The G major scale starts and ends on the note G and contains an F sharp (F#) note. The following example demonstrates the two octaves of the G major scale. Notice that the G major scale has the same patterns of tones and semitones as the C major scale.
In a major scale the interval between the 3rd to 4th note and the 7th to 8th notes is a semitone (1 fret). In the G major scale, to keep this pattern of tones and semitones correct, an F#) note must be used instead of an F note.