最全古典小說網 由本軟件公布所得
main()主函數 每一C 程序都必須有一main()函數, 能夠依據自己的愛好把它放在程序的某
個地方。有些程序猿把它放在最前面, 而還有一些程序猿把它放在最后面, 不管放
在哪個地方, 下面幾點說明都是適合的。
1. main() 參數 在Turbo C2.0啟動過程中, 傳遞main()函數三個參數: argc, argv和env。
* argc: 整數, 為傳給main()的命令行參數個數。
* argv: 字符串數組。 在DOS 3.X 版本號中, argv[0] 為程序運行的全路徑名; 對DOS 3.0 下面的版本號, argv[0]為空串("") 。
argv[1] 為在DOS命令行中運行程序名后的第一個字符串; argv[2] 為運行程序名后的第二個字符串; ... argv[argc]為NULL。 *env: 安符串數組。
env[] 的每個元素都包括ENVVAR=value形式的字符
串。
當中ENVVAR為環境變量如PATH或87。value 為ENVVAR的相應值如C:\DOS, C:
\TURBOC(對于PATH) 或YES(對于87)。
Turbo C2.0啟動時總是把這三個參數傳遞給main()函數, 能夠在用戶程序中
說明(或不說明)它們, 假設說明了部分(或所有)參數, 它們就成為main()子程序
的局部變量。
請注意: 一旦想說明這些參數, 則必須按argc, argv, env 的順序, 例如以下面
的樣例:
main() main(int argc) main(int argc, char *argv[]) main(int argc, char *argv[], char *env[])
當中另外一種情況是合法的, 但不常見, 由于在程序中非常少有僅僅用argc, 而不
用argv[]的情況。
下面提供一例子程序EXAMPLE.EXE, 演示怎樣在main()函數中使用三個參數: /*program name EXAMPLE.EXE*/ #include <stdio.h> #include <stdlib.h> main(int argc, char *argv[], char *env[]) { int i; printf("These are the %d command- line arguments passed to main:\n\n", argc); for(i=0; i<=argc; i++) printf("argv[%d]:%s\n", i, argv[i]); printf("\nThe environment string(s)on this system are:\n\n"); for(i=0; env[i]!=NULL; i++) printf(" env[%d]:%s\n", i, env[i]); } 假設在DOS 提示符下, 按下面方式執行EXAMPLE.EXE: C:\example first_argument "argument with blanks" 3 4 "last but one" stop! 注意: 能夠用雙引號括起內含空格的參數, 如本例中的: " argument with blanks"和"Last but one")。
結果是這種: The value of argc is 7 These are the 7 command-linearguments passed to main: argv[0]:C:\TURBO\EXAMPLE.EXE argv[1]:first_argument argv[2]:argument with blanks argv[3]:3 argv[4]:4 argv[5]:last but one argv[6]:stop! argv[7]:(NULL) The environment string(s) on this system are: env[0]: COMSPEC=C:\COMMAND.COM env[1]: PROMPT=$P$G /*視詳細設置而定*/ env[2]: PATH=C:\DOS;C:\TC /*視詳細設置而定*/
應該提醒的是: 傳送main() 函數的命令行參數的最大長度為128 個字符 (包
括參數間的空格), 這是由DOS 限制的。
函數名: matherr
功 能: 用戶可改動的數學錯誤處理程序
用 法: int matherr(struct exception *e);
程序例:
/* This is a user-defined matherr function that prevents any error messages from being printed. */ #include<math.h> int matherr(struct exception *a) { return 1; }
函數名: memccpy
功 能: 從源source中拷貝n個字節到目標destin中
用 法: void *memccpy(void *destin, void *source, unsigned char ch,
unsigned n);
程序例:
#include <string.h> #include <stdio.h> int main(void) { char *src = "This is the source string"; char dest[50]; char *ptr; ptr = memccpy(dest, src, 'c', strlen(src)); if (ptr) { *ptr = '\0'; printf("The character was found: %s\n", dest); } else printf("The character wasn't found\n"); return 0; }
函數名: malloc
功 能: 內存分配函數
用 法: void *malloc(unsigned size);
程序例:
#include <stdio.h> #include <string.h> #include <alloc.h> #include <process.h> int main(void) { char *str; /* allocate memory for string */ /* This will generate an error when compiling */ /* with C++, use the new operator instead. */ if ((str = malloc(10)) == NULL) { printf("Not enough memory to allocate buffer\n"); exit(1); /* terminate program if out of memory */ } /* copy "Hello" into string */ strcpy(str, "Hello"); /* display string */ printf("String is %s\n", str); /* free memory */ free(str); return 0; }
函數名: memchr
功 能: 在數組的前n個字節中搜索字符
用 法: void *memchr(void *s, char ch, unsigned n);
程序例:
#include <string.h> #include <stdio.h> int main(void) { char str[17]; char *ptr; strcpy(str, "This is a string"); ptr = memchr(str, 'r', strlen(str)); if (ptr) printf("The character 'r' is at position: %d\n", ptr - str); else printf("The character was not found\n"); return 0; }
函數名: memcpy
功 能: 從源source中拷貝n個字節到目標destin中
用 法: void *memcpy(void *destin, void *source, unsigned n);
程序例:
#include <stdio.h> #include <string.h> int main(void) { char src[] = "******************************"; char dest[] = "abcdefghijlkmnopqrstuvwxyz0123456709"; char *ptr; printf("destination before memcpy: %s\n", dest); ptr = memcpy(dest, src, strlen(src)); if (ptr) printf("destination after memcpy: %s\n", dest); else printf("memcpy failed\n"); return 0; }
函數名: memicmp
功 能: 比較兩個串s1和s2的前n個字節, 忽略大寫和小寫
用 法: int memicmp(void *s1, void *s2, unsigned n);
程序例:
#include <stdio.h> #include <string.h> int main(void) { char *buf1 = "ABCDE123"; char *buf2 = "abcde456"; int stat; stat = memicmp(buf1, buf2, 5); printf("The strings to position 5 are "); if (stat) printf("not "); printf("the same\n"); return 0; }
函數名: memmove
功 能: 移動一塊字節
用 法: void *memmove(void *destin, void *source, unsigned n);
程序例:
#include <string.h> #include <stdio.h> int main(void) { char *dest = "abcdefghijklmnopqrstuvwxyz0123456789"; char *src = "******************************"; printf("destination prior to memmove: %s\n", dest); memmove(dest, src, 26); printf("destination after memmove: %s\n", dest); return 0; }
函數名: memset
功 能: 設置s中的全部字節為ch, s數組的大小由n給定
用 法: void *memset(void *s, char ch, unsigned n);
程序例:
#include <string.h> #include <stdio.h> #include <mem.h> int main(void) { char buffer[] = "Hello world\n"; printf("Buffer before memset: %s\n", buffer); memset(buffer, '*', strlen(buffer) - 1); printf("Buffer after memset: %s\n", buffer); return 0; }
函數名: mkdir
功 能: 建立一個文件夾
用 法: int mkdir(char *pathname);
程序例:
#include <stdio.h> #include <conio.h> #include <process.h> #include <dir.h> int main(void) { int status; clrscr(); status = mkdir("asdfjklm"); (!status) ? (printf("Directory created\n")) : (printf("Unable to create directory\n")); getch(); system("dir"); getch(); status = rmdir("asdfjklm"); (!status) ? (printf("Directory deleted\n")) : (perror("Unable to delete directory")); return 0; }
函數名: mktemp
功 能: 建立唯一的文件名稱
用 法: char *mktemp(char *template);
程序例:
#include <dir.h> #include <stdio.h> int main(void) { /* fname defines the template for the temporary file. */ char *fname = "TXXXXXX", *ptr; ptr = mktemp(fname); printf("%s\n",ptr); return 0; }
函數名: MK_FP
功 能: 設置一個遠指針
用 法: void far *MK_FP(unsigned seg, unsigned off);
程序例:
#include <dos.h> #include <graphics.h> int main(void) { int gd, gm, i; unsigned int far *screen; detectgraph(&gd, &gm); if (gd == HERCMONO) screen = MK_FP(0xB000, 0); else screen = MK_FP(0xB800, 0); for (i=0; i<26; i++) screen[i] = 0x0700 + ('a' + i); return 0; }
函數名: modf
功 能: 把數分為指數和尾數
用 法: double modf(double value, double *iptr);
程序例:
#include <math.h> #include <stdio.h> int main(void) { double fraction, integer; double number = 100000.567; fraction = modf(number, &integer); printf("The whole and fractional parts of %lf are %lf and %lf\n", number, integer, fraction); return 0; }
函數名: movedata
功 能: 拷貝字節
用 法: void movedata(int segsrc, int offsrc, int segdest,
int offdest, unsigned numbytes);
程序例:
#include <mem.h> #define MONO_BASE 0xB000 /* saves the contents of the monochrome screen in buffer */ void save_mono_screen(char near *buffer) { movedata(MONO_BASE, 0, _DS, (unsigned)buffer, 80*25*2); } int main(void) { char buf[80*25*2]; save_mono_screen(buf); }
函數名: moverel
功 能: 將當前位置(CP)移動一相對距離
用 法: void far moverel(int dx, int dy);
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; char msg[80]; /* 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 */ } /* move the C.P. to location (20, 30) */ moveto(20, 30); /* plot a pixel at the C.P. */ putpixel(getx(), gety(), getmaxcolor()); /* create and output a message at (20, 30) */ sprintf(msg, " (%d, %d)", getx(), gety()); outtextxy(20, 30, msg); /* move to a point a relative distance */ /* away from the current value of C.P. */ moverel(100, 100); /* plot a pixel at the C.P. */ putpixel(getx(), gety(), getmaxcolor()); /* create and output a message at C.P. */ sprintf(msg, " (%d, %d)", getx(), gety()); outtext(msg); /* clean up */ getch(); closegraph(); return 0; }
函數名: movetext
功 能: 將屏幕文本從一個矩形區域復制到還有一個矩形區域
用 法: int movetext(int left, int top, int right, int bottom,
int newleft, int newtop);
程序例:
#include <conio.h> #include <string.h> int main(void) { char *str = "This is a test string"; clrscr(); cputs(str); getch(); movetext(1, 1, strlen(str), 2, 10, 10); getch(); return 0; }
函數名: moveto
功 能: 將CP移到(x, y)
用 法: void far moveto(int x, int y);
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; char msg[80]; /* 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 */ } /* move the C.P. to location (20, 30) */ moveto(20, 30); /* plot a pixel at the C.P. */ putpixel(getx(), gety(), getmaxcolor()); /* create and output a message at (20, 30) */ sprintf(msg, " (%d, %d)", getx(), gety()); outtextxy(20, 30, msg); /* move to (100, 100) */ moveto(100, 100); /* plot a pixel at the C.P. */ putpixel(getx(), gety(), getmaxcolor()); /* create and output a message at C.P. */ sprintf(msg, " (%d, %d)", getx(), gety()); outtext(msg); /* clean up */ getch(); closegraph(); return 0; }
函數名: movemem
功 能: 移動一塊字節
用 法: void movemem(void *source, void *destin, unsigned len);
程序例:
#include <mem.h> #include <alloc.h> #include <stdio.h> #include <string.h> int main(void) { char *source = "Borland International"; char *destination; int length; length = strlen(source); destination = malloc(length + 1); movmem(source,destination,length); printf("%s\n",destination); return 0; }
函數名: normvideo
功 能: 選擇正常亮度字符
用 法: void normvideo(void);
程序例:
#include <conio.h> int main(void) { normvideo(); cprintf("NORMAL Intensity Text\r\n"); return 0; }
函數名: nosound
功 能: 關閉PC揚聲器
用 法: void nosound(void);
程序例:
/* Emits a 7-Hz tone for 10 seconds. True story: 7 Hz is the resonant frequency of a chicken's skull cavity. This was determined empirically in Australia, where a new factory generating 7-Hz tones was located too close to a chicken ranch: When the factory started up, all the chickens died. Your PC may not be able to emit a 7-Hz tone. */ int main(void) { sound(7); delay(10000); nosound(); }
書畫小說軟件 制作更滿意的讀、更舒心的寫、更輕松的公布
最全古典小說網 由本軟件公布所得
