grOk) /* an error occurred */ { printf("Graphics error: %sn", grapherrormsg(errorcode)); printf("Press any key to halt:"); getch(); exit(1); /* terminate with an error code */ } /* display the information detected */ clrscr(); printf("You have %s video display card.n", dname[gdriver]); printf("Press any key to halt:"); getch(); return 0; } 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); 程序例: #include #include #include #include int main(void) { time_t first, second; clrscr(); first = time(NULL); /* Gets system time */ 37-257 C语言库函数使用大全 delay(2000); /* Waits 2 secs */ second = time(NULL); /* Gets system time again */ printf("The difference is: %f secondsn",difftime(second,first)); getch(); return 0; } 函数名: disable 功 能: 屏蔽中断 用 法: void disable(void); 程序例: /***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 */ count++; /* reenable interrupts at the end of the handler */ enable(); /* call the old routine */ oldhandler(); } int main(void) { /* save the old interrupt vector */ 38-257 C语言库函数使用大全 oldhandler = getvect(INTR); /* install the new interrupt handler */ setvect(INTR, handler); /* loop until the counter exceeds 20 */ while (count < 20) printf("count is %dn",count); /* reset the old interrupt handler */ setvect(INTR, oldhandler); return 0; } 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); 程序例: #include #include div_t x; int main(void) { x = div(10,3); printf("10 div 3 = %d remainder %dn", x.quot, x.rem); return 0; } 函数名: dosexterr 功 能: 获取扩展DOS错误信息 用 法: int dosexterr(struct DOSERR *dblkp); 程序例: #include #include int main(void) { FILE *fp; struct DOSERROR info; fp = fopen("perror.dat","r"); if (!fp) perror("Unable to open file for reading"); dosexterr(&info); 39-257 C语言库函数使用大全 printf("Extended DOS error information:n"); printf(" Extended error: %dn",info.exterror); printf(" Class: %xn",info.class); printf(" Action: %xn",info.action); printf(" Error Locus: %xn",info.locus); return 0; } 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); 程序例: #include #include #include #include int main(void) { time_t t; struct time d_time; struct date d_date; struct tm *local; getdate(&d_date); gettime(&d_time); t = dostounix(&d_date, &d_time); local = localtime(&t); printf("Time and Date: %sn", asctime(local)); return 0; } 函数名: drawpoly 功 能: 画多边形 用 法: void far drawpoly(int numpoints, int far *polypoints); 程序例: 40-257 C语言库函数使用大全 #include #include #include #include int main(void) { /* request auto detection */ int gdriver = DETECT, gmode, errorcode; int maxx, maxy; /* our polygon array */ int poly[10]; /* initialize graphics and local variables */ initgraph(&gdriver, &gmode, ""); /* read result of in 
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