后一页前一页 C 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 <stdio.h> #include <math.h> 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 <stdio.h> #include <alloc.h> 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 <math.h> #include <stdio.h> int main(void) {    double number = 123.54;    double down, up;    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);    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 <stdio.h> #include <conio.h> 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, &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);    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 <stdio.h> #include <stdlib.h> #include <dir.h> 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);    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 <sys\stat.h> #include <stdio.h> #include <io.h> 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); }       函数名: chsize 功  能: 改变文件大小 用  法: int chsize(int handle, long size); 程序例: #include <string.h> #include <fcntl.h> #include <io.h> 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 <graphics.h> #include <stdlib.h> #include <stdio.h> #include <conio.h> 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: %s\n", grapherrormsg(errorcode));       printf("Press any key to halt:");       getch();       exit(1); /* terminate with an error code */    }    midx = getmaxx() / 2;    midy = getmaxy() / 2;    setcolor(getmaxcolor());    /* draw 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 <graphics.h> #include <stdlib.h> #include <stdio.h> #include <conio.h> 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: %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 */    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 <stdio.h> int main(void) {    FILE *fp;    char ch;    /* open a file for writing */    fp = fopen("DUMMY.FIL", "w");    /* force an error condition by attempting to read */    ch = fgetc(fp);    printf("%c\n",ch);    if (ferror(fp))    {       /* display an error message */       printf("Error reading from DUMMY.FIL\n");       /* reset the error and EOF indicators */       clearerr(fp);    }    fclose(fp);    return 0; }       函数名: clearviewport 功  能: 清除图形视区 用  法: void far clearviewport(void); 程序例: #include <graphics.h> #include <stdlib.h> #include <stdio.h> #include <conio.h> #define CLIP_ON 1   /* activates clipping in viewport */ int main(void) {    /* request auto detection */    int gdriver = DETECT, gmode, errorcode;    int ht;    /* initialize graphics and local variables */    initgraph(&gdriver, &gmode, "");    /* read result of initialization */    errorcode = graphresult();    if (errorcode != grOk)  /* an error occurred */    {       printf("Graphics error: %s\n", grapherrormsg(errorcode));       printf("Press any key to halt:");       getch();       exit(1); /* terminate with an error code */    }    setcolor(getmaxcolor());    ht = textheight("W");    /* message in default full-screen viewport */    outtextxy(0, 0, "* <-- (0, 0) in default viewport");    /* create a smaller viewport */    setviewport(50, 50, getmaxx()-50, getmaxy()-50, CLIP_ON);    /* display some messages */    outtextxy(0, 0, "* <-- (0, 0) in smaller viewport");    outtextxy(0, 2*ht, "Press any key to clear viewport:");    /* wait for a key */    getch();    /* clear the viewport */    clearviewport();    /* output another message */    outtextxy(0, 0, "Press any key to quit:");    /* clean up */    getch();    closegraph();    return 0; }       函数名: _close, close 功  能: 关闭文件句柄 用  法: int close(int handle); 程序例: #include <string.h> #include <stdio.h> #include <fcntl.h> #include <io.h> main() {    int handle;    char buf[11] = "0123456789";    /* create a file containing 10 bytes */    handle = open("NEW.FIL", O_CREAT);    if (handle > -1)    {        write(handle, buf, strlen(buf));        /* close the file */        close(handle);    }    else    {        printf("Error opening file\n");    }    return 0; }       函数名: clock 功  能: 确定处理器时间 用  法: clock_t clock(void); 程序例: #include <time.h> #include <stdio.h> #include <dos.h> int main(void) {    clock_t start, end;    start = clock();    delay(2000);    end = clock();    printf("The time was: %f\n", (end - start) / CLK_TCK);    return 0; }       函数名: closegraph 功  能: 关闭图形系统 用  法: void far closegraph(void); 程序例: #include <graphics.h> #include <stdlib.h> #include <stdio.h> #include <conio.h> int main(void) {    /* request auto detection */    int gdriver = DETECT, gmode, errorcode;    int x, y;    /* initialize graphics mode */    initgraph(&gdriver, &gmode, "");    /* read result of initialization */    errorcode = graphresult();    if (errorcode != grOk)  /* an error       occurred */    {       printf("Graphics error: %s\n", grapherrormsg(errorcode));       printf("Press any key to halt:");       getch();       exit(1); /* terminate with an error code */    }    x = getmaxx() / 2;    y = getmaxy() / 2;    /* output a message */    settextjustify(CENTER_TEXT, CENTER_TEXT);    outtextxy(x, y, "Press a key to close the graphics system:");    /* wait for a key */    getch();    /* closes down the graphics system */    closegraph();    printf("We're now back in text mode.\n");    printf("Press any key to halt:");    getch();    return 0; }       函数名: 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 <conio.h> int main(void) {    clrscr();    cprintf("The function CLREOL clears all characters from the\r\n");    cprintf("cursor position to the end of the line within the\r\n");    cprintf("current text window, without moving the cursor.\r\n");    cprintf("Press any key to continue . . .");    gotoxy(14, 4);    getch();    clreol();    getch();    return 0; }       函数名: clrscr 功  能: 清除文本模式窗口 用  法: void clrscr(void); 程序例: #include <conio.h> int main(void) {    int i;    clrscr();    for (i = 0; i < 20; i++)       cprintf("%d\r\n", i);    cprintf("\r\nPress any key to clear screen");    getch();    clrscr();    cprintf("The screen has been cleared!");    getch();    return 0; }       函数名: coreleft 功  能: 返回未使用内存的大小 用  法: unsigned coreleft(void); 程序例: #include <stdio.h> #include <alloc.h> int main(void) {    printf("The difference between the highest allocated block and\n");    printf("the top of the heap is: %lu bytes\n", (unsigned long) coreleft());    return 0; }   函数名: cos 功  能: 余弦函数 用  法: double cos(double x); 程序例: #include <stdio.h> #include <math.h> int main(void) {    double result;    double x = 0.5;    result = cos(x);    printf("The cosine of %lf is %lf\n", x, result);    return 0; }       函数名: cosh 功  能: 双曲余弦函数 用  法: dluble cosh(double x); 程序例: #include <stdio.h> #include <math.h> int main(void) {    double result;    double x = 0.5;    result = cosh(x);    printf("The hyperboic cosine of %lf is %lf\n", x, result);    return 0; }       函数名: 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 <dos.h> #include <stdio.h> #define USA 0 int main(void) {    struct COUNTRY country_info;    country(USA, &country_info);    printf("The currency symbol for the USA is: %s\n",            country_info.co_curr);    return 0; }       函数名: cprintf 功  能: 送格式化输出至屏幕 用  法: int cprintf(const char *format[, argument, ...]); 程序例: #include <conio.h> int main(void) {    /* clear the screen */    clrscr();    /* create a text window */    window(10, 10, 80, 25);    /* output some text in the window */    cprintf("Hello world\r\n");    /* wait for a key */    getch();    return 0; }       函数名: cputs 功  能: 写字符到屏幕 用  法: void cputs(const char *string); 程序例: #include <conio.h> int main(void) {    /* clear the screen */    clrscr();    /* create a text window */    window(10, 10, 80, 25);    /* output some text in the window */    cputs("This is within the window\r\n");    /* wait for a key */    getch();    return 0; }       函数名: _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 <sys\stat.h> #include <string.h> #include <fcntl.h> #include <io.h> int main(void) {    int handle;    char buf[11] = "0123456789";    /* change the default file mode from text to binary */    _fmode = O_BINARY;    /* create a binary file for reading and writing */    handle = creat("DUMMY.FIL", S_IREAD | S_IWRITE);    /* write 10 bytes to the file */    write(handle, buf, strlen(buf));    /* close the file */    close(handle);    return 0; }   函数名: creatnew 功  能: 创建一个新文件 用  法: int creatnew(const char *filename, int attrib); 程序例: #include <string.h> #include <stdio.h> #include <errno.h> #include <dos.h> #include <io.h> int main(void) {    int handle;    char buf[11] = "0123456789";    /* attempt to create a file that doesn't already exist */    handle = creatnew("DUMMY.FIL", 0);    if (handle == -1)       printf("DUMMY.FIL already exists.\n");    else    {       printf("DUMMY.FIL successfully created.\n");       write(handle, buf, strlen(buf));       close(handle);    }    return 0; }       函数名: 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 <string.h> #include <stdio.h> #include <io.h> int main(void) {    int handle;    char pathname[128];    strcpy(pathname, "\\");    /* create a unique file in the root directory */    handle = creattemp(pathname, 0);    printf("%s was the unique file created.\n", pathname);    close(handle);    return 0; }       函数名: 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 <conio.h> int main(void) {    char string[80];    /* clear the screen */    clrscr();    /* Prompt the user for input */    cprintf("Enter a string with no spaces:");    /* read the input */    cscanf("%s", string);    /* display what was read */    cprintf("\r\nThe string entered is: %s", string);    return 0; }       函数名: 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 <stdio.h> #include <time.h> int main(void) {    time_t t;    time(&t);    printf("Today's date and time: %s\n", ctime(&t));    return 0; }       函数名: ctrlbrk 功  能: 设置Ctrl-Break处理程序 用  法: void ctrlbrk(*fptr)(void); 程序例: #include <stdio.h> #include <dos.h> #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 <Ctrl-Break> to quit:\n");    }    return 0; }   后一页前一页

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