An octave is the range of eight notes of a major scale. The first note and last note of a major scale always have the same name. In the C major scale the distance from the lowest C to the C note above it is one octave (eight notes).
The C major scale over one octave is notated as follows:
Play the C major scale with the left hand fingering as indicated.
All major scales have this pattern of tones and semitones.