C语言功能 --C-白红宇

C语言功能 --C

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发布时间：2019-06-18

本文共 15186 字，大约阅读时间需要 50 分钟。

功能名称: cabs

动力能够: 计算绝对复数值

使用法国: double cabs(struct complex z);

程序示例:

#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);    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, &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: 改变工作文件夹

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);    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: 改变文件的訪问方式

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); }

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(&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 
      
        #include 
       
         #include 
        
          #include 
         
           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 
      
        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 
      
        #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 */    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 
      
        #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) {
         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(&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: 在文本窗体中清除字符到行末

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: 清除文本模式窗体

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; }

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);

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: %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");    /* 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);    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: 从控制台运行格式化输入

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("\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 
      
        #include 
       
         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 
      
        #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 
        
          to quit:\n");    }    return 0; }