between console and the VAX console interface. Unlicensed clones The PDP-11 was sufficiently popular that many unlicensed PDP-11-compatible minicomputers and microcomputers were produced in Eastern Bloc countries. Some were pin-compatible with the PDP-11 and could use its peripherals and system software. These include: SM-4, SM-1420, SM-1600, Electronika 100-25, Electronika BK series, Electronika 60, Electronika 85, DVK, UKNC, and some models of the SM EVM series (in the Soviet Union). SM-4, SM-1420, IZOT-1016 and peripherals (in Bulgaria). MERA-60 in Poland. SM-1620, SM-1630 (in East Germany). SM-4, TPA-1140, TPA-1148, TPA-11/440 (in Hungary). SM-4/20, SM 52-11, JPR-12R (in Czechoslovakia). CalData – Made in US, ran all DEC OSes. CORAL series (made at ICE Felix in Bucharest) and the INDEPENDENT series (made at ITC Timișoara) running the RSX-11M operating system (in Romania). The CORAL series had several models: the CORAL 4001 was roughly equivalent to the PDP-11/04, the CORAL 4011 was a PDP 11/34 clone, while the CORAL 4030 was a PDP-11/44 clone. These were used in state-owned companies and in public universities, originally operated with punched cards, later through video terminals like the Romanian DAF-2020, to teach FORTRAN and Pascal, until replaced by IBM PC compatibles, starting in 1991. Systime Computers models 1000, 3000, 5000 – OEM agreement for sales in the UK and Western Europe, but disputes originated over both intellectual property infringement and indirect sales to the Eastern Bloc. Operating systems Several operating systems were available for the PDP-11. From Digital Commercial Operating System BATCH-11/DOS-11 CAPS-11 (Cassette Programming System) CHRONIC Hierarchical Storage Controller executive GAMMA-11 DSM-11 IAS P/OS RSTS/E RSX-11 RT-11 TRAX (Transaction Processing system) Ultrix-11 From third parties ANDOS CSI-DOS DEIMOS (University of Edinburgh) DEMOS (Soviet Union) Duress (University of Illinois at Urbana–Champaign/Datalogics) LOS/C, a small unitasking system written by BRL for the BRL routers and the I/O controller for the Denelcor HEP MERT Micropower Pascal MK-DOS MONECS MTS (Multi-Tasking System written in RTL/2 by SPL) MUMPS MUSS-11 PC11 (Decus 11-501/Pilkington) polyForth, Forth Inc.'s Forth for the PDP-11 ROSTTP (Realtime Operating System for Terminal Teletype Processing/Simpact) SHAREeleven, SHAREplus Solo by Per Brinch Hansen Sphere (Infosphere – Portland Oregon 1981–87) Softech Microsystems UCSD System with UCSD Pascal TRIPOS TSX-Plus Unix (many versions, including Version 6 Unix, Version 7 Unix, UNIX System III, and 2BSD) Xinu OS for instructional purposes Venix (implementation/port of Unix developed by VenturCom) Communications The DECSA communications server was a communications platform developed by DEC based on a