Since this is a piano-related program, a brief understanding of some of the common terms used in this context is required.

In this section, we will use this figure as a reference:

The keyboard of a piano comprises a set of 12 keys (seven white and five black keys), which forms what is called a chromatic scale. This pattern of 12 keys repeats over and over again totaling up to 88 keys on a standard piano. The pattern repeats twice in the preceding image (C1 to B1 and then C2 to B2).

The distance between any two adjacent keys is called a semitone. Please take note of this term as we will define all piano-related rules using semitones—a measure of distance between keys. An interval of two semitones is called a whole tone. We will not bother with whole tones as far as our program is concerned.

The white keys of the piano are labeled by note names A to G. However, as per convention the counting of notes begins at C. C is the first white key just before the set of two black keys. The names of white keys are marked on the keys and the names of black keys are marked above them.

Since there are multiple sets of 12 keys they are differentiated among themselves by appending a number after them. For example, C1 is the first white key, while C2 is the key at the same position, but an octave higher. The black key just next to C is called C sharp (C#). Since it is also just before the key D it has another name—D flat ( D♭). We will, however, stick with calling all black keys by using the sharp symbol (#). Since the notes E and B do not have any sharp keys they are not immediately followed by any black key.