The diatonic scale consists of five whole steps and two half steps. The half steps lie between either two or three whole steps, and the whole pattern repeats in each octave.
The diatonic scale is ancient in origin. For centuries, it was the basis of all music in the Western hemisphere. (See References 3)
The diatonic major scale consists of seven pitches. In the seven pitches of "do re mi fa so la ti do", the two "do" pitches are the same, but an octave apart.
The half steps, or pitches between the natural pitches, are referred to by using the notes' letter names plus "sharp" for a half-step higher pitch, and "flat" for a half-step lower pitch.
The notes of the lines of the treble clef staff can be remembered with the memory device of "Every Good Boy Does Fine" (EGBDF). The note on the spaces of the treble clef staff can be remembered because the notes on the spaces spell out the word "FACE". A memory device for the notes on the bass clef lines is "Good Boys Don't Fight Anyone" (GBDF), and for the notes on the bass clef spaces, "All Cows Eat Grass" (ACEG). (See References 1)