What does the 'k' prefix indicate in Apple's APIs?

Question

I've run across many examples of Core Foundation variables named k + someVariableNameHere or k + APILibraryName(2Char) + someVariableNameHere. What does this prefix K indicate?

Examples include:

kGLPFAStereo
kCollectionLockBit
kSetDebugOption

Answer 1

The k means constant in hungarian notation... see Lower case "k" in Cocoa.

Answer 2

This is a naming convention from the early days of macintosh programming. It indicates a constant.