Original author(s)David Norris
Initial release1985; 39 years ago (1985)
Operating systemMS-DOS

CodeView is a standalone debugger created by David Norris at Microsoft in 1985 as part of its development toolset.[1] 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.[2] It was one of the first debuggers for MS-DOS to be full-screen oriented, rather than line-oriented (as Microsoft's predecessors DEBUG and SYMDEB or Digital Research's SID).


When running, CodeView presents the user with several windows that can be tiled, moved, sized and otherwise manipulated via the keyboard or mouse, with CodeView 4.x providing a richer interface. Some of the windows include:


Creating symbolic debugging output, which allows 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, is enabled by the command line switch -Zi given to the compiler, and -CO given to the linker. Variants like -Zs and -Zd provide 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 handles 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 runs in the lower 640KB memory space alongside the application being debugged, which greatly decreases the amount of memory available to the application being debugged. The transport layer allows only a stub to exist in main memory, while the bulk of the debugger code resides in EMS or XMS (memory above the 1 MB barrier, or outside of the normal 0 KB - 640 KB address space typically used by DOS programs). CodeView also came with a CVPACK command-line utility, which can reduce the size of the CodeView-generated information internally, while still retaining full symbolic access to data.

Visual C++ support

Microsoft released Visual C++ 1.0 with CodeView functionality integrated directly into a single programming environment, known as the Integrated Development Environment (IDE) -- though CodeView was still available in the 16-bit versions of Visual C++. QuickC and a number of other development tools in the 'Quick' series also supported this move to a single-source IDE, what became the precursor to the modern Visual Studio developer environment, as well as the model for countless other developer toolsets.

This integration was seen by many developers as a more natural way of developing software because both coding and debugging could be handled without switching programs or context, and all from the same logical location (even though internally many separate programs were running to support editing, compiling and debugging). As a result, most development tools and/or platforms offer similar products or features.

Today, the debugger is considered an integrated and essential part of the Microsoft Visual Studio family of products, and owes its true roots to CodeView, and the enhancements seen in version 4.x specifically.


Another debugging product available from Microsoft in the mid-1980s was SYMDEB.[3]

It had over 30 commands, and was described by PC Magazine as a step up from DEBUG.[4] Codeview in turn was described as "a fullscreen SYMDEB".[5][6]

See also


  1. ^ "CodeView 3.x". WinWorld.
  2. ^ a b Microsoft Macro Assembler 5.1 - Microsoft CodeView and Utilities. Microsoft Corporation. 1987. p. 157. Document No. 4108-40010-500-R03-1287.
  3. ^ Par, Jeff (2018-02-25). "A Short History of SYMDEB". PCjs Machines. Retrieved 2019-05-19.
  4. ^ "SYMDEB: A step up from Debug". PC World. 1986-10-14. p. 296.
  5. ^ "SYMDEB". PC Magazine. Vol. 5, no. 17. Ziff Davis, Inc. 1986-09-30. p. 38. ISSN 0888-8507.
  6. ^ "MS C 4.0 Documentation Added".
  7. ^ "CodeView Type Records — LLVM 13 documentation". Retrieved 2021-12-19.

Further reading