Melody - Chromatic Scale

A chromatic scale is scale in which all  notes are a half step (semitone) apart. It consists of all 12 notes. Ascending chromatic scales use sharps for black piano keys. Descending chromatic scales use flats for black piano keys.

 When ascending (going up) the chromatic scale, we use sharps:

When descending (going down) the chromatic scale, we use flats:

Here is C Chromatic Scale ascending and descending: