Example of Pascal record with or without variant

a.pas

program a;

type xxx = record
       a,b,c: char;
     end;

var f: file of xxx;
    v: xxx;

begin
  assign(f,'a.dat');
  rewrite(f);
  v.a := 'a';
  v.b := 'b';
  v.c := 'c';
  write(f,v);
  close(f);
end.

b.pas

program b;

type xxx = record
       case byte of
         0: (a: char);
         1: (b: char);
         2: (c: char);
     end;

var f: file of xxx;
    v: xxx;

begin
  assign(f,'b.dat');
  rewrite(f);
  v.a := 'a';
  v.b := 'b';
  v.c := 'c';
  write(f,v);
  close(f);
end.