PLDI meaning in Academic & Science ?

Programming Language Design and Implementation (PLDI) is one of the ACM SIGPLAN's most important conferences. The precursor of PLDI was the Symposium on Compiler Optimization, held July 27–28, 1970 at the University of Illinois at Urbana-Champaign and chaired by Robert S. Northcote. That conference included papers by Frances E. Allen, John Cocke, Alfred V. Aho, Ravi Sethi, and Jeffrey D. Ullman. The first conference in the current PLDI series took place in 1979 under the name SIGPLAN Symposium on Compiler Construction in Denver, Colorado. The next Compiler Construction conference took place in 1982 in Boston, Massachusetts. The Compiler Construction conferences then alternated with SIGPLAN Conferences on Language Issues until 1988, when the conference was renamed to PLDI. From 1982 until 2001, the conference acronym was SIGPLAN 'xx. Starting in 2002, the initialism became PLDI 'xx, and in 2006 PLDI xxxx.