Design Patterns & Refactoring: Dictionaries/ Encyclopedia

Digital Library of Mathematical Functions

Digital handbook of mathematical functions with formulas, graphs, and mathematical tables. Managed by the National Institute of Standards and Technology.

FOLDOC  

It includes definitions of acronyms, jargon, programming languages, tools, architecture, operating  etc.

Computer Desktop Encyclopedia 

CDE has been around and evolving since 1978.  This online version contains over 25,000 technical terms and phrases, 3,000 images, and 40,000 cross references,  It covers all aspects of computing, from chips to supercomputers and from command examples to mini-tutorials. It's free and there's no advertising.

Webopedia 

Webopedia is an online dictionary of computer- and Internet-related terms.

50+ Killer Online Resources for Computer Science Students Computer science students are lucky because the Internet is like a living textbook, full of information and advice for their field. Many professors, experts, and other people skilled in computer science have created essays, tutorials, and resource points, all designed to make your life easier. We’ve compiled over 50 of the best here.