文档介绍：C语言库函数(O类字母)函数名:open功能:打开一个文件用于读或写用法:intopen(char*pathname,ess[,intpermiss]);程序例:#include<>#include<>#include<>#include<>intmain(void){inthandle;charmsg[]="Helloworld";if((handle=open("TEST.$$$",O_CREAT|O_TEXT))==-1){perror("Error:");return1;}write(handle,msg,strlen(msg));close(handle);return0;}函数名:outport功能:输出整数到硬件端口中用法:voidoutport(intport,intvalue);程序例:#include<>#include<>intmain(void){intvalue=64;intport=0;outportb(port,value);printf("Value%dsenttoportnumber%d\n",value,port);return0;}函数名:outportb功能:输出字节到硬件端口中用法:voidoutportb(intport,charbyte);程序例:#include<>#include<>intmain(void){intvalue=64;intport=0;outportb(port,value);printf("Value%dsenttoportnumber%d\n",value,port);return0;}函数名:outtext功能:在视区显示一个字符串用法:voidfarouttext(charfar*textstring);程序例:#include<>#include<>#include<>#include<>intmain(void){/*requestautodetection*/intgdriver=DETECT,gmode,errorcode;intmidx,midy;/*initializegraphicsandlocalvariables*/initgraph(&gdriver,&gmode,"");/*readresultofinitialization*/errorcode=graphresult();if(errorcode!=grOk)/*urred*/{printf("Graphicserror:%s\n",grapherrormsg(errorcode));printf("Pressanykeytohalt:");getch();exit(1);/*terminatewithanerrorcode*/}midx=getmaxx()/2;midy=getmaxy()/2;/**/moveto(midx,midy);/*.*/outtext("This");outtext("is");outtext("a");outtext("test.");/*cleanup*/getch();closegraph();return0;}函数名:outtextxy功能:在指定位置显示一字符串用法:voidfarouttextxy(intx,inty,char*textstring);程序例:#include<>#include<>#include<>#include<>intmain(void){/*requestautodetection*/intgdriver=DETECT,gmode,errorcode;intmidx,midy;/*initializegraphicsandlocalvariables*/initgraph(&gdriver,&gmode,"");/*readresultofinitialization*/errorcode=graphresult();if(errorcode!=grOk)/*urred*/{printf("Graphicserror:%s\n",grapherrormsg(errorcode));printf("Pressanykeytohalt:");getch();exit(1);/*terminatewithanerrorcode*/}midx=getmaxx()/2;midy