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Symbolic Optimal Assembly Program
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<p>The Symbolic Optimal Assembly Program (SOAP) is an <a href="/facts/Assembler_(computing)/7XuV0cla">assembler</a> for the <a href="/facts/IBM_650/l5mCAMIF">IBM 650</a> Magnetic Drum Data-Processing Machine, an early <a href="/facts/Computer/SQe1aK05">computer</a> first used in 1954. It was developed by Stan Poley at the IBM <a href="/facts/Thomas_J._Watson_Research_Center/XfGnAzRW">Thomas J. Watson Research Center</a>. SOAP is called "Optimal" (or "Optimum") because it attempts to store generated instructions on the <a href="/facts/Drum_memory/yul0r8nG">storage drum</a> to minimize the <a href="/facts/Access_time/Ckb7x4f6">access time</a> from one instruction to the next. SOAP is a <a href="/facts/Multi-pass_compiler/sfDsPLFI">multi-pass</a> assembler, that is, it processes the <a href="/facts/Source_program/o9J6Jv23">source program</a> more than once in order to generate the <a href="/facts/Object_program/VSst9eLA">object program</a>. </p><p>The first version of SOAP was succeeded by SOAP II in 1957, which supported additional hardware features such as <a href="/facts/Index_register/pdhWVmHA">index registers</a> and <a href="/facts/Magnetic_core_memory/4TFIXSNd">magnetic core memory</a>, then SOAP IIA in 1958, SOAP 2L, SOAP 2L Tape, SOAP 4000, and SOAP 42 in 1961. SOAP was used as a backend to the <a href="/facts/FOR_TRANSIT/Uf390FCp">FOR TRANSIT</a> compiler in 1957. </p><p><a href="/facts/Donald_Knuth/GozNzDM6">Donald Knuth</a> independently produced versions named SOAP III in 1958 and SUPERSOAP in 1959 at Case Institute of Technology, now part of <a href="/facts/Case_Western_Reserve_University/S0xlUbTM">Case Western Reserve University</a> in <a href="/facts/Cleveland%2c_Ohio/rQb7qveu">Cleveland, Ohio</a>. The US <a href="/facts/National_Bureau_of_Standards/gr9Fnh85">National Bureau of Standards</a>, under the direction of Herbert Howe, also wrote a version of SOAP, called ISOPAR, said to significantly improve optimization. </p>