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[[File:Dosbox 001.png|thumb|right|MS DOS's ''DEBUG'' command wasis line-oriented, whereas CodeView wasis full-screen oriented]]
'''CodeView''' wasis a standalone [[debugger]] created by [[David Norris (Microsoft)|David Norris]] at [[Microsoft]] in 1985 as part of its development toolset.<ref name=CV3x>{{cite magazine |magazine=[[WinWorld]]
|title=WinWorld: CodeView 3.x
|url=https://winworldpc.com/product/codeview/3x}}</ref> It originally shipped with Microsoft C 4.0 and later. It also shipped with [[Visual Basic]] for [[MS-DOS]], Microsoft Basic PDS, and a number of other Microsoft language products.<ref name=CV87>{{cite book
==Overview==
When running, CodeView would presentpresents the user with several [[window (computing)|windows]] that couldcan be tiled, moved, sized and otherwise manipulated via the keyboard or mouse, with CodeView 4.x providing a richer interface. Some of the windows includedinclude:
* Code window - the code window showed the currently debugged code in its [[source code]] context.
* Output window - a window showing startup operations and debugging information relating to breakpoints,<ref name=CV87/>{{rp|p. 157}} hardware breaks (interrupt 0 and 3), etc.
===supported features===
* 386 mode - CodeView supported 8086, 80286 and 80386 and later processors. 386 enhanced mode wasis activated by a menu option, allowing for 32-bit registers and disassembly.
* Monochrome monitor support - CodeView supportedallows debugging on either a single color (CGA, EGA or VGA) monitor with page/memory swapping between the user application and the CodeView screen, or through a feature which utilizedusing a separate monochrome monitor. The monochrome monitor existedexists in memory address space 0xb0000, while the color monitor existedexists at 0xb8000 for text and 0xa0000 for graphics. Use of the monochrome monitor with its separate memory address space allowedallows debugging graphics applications without affecting the display, as well as all text modes. Monochrome monitormonitors support wasare limited to 25 lines, whereas color monitors could utilizeallow 25, 43 or 50 line mode, allowing for more information on the screen at the same time.
Creating symbolic debugging output, which allowedallows memory locations to be viewed by their programmer-assigned name, along with a program database showing the source code line related to every computer instruction in the binary executable, wasis provided forenabled by the command line switch -Zi given to the compiler, and -CO given to the linker. Variants like -Zs and -Zd providedprovide lesser information, and smaller output files which, during the early 1990s, were important due to limited machine resources, such as memory and hard disk capacity. Many systems in those days had 8MB of memory or less.
CodeView supportedhandles all program models, including TINY, SMALL, COMPACT, MEDIUM, LARGE and HUGE, with TINY (DOS-based .COM files) having their symbolic debugger information stored in a separate file, with all of the other .EXE formats containing the symbolic information directly inside the executable. This often introduced a notable size increase, and it therefore became desirable for some developers to use #pragma switches within their C (and later C++) source code to prevent the majority of the application from having symbolic output, and instead limiting that output to only those portions which required it for current debugging.
CodeView version 3.x and 4.x introduced various transport layers, which removed some of the memory space limitations to this form of symbolic debugging. Typically the debugger would runruns in the lower 640KB memory space alongside the application being debugged, which greatly decreaseddecreases the amount of memory available to the application being debugged. The transport layer allowedallows only a stub to exist in main memory, while the bulk of the debugger code residedresides in EMS or XMS (memory above the 1MB barrier, or outside of the normal 0KB - 640KB address space typically used by DOS programs). CodeView also came with a CVPACK command-line utility, which couldcan reduce the size of the CodeView-generated information internally, while still retaining full symbolic access to data.
==Visual C++ support==
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