利用文件代号随机读取磁盘文件

1、;利用文件代号随机读取磁盘文件;.model small;.386.stack64;*;.datahandledw?recindxdw?errcdedb0promptdb'record number?'ioareadb32 dup(' ')pathnamdb'd:name.dat',0openmsgdb'* open error *',0dh,0ahreadmsgdb'* read error *',0dh,0ahrowdb0coldb0;recdparlabelbytemaxlendb3actlendb?recd

2、nodb3 dup(' ');*;.codemainprocfarmovax,datamovds,axmoves,ax;movax,0600hcallscrn;清屏callcurs;定位光标call openran;打开文件cmperrcde,0jnzexit;打开文件错callsub:callrecnum;获得键入记录号cmpactlen,0;键入记录号长度为0,结束jeexitcall readran;读磁盘文件记录cmperrcde,0jnznextcalldisp;读成功，显示该记录next:jmpcallsub;循环exit:movax,4c00hint21hmain

3、endp;-; 功能：打开ASCIZ串指定文件。;openranprocmovah,3dhmoval,0leadx,pathnamint 21hjcerrm1movhandle,axreterrm1:moverrcde,1leadx,openmsgcallerrorp;打开错，显示提示字符串retopenranendp;-;功能：键入欲读记录号;recnumprocmovah,40hmovbx,1movcx,14leadx,prompt;人机交互int 21h;movah,0ahleadx,recdpar;键入记录号字符串int21h;cmpactlen,1jbendd;键入串长0为结束标志j

4、atwodgtxorah,ahmoval,recdnojmpconvtwodgt:movah,recdnomoval,recdno+1conv:andax,0f0fhaad;两位十进制数转为二进制数decax;减1,转为0开始记录号movcl,05;教材左移4位，是乘16,错shlax,cl;记录号*32转为地址movrecindx,axendd:movcol,20callcurs;定位光标retrecnumendp;-;功能：读文件记录;readranprocmovah,42h;移动文件指针moval,0movbx,handlemovcx,0movdx,recindx;cx:dx定位文件中地

5、址int21hjcerrm2;movah,3fh;以文件代号读文件movbx,handlemovcx,32leadx,ioarea;读入缓冲区int 21hjcerrm2cmpioarea,1ahjeexit2jmpbackerrm2:leadx,readmsg;读文件错callerrorpexit2:moverrcde,1back:retreadranendp;-;功能：显示一个记录;dispprocmovah,40hmovbx,1movcx,32leadx,ioareaint 21hmovcol,0cmprow,20jaescrolincrowjmpreturnscrol:movax,0601hcallscrncallcursreturn:retdispendp;-;设置屏幕。;scrn proc mov bh,1eh mov cx,0 mov dx,184fh int 10h retscrn endp;-;设置光标位置。;curs proc mov ah,2 mov bh,0 mov dh,row mov dl,col int 10h retcurs end