Finding prime numbers

The program finding prime numbers in the range specified by the user.
Programming language: FreePascal.

Code:
Program Prime;
Var
i, j, a, b:integer;
begin
  Writeln('Enter the first number of the range: ');
  Readln(a);
  Writeln;
  Writeln('Enter the last number of the range: ');
  Readln(b);
  WriteLn;
  Writeln('prime numbers: ');

    for i:=a to b do
    begin
      for j:=2 to i do
       if (i mod j)=0  then
          if (i=j) then
          write(i,' ')
          else
          j:=i;

    end;
  Readln;
end.