Y Windows – The Y Windows, also known as Y Window System, is a windowing system, consisting of a window server and a client library for writing applications, written by Mark Thomas. It is intended to be a successor to the X Window System. It differs from the X Window System in having an integrated widget set and ground-up support for things like an alpha channel, which allows transparent or translucent windows.
Yacc: Yet Another Compiler Compiler – Yacc, abbreviated from “Yet Another Compiler Compiler”, is a Unix system tool program for generating C or C++ code for a parser. Yacc is a command-line tool that accepts a grammar description (in a text file) as input and generates the code for a parser for that grammar as output. Parsers are useful in many systems other than just compilers, such as for reading the contents of a configuration file stored in a system’s flash memory. Yacc was developed by Stephen C. Johnson at AT&T for the Unix operating system. Later compatible programs were written, such as Berkeley Yacc, GNU bison, MKS yacc and Abraxas yacc. Each offers slight improvements and additional features over the original Yacc, but the concept has remained the same. Yacc has also been rewritten for other languages, including Ratfor, EFL, ML, Ada, Java, and Limbo.
YafRay: Yet Another Free Raytracer – YafRay, abbreviated from “Yet Another Free Raytracer”, is an open source ray tracing program that uses an XML scene description language. It has recently been integrated into, and is often used to render scenes made in, the 3D modelling software Blender.