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 http://stackoverflow.com/questions/472103/lower-case-k-in-cocoa/472118#472118.

Answer 2

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

Answer 3

According to this page from the Apple docs, k just indicates that the value is a constant.