MIDI note numbers are the unique numbers assigned to each note in the MIDI system. The MIDI numbering scheme uses 7 bits to identify all the notes. This means there are 128 notes (27) that can be assigned in MIDI. However, knowing which note is which is not always straightforward.
The MIDI specification, maintained by the MIDI Manufacturers Association, tells us that middle C is MIDI note number 60. All other notes are relative to this one. Therefore, MIDI note number 69, used for 440Hz tuning, should be the A above middle C (supposing an equal temperament tuning). However, the specifications does not say which one is middle C. It turns out that various manufacturers place this middle C at different octaves. It usually is C3, C4 or C5.
In the case of Logic Studio, middle C is C3. This means that MIDI note number 0 is C-2 and that the highest note possible is G8 (using MIDI note number 127). This is usually not a problem as all most MIDI devices can usually be transposed up or down easily. It becomes a problem when you work in a complex project where sounds have not been defined for all 10 octaves and you hit a note and hear nothing… Yep, this is what happened to me. Therefore, as an easy reference, I am posting here the codes as used in Logic Studio 9.