RadioButtons hold a boolean value of either true or false. Normally RadioButtons are placed in groups. RadioButtons are used when there is a setting that needs options that are mutually exclusive. If a single setting is independent, then a CheckBox should be used.

RadioButtons hold a boolean value in the RadioButtons’s Checked Property:

RadioButton1.Checked := True

RadioButton1.Checked := False

Video Tutorial: Free Pascal Tutorial 20 - RadioButtons - Lazarus (8:32)

The code for Tutorial 18, 19, 20 & 21 is found on Tutorial 21’s Page