program bdemo(output); {demonstrates binary file I/O in Pascal,
                          using external C routines to help out}
label 9999;
const namelength=100;
type byte=-128..127;
 bytefile=packed file of byte;
 UNIXfilename=packed array[1..namelength] of char;
var fname:UNIXfilename;
 bfile:bytefile;
 k,l:integer;
#include "bdemo_ext.h"
procedure printstatus(n:integer);
var x:byte;
begin if testeof(bfile) then writeln('Byte ',n:1,' is EOF')
else begin read(bfile,x); writeln('Byte ',n:1,' is ',x:1);
  end;
end;
begin if argc=1 then {no file name argument given on command line}
  begin writeln('Creating test file btest');
  fname:='btest';
  if not testwriteaccess(fname) then
    begin writeln('I couldn''t create it!'); goto 9999;
    end;
  rewrite(bfile,fname);
  for k:=-128 to 127 do write(bfile,k);
  end
else begin argv(1,fname); k:=1;
  while (k<namelength)and(fname[k]<>' ') do k:=k+1;
  writeln('Examining file ',fname:k,':');
  end;
if not testreadaccess(fname) then
  begin writeln('I couldn''t read it!'); goto 9999;
  end;
reset(bfile,fname);
l:=flength(bfile);
writeln('The file is ',l:1,' bytes long');
printstatus(1);
if l>0 then
  begin printstatus(2);
  if l>1 then
    begin movetobyte(bfile,l-2); printstatus(l-1);
    end;
  movetobyte(bfile,l-1); printstatus(l);
  printstatus(l+1);
  movetobyte(bfile,l div 2); printstatus(l div 2 + 1);
  movetobyte(bfile,1); printstatus(2);
  end;
9999:end.