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MichaelMaggs (talk | contribs) Adding short description: "Computer designed to run a specific language" |
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{{Short description|Computer designed to run a specific language}}
A '''high-level language computer architecture''' ('''HLLCA''') is a [[computer architecture]] designed to be targeted by a specific [[high-level programming language]] (HLL), rather than the architecture being dictated by hardware considerations. It is accordingly also termed '''language-directed computer design''', coined in {{harvtxt|McKeeman|1967}} and primarily used in the 1960s and 1970s. HLLCAs were popular in the 1960s and 1970s, but largely disappeared in the 1980s. This followed the dramatic failure of the [[Intel 432]] (1981) and the emergence of [[optimizing compiler]]s and [[reduced instruction set computer]] (RISC) architectures and RISC-like [[complex instruction set computer]] (CISC) architectures, and the later development of [[just-in-time compilation]] (JIT) for HLLs. A detailed survey and critique can be found in {{harvtxt|Ditzel|Patterson|1980}}.
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==Definition==
There are a wide variety of systems under this heading. The most extreme example is a Directly Executed Language (DEL), where the [[instruction set architecture]] (ISA) of the computer equals the instructions of the HLL, and the [[source code]] is directly executable with minimal processing. In extreme cases, the only compiling needed is [[Tokenization (lexical analysis)|tokenizing]] the source code and feeding the tokens directly to the processor; this is found in [[stack-oriented programming language]]s running on a [[stack machine]]. For more conventional languages, the HLL statements are grouped into instruction + [[Parameter (computer programming)|arguments]], and [[Infix notation|infix]] order is transformed to [[Substring|prefix]] or [[Reverse Polish notation|postfix]] order. DELs are typically only hypothetical, though they were advocated in the 1970s.<ref>See Yaohan Chu references.</ref>
In less extreme examples, the source code is first parsed to [[bytecode]], which is then the [[machine code]] that is passed to the processor. In these cases, the system typically lacks an [[Assembly language|assembler]], as the [[compiler]] is deemed sufficient, though in some cases (such as Java), assemblers are used to produce legal bytecode which would not be output by the compiler. This approach was found in the [[Pascal MicroEngine]] (1979), and is currently used by Java processors.
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