In keeping with the major scale sequence of tone-tone-semitone-tone-tone-tone-semitone, the A major scale contains C# , F# , and G# notes. This same scale/pattern can be played starting on the A note at the 12th fret of the 3rd string, all notes being one octave higher.
The major scale pattern can be played by starting at any note on the 3rd or 4th string. The note you start on will be the root note of the scale. For example, if you start on the Eb note at the 6th fret of the 3rd string you will be playing the Eb major scale: