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Line 62: ===High-level languages=== Some compiled languages explicitly permit self-modifying code. For example, the ALTER verb in [[COBOL]] may be implemented as a branch instruction that is modified during execution.<ref name="MicroFocus_ALTER"/> Some [[batch file\|batch]] programming techniques involve the use of self-modifying code. [[Clipper (programming language)\|Clipper]] and [[~~SPITBOL compiler\|~~SPITBOL]] also provide facilities for explicit self-modification. The Algol compiler on [[Burroughs ~~large~~Large ~~systems~~Systems\|B6700 systems]] offered an interface to the operating system whereby executing code could pass a text string or a named disc file to the Algol compiler and was then able to invoke the new version of a procedure. With interpreted languages, the "machine code" is the source text and may be susceptible to editing on-the-fly: in [[SNOBOL]] the source statements being executed are elements of a text array. Other languages, such as [[Perl]] and [[Python (programming language)\|Python]], allow programs to create new code at run-time and execute it using an [[eval]] function, but do not allow existing code to be mutated. The illusion of modification (even though no machine code is really being overwritten) is achieved by modifying function pointers, as in this JavaScript example:

Self-modifying code: Difference between revisions