Fender Bass Necks

[Hobbayne]

Hi all, sorry to be ignorant, but I have seen guitars advertised on ebay for sale, and folks talking here about Fenders with C shape or A shape necks!
I thought the necks were standard for Fender basses?
What do these letters mean exactly?
I have a 1977 Fender Precision can someone tell me what neck is on this? at least I can pretend I know what I,m talking about in the local guitar shop!

Sorry about Pic quality, crappy iphone camera

[BlountEdge]

Go here:

http://home.provide.net/~cfh/fender.html

Scroll down to neck back shapes, followed by neck widths.