computer science

Ralf Brown's Interrupt List

Ralf Brown's Interrupt List is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ralf Brown's Interrupt List rather than just read about it. In short: Ralf Brown's Interrupt List (aka RBIL, x86 Interrupt List, MS-DOS Interrupt List or INTER) is a comprehensive list of interrupts, calls, hooks, interfaces, data structures, CMOS settings, memory and port addresses, as well as processor opcodes for x86 machines from the 1981 IBM PC up to 2000 (including many clones), most of it still applying to IBM PC compatibles today. It also lists some special function registers…

Key takeaways

Ralf Brown's Interrupt List belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ralf Brown's Interrupt List to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ralf Brown's Interrupt List from memory before moving on to harder problems.

Reference excerpt

Ralf Brown's Interrupt List (aka RBIL, x86 Interrupt List, MS-DOS Interrupt List or INTER) is a comprehensive list of interrupts, calls, hooks, interfaces, data structures, CMOS settings, memory and port addresses, as well as processor opcodes for x86 machines from the 1981 IBM PC up to 2000 (including many clones), most of it still applying to IBM PC compatibles today. It also lists some special function registers for the NEC V25 and V35 microcontrollers.

Overview The list covers operating systems, device drivers, and application software; both documented and undocumented information including bugs, incompatibilities, shortcomings, and workarounds, with version, locale, and date information, often at a detail level far beyond that found in the contemporary literature. A large part of it covers system BIOSes and internals of operating systems such as MS-DOS, OS/2, and Windows, as well as their interactions. It has been a widely used resource by IBM PC compatible system developers, analysts, as well as application programmers in the pre-Windows era. Parts of the compiled information have been used for and in the creation of several books on systems programming, some of which have also been translated into Chinese, Japanese and Russian. As such the compilation has proven to be an important resource in developing various closed and open source operating systems, including Linux and FreeDOS. The project is the result of the research and collaborative effort of more than 650 listed contributors worldwide over a period of 15 years, of which about 290 provided significant information (and some 55 of them even more than once). The original list was created in January 1985 by Janet Jack and others, and, named "Interrupt List for MS-DOS", it was subsequently maintained and mailed to requestors on Usenet by Ross M. Greenberg until 1986. As of October 1987, it is maintained by Ralf D. Brown, a researcher at Carnegie Mellon University's Language Technologies Institute. Information from several other interrupt listings was merged into the list in order to establish one comprehensive reference compilation. Over the years, Michael A. Shiels, Timothy Patrick Farley, Matthias R. Paul, Robin Douglas Howard Walker, Wolfgang Lierz and Tamura Jones became major contributors to the project, providing information all over the list. The project was also expanded to include other PC development-related information and therefore absorbed a number of independently maintained lists on PC I/O ports (by Wim Osterholt and Matthias R. Paul), BIOS CMOS memory contents (by Atley Padgett Peterson), processor opcodes (by Alex V. Potemkin) and bugs (by Harald Feldmann). Brown and Paul also conducted several systematic surveys on specific hard- and software details among a number of dedicated user groups in order to validate some info and to help fill some gaps in the list. Originally, the list was distributed in an archive named INTERRUP in various compression formats as well as in the form of diffs. The distribution file name was changed to include a version in the form INTERnyy (with n = issue number, and yy = 2-digit release year) in 1988. In mid 1989 the distribution used ZIP compression to keep its size manageable. When the archive reached the size of a 360 KB floppy in June 1991, the distribution split into several files following an `INTERrrp.ZIP` naming scheme (with rr = revision starting with 26 for version 91.3, and p = part indicator of the package starting with letter A). Officially named "MS-DOS Interrupt List" and "x86 Interrupt List" (abbreviated as "INTER") by its maintainer, the community coined the unofficial name "Ralf Brown's Interrupt List" (abbreviated as "RBIL") in the 1990s. The publication is currently at revision 61 as of 17 July 2000 with almost 8 MB of ASCII text including close to 9600 entries plus about 5400 tables, fully cross linked, which would result in more than 3700 pages (at 60 lines per page) of condensed information when printed. Of this, the interrupt list itself makes up some 5.5 MB for more than 2500 pages printed. While the project is not officially abandoned and the website is still maintained (as of 2025), new releases have not been forthcoming for a very long time, despite the fact that information was still pending for release even before the INTER61 release in 2000. New releases were planned for at several times in 2001 and 2002, but when they did not materialize, portions of the new information on DOS and PC internals provided by Paul were circulated in preliminary form in the development community for peer-review and to assist in operating system development.

See also BIOS interrupt call DOS API INT (x86 instruction) Malware analysis

Notes

References

External links Official website Delorie, DJ, ed. (2000-07-17). "Ralf Brown's Interrupt List". 61. Archived from the original on 2017-08-22. Retrieved 2017-08-22. (NB. Delorie Software's HTML-converted version of INTER61.) Perkel, Marc, ed. (2000-07-17). "Ralf Brown's Interrupt List: Indexed HTML Version - Release 61: A Gift to DOS Programmers". 61. Archived from the original on 2017-08-24. Retrieved 2017-08-24. (NB. Computer Tyme's HTML-converted version of INTER61.)

Worked examples

Example 1 — a first encounter with Ralf Brown's Interrupt List

Start with the simplest possible case. Write down what Ralf Brown's Interrupt List claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ralf Brown's Interrupt List before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ralf Brown's Interrupt List ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ralf Brown's Interrupt List

In research: Ralf Brown's Interrupt List appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ralf Brown's Interrupt List in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ralf Brown's Interrupt List is common in secondary-school and first-year university syllabi. It links to neighbouring topics History of computing, IBM PC compatibles, Interrupts, so understanding it makes those chapters shorter.
In everyday life: Look for Ralf Brown's Interrupt List outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Ralf Brown's Interrupt List in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ralf Brown's Interrupt List means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ralf Brown's Interrupt List out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ralf Brown's Interrupt List in simple terms?

Why does Ralf Brown's Interrupt List matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ralf Brown's Interrupt List?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ralf Brown's Interrupt List.