Can't Memorise Computer-Industry Acronyms) PCN – (s) Pitcairn Islands (ISO 3166 trigram) PCP (p) phencyclidine Pneumocystis jiroveci pneumonia (formerly Pneumocystis carinii) (i) Probabilistically Checkable Proof PCPI – Physician Consortium for Performance Improvement (AMA) PCR – (i) Polymerase chain reaction PCSSD - (p) Pulaski County Special School District PCT (i) Pacific Crest Trail Patent Cooperation Treaty PCTE (i) Portable Common Tool Environment (i) Punjab College of Technical Education PCZ – (s) Panama Canal Zone (ISO 3166 trigram; obsolete 1980) PD Pd – (s) Palladium PD (i) per diem (Latin: (calculated) by the day) Point of Departure Police Department Postal District Potential Difference Principal Deputy Privatdozent Public domain PD – (i) Product Director—Example: CERDEC Product Director C4ISR and Network Modernization PDA (i) Personal Digital Assistant Predicted Drift Angle Public Display of Affection Push-Down Automaton PDD (i) Past Due Date Presidential Decision Directive PDF (i) Panama[nian] Defense Forces (abolished 1990) Portable Document Format Principal Direction of Fire PDG (i) President Director General Product Development Group PDL (i) Premier Development League, a former name of the U.S. minor soccer league now known as USL League Two Pure Dumb Luck (Texan punk band) PDN – (i) Pull-Down Network PDP (i) Programmable Data Processor Performance Development Plan PDQ (i) Pre-Defined Queries (Siebel packages) Pretty Damn Quick PDRY – (i) People's Democratic Republic of Yemen (obsolete since 1990) PDT – (i) Pacific Daylight [Saving] Time (UTC-7 hours) PDU (i) Police Dog Unit Power Distribution Unit Protocol Data Unit PDVSA – (a/i) Petróleos de Venezuela, S.A. (Spanish, "Venezuelan Petroleum Company") PE PE – Professional Engineer PE – (s) Ice Pellets (old style METAR Code) – Peru (ISO 3166 and FIPS 10-4 country code digram) – (i) Physical Education – Premature Ejaculation – (s) Prince Edward Island (postal code) – Price to Earning ratio (used for equity shares) – Plant Extract PEBCAC – (a) Problem Exists Between Chair and Computer (IT help desk in-joke) PEBKAC – (a) Problem Exists Between Keyboard and Chair (ditto) PEEK – (i) PolyEtherEtherKetone PEET – (a) Partnerships for Enhancing Expertise in Taxonomy PEGIDA – (a) Patriotische Europäer gegen die Islamisierung des Abendlandes (German, "Patriotic Europeans Against the Islamization of the West") PEI – (i) Prince Edward Island – PolyEtherImide PEK – (i) PolyEtherKetone PEMDAS - The order of operations in math (Parentheses, Exponents, Division, Multiplication, Addition, Subtraction) PEN (s) Peruvian sol (ISO 4217 currency code) (i) Poets, Essayists and Novelists, the original meaning of