Just to recap the last section tones & semi-tones the position of the semi-tone intervals in scales determine the quality of the scale i.e. whether it is major, minor (natural, harmonic, melodic) etc. In major scales the semi-tones fall between the 3rd and 4th degrees and the 7th and 8th (marked on the illustration with slurs - they are the little curved lines) C major has no sharps or flats in the key signature as does its 'relative' A minor All major scales have a relative minor - you can find it by counting down 3 semi-tones i.e. from C - B=1 Bb=2 A=3
 
Summary:
C major has no sharps (#) or flats (b) in the key signature C-D-E-F-G-A-B-C The semitones fall between the 3rd and 4th degrees (E-F) and the 7th and 8th (B-C) The final semitone creates the 'finished effect' of the scale


Listen to C major (roll mouse over image)