File format for the exchange of resolution-independent, pixel-based (bitmapped) images, intended for very high quality moving image content for theatrical distribution; DPX masters provide the input for film recording (digital images back to film for projection) or D-Cinema digital projection systems.
Most modern pianos have a row of 88 black and white keys (52 white keys for the notes of the C Major scale (the notes C, D, E, F, G, A and B) and 36 shorter black keys, which are raised above the white keys, and set further back on the keyboard.
If you play in a key, it means you play a specific selection of notes, and not others. Every key has 7 notes. If you imagine the white notes on the piano, those are the ones which are in the key of C major. The C major scale (a scale is what you get when you play the notes in a key in order - up or down) starts at C and goes C, D, E, F, G, A, B, then back to C. The black notes on the keyboard are the sharps and flats.