main()主函数?
????每一C?程序都必须有一main()函数,?可以根据自己的爱好把它放在程序的某?
个地方。有些程序员把它放在最前面,?而另一些程序员把它放在最后面,?无论放?
在哪个地方,?以下几点说明都是适合的。?
1.?main()?参数?
????在Turbo?C2.0启动过程中,?传递main()函数三个参数:?argc,?argv和env。?
?????*?argc:??整数,?为传给main()的命令行参数个数。?
?????*?argv:??字符串数组。?
??????????????在DOS?3.X?版本中,?argv[0]?为程序运行的全路径名;?对DOS?3.0?
??????????????以下的版本,?argv[0]为空串("")?。?
??????????????argv[1]?为在DOS命令行中执行程序名后的第一个字符串;?
??????????????argv[2]?为执行程序名后的第二个字符串;?
??????????????...?
??????????????argv[argc]为NULL。?
?????*env:??安符串数组。env[]?的每一个元素都包含ENVVAR=value形式的字符?
串。其中ENVVAR为环境变量如PATH或87。value?为ENVVAR的对应值如C:\DOS,?C:?
(对于PATH)?或YES(对于87)。?
????Turbo?C2.0启动时总是把这三个参数传递给main()函数,?可以在用户程序中?
说明(或不说明)它们,?如果说明了部分(或全部)参数,?它们就成为main()子程序?
的局部变量。?
argc,?argv,?env?的顺序,?如以下?
的例子:?
main()?
?????main(int?argc)?
?????main(int?argc,?char?*argv[])?
?????main(int?argc,?char?*argv[],?char?*env[])?
????
其中第二种情况是合法的,?但不常见,?因为在程序中很少有只用argc,?而不?
用argv[]的情况。?
main()函数中使用三个参数:?
?????/*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]);?
?????}?
????如果在DOS?提示符下,?按以下方式运行EXAMPLE.EXE:?
????C:\example?first_argument?"argument?with?blanks"??3??4??"last??but?
one"?stop!?
????注意:?可以用双引号括起内含空格的参数,?如本例中的:???"??argument?
with?blanks"和"Last?but?one")。?
????结果是这样的:?
?????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????????????/*视具体设置而定*/?
?????env[2]:?PATH=C:\DOS;C:\TC??????/*视具体设置而定*/?
??
?????应该提醒的是:?传送main()?函数的命令行参数的最大长度为128?个字符?(包?
括参数间的空格),??这是由DOS?限制的。?
函数名:?matherr?
功??能:?用户可修改的数学错误处理程序?
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;?
}?
??
??
??
函数名:?memccpy?
功??能:?从源source中拷贝n个字节到目标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;?
}?
??
??
函数名:?malloc?
功??能:?内存分配函数?
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;?
}?
??
??
??
函数名:?memchr?
功??能:?在数组的前n个字节中搜索字符?
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;?
}?
??
函数名:?memcpy?
功??能:?从源source中拷贝n个字节到目标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;?
}?
??
??
函数名:?memicmp?
功??能:?比较两个串s1和s2的前n个字节,?忽略大小写?
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;?
}?
??
??
函数名:?memmove?
功??能:?移动一块字节?
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;?
}?
??
??
??
函数名:?memset?
功??能:?设置s中的所有字节为ch,?s数组的大小由n给定?
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;?
}?
??
??
函数名:?mkdir?
功??能:?建立一个目录?
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;?
}?
??
??
??
函数名:?mktemp?
功??能:?建立唯一的文件名?
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;?
}?
??
??
函数名:?MK_FP?
功??能:?设置一个远指针?
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;?
}?
??
??
函数名:?modf?
功??能:?把数分为指数和尾数?
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;?
}?
??
??
函数名:?movedata?
功??能:?拷贝字节?
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);?
}?
??
??
函数名:?moverel?
功??能:?将当前位置(CP)移动一相对距离?
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;?
}?
??
??
函数名:?movetext?
功??能:?将屏幕文本从一个矩形区域拷贝到另一个矩形区域?
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;?
}?
??
??
函数名:?moveto?
功??能:?将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;?
}?
??
??
函数名:?movemem?
功??能:?移动一块字节?
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;?
}?
??
??
函数名:?normvideo?
功??能:?选择正常亮度字符?
用??法:?void?normvideo(void);?
程序例:?
#include?<conio.h>?
int?main(void)?
{?
???normvideo();?
???cprintf("NORMAL?Intensity?Text\r\n");?
???return?0;?
}?
??
??
函数名:?nosound?
功??能:?关闭PC扬声器?
用??法:?void?nosound(void);?
程序例:?
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();?
}?
??
??
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