Editing Machine code (section)

==Readability by humans==
Machine code can be seen as a set of electrical pulses that make the instructions readable to the computer; it is not readable by humans,{{Sfn|Samuelson|1984|p=683}} with [[Douglas Hofstadter]] comparing it to examining the atoms of a [[DNA]] molecule.{{Sfn|Hofstadter|1979|p=[https://archive.org/details/godelescherbach00doug/page/290 290]}} However, various tools and methods exist to decode machine code to human-readable [[source code]]. One such method is [[disassembly]], which easily decodes it back to its corresponding assembly language [[source code]] because assembly language forms a one-to-one mapping to machine code.{{Sfn|Tanenbaum|1990|p=[https://archive.org/details/structuredcomput00tane/page/398 398]}}

Machine code may also be decoded to [[High-level programming language|high-level language]] under two conditions. The first condition is to accept an [[Obfuscation (software)|obfuscated]] reading of the source code. An obfuscated version of source code is displayed if the machine code is sent to a [[decompiler]] of the source language. The second condition requires the machine code to have information about the source code encoded within. The information includes a [[symbol table]] that contains [[debug symbol]]s. The symbol table may be stored within the executable, or it may exist in separate files. A [[debugger]] can then read the symbol table to help the programmer interactively [[debugging|debug]] the machine code in [[Instruction cycle|execution]].

* The [[SHARE Operating System]] (1959) for the [[IBM 709]], [[IBM 7090]], and [[IBM 7094]] computers allowed for an loadable code format named [[SQUOZE]]. SQUOZE was a compressed binary form of [[assembly language]] code and included a symbol table.
* Modern IBM mainframe [[operating system]]s, such as [[z/OS]], have available a symbol table named ''Associated data'' (ADATA). The table is stored in a file that can be produced by the [[IBM High-Level Assembler]] (HLASM),<ref name="IBM_ADA"/><REF name=IBM_ADATA /> IBM's [[COBOL]] compiler,<ref name="IBM_COBOL"/> and IBM's [[PL/I]] compiler,<ref>{{cite web |url=https://www.ibm.com/docs/en/epfz/6.1?topic=guide-sysadata-message-information |title=SYSADATA message information |work=Enterprise PL/I for z/OS 6.1 information}}</ref> either as a separate SYSADATA file or as ADATA records in a [[Generalized object output file]] (GOFF).<ref name=IBM_GOFF />
* [[Microsoft Windows]] has available a symbol table<ref name="Microsoft_Symbols"/> that is stored in a [[program database]] (<code>.pdb</code>) file.<ref name="Microsoft_PDB"/>
* Most [[Unix-like]] operating systems have available symbol table formats named [[stabs]] and [[DWARF]]. In [[macOS]] and other [[Darwin (operating system)|Darwin]]-based operating systems, the debug symbols are stored in DWARF format in a separate <code>.dSYM</code> file.