From Free Pascal wiki
% (pronounced "percent sign") is used in Pascal:
- it indicates a binary numeral expression/number.
The percent sign also appears in Lazarus IDE directives of the form
program simple_binary_digit; var b:byte; begin b := %1010011; writeln (b); writeln (binStr(b,8)); writeln ; writeln ('Press [Enter] to finish'); readln; end.
The output prints as follows:
83 01010011 Press [enter] to finish