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      學(xué)習(xí)啦 > 學(xué)習(xí)英語(yǔ) > 專業(yè)英語(yǔ) > 計(jì)算機(jī)英語(yǔ) > c語(yǔ)言的用法

      c語(yǔ)言的用法

      時(shí)間: 長(zhǎng)思709 分享

      c語(yǔ)言的用法

        語(yǔ)言程序設(shè)計(jì)是一門基礎(chǔ)的程序設(shè)計(jì)語(yǔ)言,學(xué)好這門課對(duì)以后程序開(kāi)發(fā)至關(guān)重要。由于C語(yǔ)言靈活、強(qiáng)大,初學(xué)者要全面地掌握它非常吃力,因此在學(xué)習(xí)C語(yǔ)言的過(guò)程中,但一定要熟練掌握C語(yǔ)言的流程控制語(yǔ)句、數(shù)組、函數(shù)、指針等基礎(chǔ)知識(shí)的應(yīng)用,為學(xué)習(xí)面向?qū)ο蟪绦蛟O(shè)計(jì)打下堅(jiān)實(shí)的基礎(chǔ)。下面小編就為大家來(lái)介紹下c語(yǔ)言的用法。
        c語(yǔ)言的用法: abort
        功 能: 異常終止一個(gè)進(jìn)程
        用 法: void abort(void);
        程序例:
        #include <stdio.h>
        #include <stdlib.h>
        int main(void)
        {
        printf("Calling abort()\n");
        abort();
        return 0; /* This is never reached */
        }
        c語(yǔ)言的用法: abs
        功 能: 求整數(shù)的絕對(duì)值
        用 法: int abs(int i);
        程序例:
        #include <stdio.h>
        #include <math.h>
        int main(void)
        {
        int number = -1234;
        printf("number: %d absolute value: %d\n", number, abs(number));
        return 0;
        }
        c語(yǔ)言的用法: absread, abswirte
        功 能: 絕對(duì)磁盤(pán)扇區(qū)讀、寫(xiě)數(shù)據(jù)
        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 <stdio.h>
        #include <conio.h>
        #include <process.h>
        #include <dos.h>
        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, &buf) != 0)
        {
        perror("Disk problem");
        exit(1);
        }
        printf("Read OK\n");
        strt = 3;
        for (i=0; i<80; i++)
        {
        ch_out = buf[strt+i];
        putchar(ch_out);
        }
        printf("\n");
        return(0);
        }
        c語(yǔ)言的用法: access
        功 能: 確定文件的訪問(wèn)權(quán)限
        用 法: int access(const char *filename, int amode);
        程序例:
        #include <stdio.h>
        #include <io.h>
        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);
        }
        c語(yǔ)言的用法: acos
        功 能: 反余弦c語(yǔ)言的用法
        用 法: double acos(double x);
        程序例:
        #include <stdio.h>
        #include <math.h>
        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語(yǔ)言的用法: allocmem
        功 能: 分配DOS存儲(chǔ)段
        用 法: int allocmem(unsigned size, unsigned *seg);
        程序例:
        #include <dos.h>
        #include <alloc.h>
        #include <stdio.h>
        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: %x\n", segp);
        else
        printf("Failed: maximum number of paragraphs available is %u\n",
        stat);
        return 0;
        }
        c語(yǔ)言的用法: arc
        功 能: 畫(huà)一弧線
        用 法: void far arc(int x, int y, int stangle, int endangle, 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 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:");
        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;
        }
        c語(yǔ)言的用法: asctime
        功 能: 轉(zhuǎn)換日期和時(shí)間為ASCII碼
        用 法: char *asctime(const struct tm *tblock);
        程序例:
        #include <stdio.h>
        #include <string.h>
        #include <time.h>
        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(&t));
        printf("%s\n", str);
        return 0;
        }
        c語(yǔ)言的用法: asin
        功 能: 反正弦c語(yǔ)言的用法
        用 法: double asin(double x);
        程序例:
        #include <stdio.h>
        #include <math.h>
        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);
        }
        c語(yǔ)言的用法: assert
        功 能: 測(cè)試一個(gè)條件并可能使程序終止
        用 法: void assert(int test);
        程序例:
        #include <assert.h>
        #include <stdio.h>
        #include <stdlib.h>
        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;
        }
        c語(yǔ)言的用法: atan
        功 能: 反正切c語(yǔ)言的用法
        用 法: double atan(double x);
        程序例:
        #include <stdio.h>
        #include <math.h>
        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語(yǔ)言的用法: atan2
        功 能: 計(jì)算Y/X的反正切值
        用 法: double atan2(double y, double x);
        程序例:
        #include <stdio.h>
        #include <math.h>
        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;
        }
        c語(yǔ)言的用法: atexit
        功 能: 注冊(cè)終止c語(yǔ)言的用法
        用 法: int atexit(atexit_t func);
        程序例:
        #include <stdio.h>
        #include <stdlib.h>
        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;
        }
        c語(yǔ)言的用法: atof
        功 能: 把字符串轉(zhuǎn)換成浮點(diǎn)數(shù)
        用 法: double atof(const char *nptr);
        程序例:
        #include <stdlib.h>
        #include <stdio.h>
        int main(void)
        {
        float f;
        char *str = "12345.67";
        f = atof(str);
        printf("string = %s float = %f\n", str, f);
        return 0;
        }
        c語(yǔ)言的用法: atoi
        功 能: 把字符串轉(zhuǎn)換成長(zhǎng)整型數(shù)
        用 法: int atoi(const char *nptr);
        程序例:
        #include <stdlib.h>
        #include <stdio.h>
        int main(void)
        {
        int n;
        char *str = "12345.67";
        n = atoi(str);
        printf("string = %s integer = %d\n", str, n);
        return 0;
        }
        c語(yǔ)言的用法: atol
        功 能: 把字符串轉(zhuǎn)換成長(zhǎng)整型數(shù)
        用 法: long atol(const char *nptr);
        程序例:
        #include <stdlib.h>
        #include <stdio.h>
        int main(void)
        {
        long l;
        char *str = "98765432";
        l = atol(lstr);
        printf("string = %s integer = %ld\n", str, l);
        return(0);
        }
        c語(yǔ)言的用法: bar
        功 能: 畫(huà)一個(gè)二維條形圖
        用 法: void far bar(int left, int top, int right, int bottom);
        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, i;
        /* 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;
        /* 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;
        }
        c語(yǔ)言的用法: bar3d
        功 能: 畫(huà)一個(gè)三維條形圖
        用 法: void far bar3d(int left, int top, int right, int bottom,
        int depth, int topflag);
        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, i;
        /* 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:");
        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;
        }
        c語(yǔ)言的用法: bdos
        功 能: DOS系統(tǒng)調(diào)用
        用 法: int bdos(int dosfun, unsigned dosdx, unsigned dosal);
        程序例:
        #include <stdio.h>
        #include <dos.h>
        /* 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);
        }
        int main(void)
        {
        printf("The current drive is %c:\n", current_drive());
        return 0;
        }
        c語(yǔ)言的用法: bdosptr
        功 能: DOS系統(tǒng)調(diào)用
        用 法: int bdosptr(int dosfun, void *argument, unsigned dosal);
        程序例:
        #include <string.h>
        #include <stdio.h>
        #include <dir.h>
        #include <dos.h>
        #include <errno.h>
        #include <stdlib.h>
        #define BUFLEN 80
        int main(void)
        {
        char buffer[BUFLEN];
        int test;
        printf("Enter full pathname of a directory\n");
        gets(buffer);
        test = bdosptr(0x3B,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;
        }
        c語(yǔ)言的用法: bioscom
        功 能: 串行I/O通信
        用 法: int bioscom(int cmd, char abyte, int port);
        程序例:
        #include <bios.h>
        #include <conio.h>
        #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;
        }
        c語(yǔ)言的用法: biosdisk
        功 能: 軟硬盤(pán)I/O
        用 法: int biosdisk(int cmd, int drive, int head, int track, int sector
        int nsects, void *buffer);
        程序例:
        #include <bios.h>
        #include <stdio.h>
        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 &= 0x02;
        (result) ? (printf("Drive A: Ready\n")) :
        (printf("Drive A: Not Ready\n"));
        return 0;
        }
        c語(yǔ)言的用法: biosequip
        功 能: 檢查設(shè)備
        用 法: int biosequip(void);
        程序例:
        #include <bios.h>
        #include <stdio.h>
        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 &= 0x02;
        (result) ? (printf("Drive A: Ready\n")) :
        (printf("Drive A: Not Ready\n"));
        return 0;
        }
        c語(yǔ)言的用法: bioskey
        功 能: 直接使用BIOS服務(wù)的鍵盤(pán)接口
        用 法: int bioskey(int cmd);
        程序例:
        #include <stdio.h>
        #include <bios.h>
        #include <ctype.h>
        #define RIGHT 0x01
        #define LEFT 0x02
        #define CTRL 0x04
        #define ALT 0x08
        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 & 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("%#02x\n", key);
        return 0;
        }
        c語(yǔ)言的用法: biosmemory
        功 能: 返回存儲(chǔ)塊大小
        用 法:int biosmemory(void);
        程序例:
        #include <stdio.h>
        #include <bios.h>
        int main(void)
        {
        int memory_size;
        memory_size = biosmemory(); /* returns value up to 640K */
        printf("RAM size = %dK\n",memory_size);
        return 0;
        }
        c語(yǔ)言的用法: biosprint
        功 能: 直接使用BIOS服務(wù)的打印機(jī)I/O
        用 法: int biosprint(int cmd, int byte, int port);
        程序例:
        #include <stdio.h>
        #include <conio.h>
        #include <bios.h>
        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 & 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;
        }
        c語(yǔ)言的用法: biostime
        功 能: 讀取或設(shè)置BIOS時(shí)間
        用 法: long biostime(int cmd, long newtime);
        程序例:
        #include <stdio.h>
        #include <bios.h>
        #include <time.h>
        #include <conio.h>
        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;
        }
        c語(yǔ)言的用法: brk
        功 能: 改變數(shù)據(jù)段空間分配
        用 法: int brk(void *endds);
        程序例:
        #include <stdio.h>
        #include <alloc.h>
        int main(void)
        {
        char *ptr;
        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;
        }
        c語(yǔ)言的用法: 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 <stdlib.h>
        #include <stdio.h>
        #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;
        }
        c語(yǔ)言的用法: cabs
        功 能: 計(jì)算復(fù)數(shù)的絕對(duì)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;
        }
        c語(yǔ)言的用法: calloc
        功 能: 分配主存儲(chǔ)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;
        }
        c語(yǔ)言的用法: 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;
        }
        c語(yǔ)言的用法: cgets
        功 能: 從控制臺(tái)讀字符串
        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;
        }
        c語(yǔ)言的用法: chdir
        功 能: 改變工作目錄
        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;
        }
        c語(yǔ)言的用法: _chmod, chmod
        功 能: 改變文件的訪問(wèn)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);
        }
        c語(yǔ)言的用法: chsize
        功 能: 改變文件大小
        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;
        }
        c語(yǔ)言的用法: circle
        功 能: 在給定半徑以(x, y)為圓心畫(huà)圓
        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;
        }
        c語(yǔ)言的用法: cleardevice
        功 能: 清除圖形屏幕
        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;
        }
        c語(yǔ)言的用法: clearerr
        功 能: 復(fù)位錯(cuò)誤標(biāo)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;
        }
        c語(yǔ)言的用法: clearviewport
        功 能: 清除圖形視區(qū)
        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;
        }
        c語(yǔ)言的用法: _close, close
        功 能: 關(guān)閉文件句柄
        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;
        }
        c語(yǔ)言的用法: clock
        功 能: 確定處理器時(shí)間
        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;
        }
        c語(yǔ)言的用法: closegraph
        功 能: 關(guān)閉圖形系統(tǒng)
        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;
        }
        c語(yǔ)言的用法: 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;
        }
        c語(yǔ)言的用法: 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;
        }
        c語(yǔ)言的用法: coreleft
        功 能: 返回未使用內(nèi)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;
        }
        c語(yǔ)言的用法: cos
        功 能: 余弦c語(yǔ)言的用法
        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;
        }
        c語(yǔ)言的用法: cosh
        功 能: 雙曲余弦c語(yǔ)言的用法
        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;
        }
        c語(yǔ)言的用法: country
        功 能: 返回與國(guó)家有關(guān)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;
        }
        c語(yǔ)言的用法: cprintf
        功 能: 送格式化輸出至屏幕
        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;
        }
        c語(yǔ)言的用法: cputs
        功 能: 寫(xiě)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;
        }
        c語(yǔ)言的用法: _creat creat
        功 能: 創(chuàng)建一個(gè)新文件或重寫(xiě)一個(gè)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;
        }
        c語(yǔ)言的用法: creatnew
        功 能: 創(chuàng)建一個(gè)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;
        }
        c語(yǔ)言的用法: creattemp
        功 能: 創(chuàng)建一個(gè)新文件或重寫(xiě)一個(gè)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;
        }
        c語(yǔ)言的用法: cscanf
        功 能: 從控制臺(tái)執(zhí)行格式化輸入
        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;
        }
        c語(yǔ)言的用法: ctime
        功 能: 把日期和時(shí)間轉(zhuǎn)換為字符串
        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;
        }
        c語(yǔ)言的用法: ctrlbrk
        功 能: 設(shè)置Ctrl-Break處理程序
        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;
        }
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