C-sharp major

C major (or C-sharp major) is a major scale based on C. Its key signature has seven sharps.
Its relative minor is A minor, and its parallel minor is C minor. Its enharmonic equivalent is D major.
When a harp is tuned to C-sharp major, it has all its pedals in the bottom position. Because all the strings are made shorter in this way, it makes it less resonant.
Most composers prefer to use the enharmonic equivalent D-flat major because it has just five flats. However, Johann Sebastian Bach actually chose C-sharp major for Prelude and Fugue No. 3 in both books of the "Well-Tempered Clavier". In Hungarian Rhapsody No. 6, Franz Liszt changes key from D-flat major to C-sharp major near the beginning of the piece. Maurice Ravel used C-sharp major as the tonic key of "Ondine" from his piano suite "Gaspard de la nuit". 
Louis Vierne used C-sharp major in the final piece of Messe solennelle.