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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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