A numerical control apparatus incorporating a programmable controller and capable of displaying a comment in a plurality of languages with a single sequence program and of displaying a comment in a maintenance screen in a manner suited to the screen. The sequence program has a signal information area stored at its addresses with comments on signals or on the sequence program, each comment being written in a plurality of languages. Languages serving as display (language) attributes of each comment are also stored. In displaying a ladder diagram after the setting of language (for example, English) is completed, as for an address for which there is any comment of the preset language (English), such comment (second comment written in English) is displayed. Comments displayed in a desired language make it easy to perform the maintenance and management of the programmable controller and the numerical control apparatus.