模拟实现采用二级文件目录结构，第一级为主目录文件MFD，第二级为用户文件。目录文件UFD。
(1)    设计一个有m个用户的文件系统，每个用户最多可保存一个文件；
(2)    规定用户在一次运行中只能打开K个文件；
(3)    系统能检查键入命令的正确性，出错时应能显示出错原因；
(4)    对文件应能设置保护措施，如只能执行，允许读，允许写等；
(5) 对文件的操作设计提供一套文件操作：
CREATE          建立文件
DELETE          删除文件
OPEN            打开文件
CLOSE           关闭文件
READ            读写文件
WRITE           写文件
[color=FF00FF][size=3]下面的程序运行有错；
可我不知道怎么改；[/size][/color]
proram  fsystem(input,output);
   label   10;
   type 
y=string[10]
links=^datas;
data=record
filename:y;
pcode:links;
length:integer;
end;
link=^dataf;
dataf=recod
     ue4rname:y;
     next:links;
     end;
linkf=^dataf;
dataf=record
     filename:y;
     opening:integer;
     next:linkt;
     end;
   var
mfd:array[1..5]of linkf;
pl,ql:linkf;
ufd.p2,q2:link;
x:y;
afd,p3,q3:linkt;
t:boolean;
r,l,I,l,k,n,s,m,j:integer;
procedure print;
begin
for I:=1to n do
    begin 
    writeln(‘mfd-‘,mfd[I]^.username);
p2:=mfd[I]^next;
while p2<>nill do
    begin
    writeln(‘ufd-filename );
    writeln(p2^.filename:6,’-‘:6,p2^.pcode:6,p2^length:6);
    p2:=p2^next;
    end;
  end;
if i1<>0 then
   begin 
   p3:=afd;
   while p3<>nil do
      begin
      writeln(‘afd-filename opening’);
      writeln(p3^.filename:6,’-‘:6,p3^. opening:6);
     p3:=p3^next;
    end;
  end;
end
procedure pcreate;
begin
writeln(‘create name=’);
readln(x);
q2:=ufdd;
while(q2^.filename<>x)and(q2^.next<>nil)do
   q2:=q2^.next;
if q2^.next=nil then
   begin
   new(p2);
   q2.next:=p2;
   p2^.filename:=x;
   write(‘create code=’);
   readln(m);
   p2^.fpcode:=m;
   write(create length=’);
   readln(s);
   p2^.length:=s;
   p2^.next:=nil;
   writeln(‘create finish’);
   print;
   endelse writeln(‘file has already been created’);
   end;
   procedure popen;
   begin
   p2:=ufd;
   write(‘input filename=’);
   readln(x);
   while(p2^.filename<>x)and(p2^.next<>nil)do
   p2:=p2^.next;
if p2^.filename=x then
   begin
   if i1<>0 then
   begin
   q3:=q3^.next;
   end;
end;
    if( q3^.filename=x )then
    writeln(‘the file is on the afd’)
else
   begin
   new(p3);
   if i1=0 then afd:=p3;
   else q3^.next:=p3;
   i1:=i1+1;
   p3^.filename:=x;
   p3^.opening:=i1;
   p3^.next:=nil;
   writeln(‘the file has been opend ,file number=’.i1);
   writeln;
   writeln;
   end;
end;
else write(‘error);
writeln;
print;
end;
procedure pcreate;
begin 
write(‘the file name to be deleted=’);
readln(x);
writeln;
p3:=afd;q3:afd;
if p3^.filename<>x then
    begin
    q3:=p3;
    p3:=p3^.next;
    end;
if p3^.filename=x then
    begin
    q3^.next:=p3^.next;
    dispose(p3);
    end;
p2:=ufd;q2:ufd;
if p2^.filename<>x then
    begin
    while(p2^.filename<>x)and(p2^.next<>nil)do
        being
        q2:=p2;
        p2:=p2^.next;
        end;
if p2^.filename=xs then
    begin
    q2^.next:=p2^.next;
    dispose(p2);
    writeln(‘the file is deleted’)
    end;
else
    begin
    ufd:=p2^.next;
    dispose(p2);
    writeln(‘the file is deleted’)
    end;
print;
end;
procedure pclose;
var
j:integer;
begin
write(‘input close filename=’);
readln(x);q3:=afd;p3:=q3;j:=0;
while(q3^.filename<>x)and(q3^.next<>nil)do
being
        p3:=q3;
        q3:=p3^.next;
        end;
if(q3^.next<>nil)or(q3^.filename<>x)then
       begin
   p3^.next:=q3^.next;
   dispose(q3);
   writeln(‘end of close’);
   p3:=afd;
   while(p3^.next<>nil)do
   begin
   j:=j+1;p3:=p3^.next;
   end;
if j=0 then i1:=0;
writeln(‘afd file number=’.I);while
writeln;
end
else writeln(‘not retionnal’);
print;
end;
procedure pbye;
begin
p2:ufd;
writeln(‘ufd---filename ---pocde---length’);
while p2<>nil do
   begin
   write(p2^.filename:13);
   write(p2^.pocde:7,p2^.length:10);
   writeln;
   p2:=p2^.next;
   end;
write(‘the end of imiate    ‘);
writeln(‘1991.5’);
t:=ture;
end;
begin(*-----------------------main program---------------------------*)
write(‘user number n=’);
readln(n);
for i1:=1 to n do
   begin  
   write(‘uer mfd filename x’,I:22,’=’:=2);
   readln(x);
   new (mfd[I]);
   p1:=mfd[I];
   p1:=mfd[I];
   p1^.username:=x;
   p1^.next:=nil;
   write(‘input(‘,I:2,’)’);
   write(‘one uer file numbers k=’);
   readln(k);
   new(p2);
   for j:=1 to k do
      begin
      write(‘input     ufd--------name=’);
      readln(x);
      p2^.length;=s;
      p2^.next:=nil;
      ufd:=p2;  new(p2);
      ufd^.next:=p2;
      end;
   print;
writeln(‘input uer name you wantto opearate’);
   readln(x);I:=1;
   whilex<>mfd[I]^.uername do 
      begin
      if i>=n then
         begin
         writeln(‘not found user mfd filename’);
         writeln(‘input again mfd filename’);
         goto 10
         end
      else 
   i:=i+1;
   end;
ufd:=mfd[I]^.next;
t:=fale; i1:=0;
while t<>true do
   begin
   writeln(‘--------------------------------------------------------’);
   writeln(‘    1---create          2---open           ’);
       writeln(‘    3---delete          4---close           ’);
       writeln(‘    5---read           6--- write           ’);
       writeln(‘    7---end                              ’);
       writeln(‘---------------------------------------------------------’);
   readln(s);
       case s of
          1:pcreate;
          2:popen;
          3:pdelete;
          4:pclose;
          5:pread;
          6:pwrite;
          7:pbye;
       end;
    end.