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Y2K

(as letters) abbr. A predicted dramatic global embedded systems failure that never materialized. Short for Year 2000. Most embedded systems programmers correctly understood that the designers of elevators and sewer level monitors do not go to the trouble of including a calendar or of comparing dates and that, if they do, this date information is typically used only for event logging and not actual decision making.

Many Chicken Little outsiders, however, correctly grokking both the Y2K database problem lingering in legacy COBOL programs run by large private and government institutions and the increasing ubiquity of processors at the heart of almost everything that plugs into the wall or eats batteries, predicted a virtual doomsday, bought gold ingots or generators, and filled their bathtubs with water in anticipation of the nonevent of the century.

yacc

(yak) N. A tool for generating C or C++ code for a parser. Short for Yet Another Compiler Compiler. Once an stream of data has been converted into tokens by a lexical scanner, such as lex, the relationship between those tokens needs to be established. The possible token orders for a language is called its grammar. 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.

yield

1. v. To offer use of the processor to another thread that is ready to run.

2. n. The percentage of good die on a wafer. IC vendors test each die, with the sure knowledge that some percentage of them will not pass. Mature manufacturing processes with smaller chips give high yields; very dense parts or those made with new processes could result in yields less than 50%.