MacsBug is a low-level (

assembly language In computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence be ...

/machine-level)

debugger A debugger or debugging tool is a computer program used to software testing, test and debugging, debug other programs (the "target" program). The main use of a debugger is to run the target program under controlled conditions that permit the pr ...

for the

classic Mac OS Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Macintosh family of personal computers by Apple Computer from 1984 to 2001, starting with System 1 and ending with Mac OS 9. The ...

operating system. MacsBug is an acronym for ''Motorola Advanced Computer Systems Debugger'', as opposed to ''Macintosh debugger'' (The Motorola 68000 Microprocessor is imprinted with the MACSS acronym). The original version was developed by Motorola as a general debugger for its

68000 The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector ...

systems.MACSbug 68000 Debugger User's Manual
Catalog entry,

Computer History Museum The Computer History Museum (CHM) is a museum of computer history, located in Mountain View, California. The museum presents stories and artifacts of Silicon Valley and the information age, and explores the computing revolution and its impact on ...

— it was ported to the Mac as a programmer's tool early in the project's development. MacsBug is invoked by hitting the Macintosh's " Programmer's Key" or, as it became later known, the "Interrupt Key" or by pressing "Command-Power". MacsBug offers many commands for disassembling, searching, and viewing data as well as control over

processor register A processor register is a quickly accessible location available to a computer's processor. Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write-only. ...

s. MacsBug is not installed by default with Mac OS, although every Macintosh since the Macintosh Plus includes a debugger in ROM known as MicroBug. Users who stumble into MacsBug by accident need only to enter G and press return to escape from MacsBug; however, MacsBug is not installed by default, requiring a system extension, so a typical user environment does not include it. However, it was occasionally installed by end users to provide very basic error recovery. As the classic Mac OS lacked

memory protection Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that ha ...

, "hard crashes" where an application crash simply froze the entire system weren't uncommon. With MacsBug installed, instead of an unresponsive system, the user would be dumped into MacsBug, where they could type ES to Exit to Shell (force quit the crashed application and return to the Finder) or RB for ReBoot, which restarted the system. Such recovery efforts were often not successful, with the only alternative a

hard reset A hardware reset or hard reset of a computer system is a hardware operation that re-initializes the core hardware components of the system, thus ending all current software operations in the system. This is typically, but not always, followed by b ...

. In Mac OS versions 7.5 and later, the presence of MacsBug is indicated at startup; it is present if the user sees the text ''Debugger installed'' (although, occasionally, this may indicate the presence of another piece of software loaded into the area of memory reserved for the debugger, instead). MacsBug was originally for the Motorola 68000 series of processors only. When Apple introduced the

Power Macintosh The Power Macintosh, later Power Mac, is a family of personal computers designed, manufactured, and sold by Apple Computer as the core of the Macintosh brand from March 1994 until August 2006. Described by ''MacWorld'' as "the most important te ...

in 1994, it was followed by an updated MacsBug that supported the

PowerPC PowerPC (with the backronym Performance Optimization With Enhanced RISC – Performance Computing, sometimes abbreviated as PPC) is a reduced instruction set computer (RISC) instruction set architecture (ISA) created by the 1991 Apple Inc., App ...

instruction set and architecture. The last version of MacsBug was 6.6.3, released September 14, 2000. This final version works with all of the machines released in the July–September timeframe of 2000, including the

Power Mac G4 The Power Mac G4 is a series of personal computers designed, manufactured, and sold by Apple Computer from 1999 to 2004 as part of the Power Macintosh line. Built around the PowerPC G4 series of microprocessors, the Power Mac G4 was marketed by ...

(uni- and multi-processor),

Power Mac G4 Cube The Power Mac G4 Cube is a Macintosh personal computer sold by Apple Computer, Inc. between July 2000 and 2001. Designed by Jonathan Ive, the Cube was conceived by Apple chief executive officer (CEO) Steve Jobs, who held an interest in a power ...

, the

iMac iMac is a family of all-in-one Mac desktop computers designed and built by Apple Inc. It has been the primary part of Apple's consumer desktop offerings since its debut in August 1998, and has evolved through seven distinct forms. In it ...

family (Ruby, Indigo, Sage, Graphite, and Snow), and the

iBook iBook is a line of laptop computers designed, manufactured, and sold by Apple Computer from 1999 to 2006. The line targeted entry-level, consumer and education markets, with lower specifications and prices than the PowerBook, Apple's higher-en ...

family (Indigo, Key Lime, and Graphite). 6.6.3 includes better support for debugging MP tasks, and fixes some serious bugs in the memory setting commands when used in

PCI PCI may refer to: Business and economics * Payment card industry, businesses associated with debit, credit, and other payment cards ** Payment Card Industry Data Security Standard, a set of security requirements for credit card processors * Pro ...

I/O space. It can also be used in

Classic A classic is an outstanding example of a particular style; something of lasting worth or with a timeless quality; of the first or highest quality, class, or rank – something that exemplifies its class. The word can be an adjective (a ''c ...

when running under Mac OS X, where it is invoked by pressing "⌘-⏏" (or "⌘-F12" on systems without an Eject key). Mac OS X allows programmers to use familiar MacsBug commands in

gdb The GNU Debugger (GDB) is a Software portability, portable debugger that runs on many Unix-like systems and works for many programming languages, including Ada (programming language), Ada, C (programming language), C, C++, Objective-C, Free Pasc ...

. This gdb plugin is included with the OS X Developer Tools, located in the directory /usr/libexec/gdb/plugins/MacsBug/. Third party alternatives to MacsBug included

ICOM Simulations ICOM Simulations, Inc. (later known as Rabid Entertainment) was a software company based in Wheeling, Illinois. It is best known for creating the MacVenture series of adventure games including ''Shadowgate''. Following the foundation in 1981 a n ...

' TMON which came with the

Darin Adler Darin Adler was the technical lead for Apple Computer's System 7 operating system release. During 1985–1987 he worked for ICOM Simulations as primary developer of the MacVenture game engine which ran Déjà Vu: A Nightmare Comes True, Uninvit ...

Extended User Area & Trap Discipline (allowing all documented Mac API parameters to be verified) and the fully symbolic

Jasik debugger The Jasik Debugger (or more correctly, The Debugger from Jasik Designs), was a debugger tool for the classic Mac OS. Pitched as a much more powerful alternative to Macsbug, it was a popular choice among professional Mac developers until the advent ...

, which was much more powerful, but harder to use due to the intricate and non-standard user interface.

Versions

* 1979 Motorola 68000 Design Module debugger * January 25, 1982 - Adapted by Rich Page for Lisa & Mac. * November 1, 1984 - Enhanced by Steve Capps. * May 13, 1985 - Version IV+ by Ken Krugler. * November 21, 1986 - Disassembler upgraded by Ira Reuben. * June 15, 1987 - Version 5.4 by Dan Allen. * March 31, 1988 - Version 5.6.1 by Dan Allen. * June 29, 1988 - Version 6.0 by Michael Tibbott. * April 20, 1989 - Version 6.1 by Michael Tibbott. * September 14, 2000 - Version 6.6.3.

References

External links

Apple's MacsBug page

{{DEFAULTSORT:Macsbug Apple Inc. software Debuggers Macintosh operating systems development Discontinued development tools Classic Mac OS programming tools