Y++
An Object-Oriented analysis and design approach.

yacc
Yet Another Compiler Compiler. A parser generator for UNIX by S.C.Johnson

YACL
Yet Another Class Library

Yellow Pages (YP)
See Network Information Service (NIS)

YP
See Network Information Service (NIS)

YP
Yellow Pages: a name server in NFS to link clients desiring a service with servers who can provide it.

YSM
Yourdon Structured Method