Laws of Software Development

Moses wielding a cell phone

[This was also cross-posted to the Tucows Developer Blog]

Inspired by Phil Haack’s article 19 Eponymous Laws of Software Development, I decided to collect laws, axioms and rules pertaining to mainstream software development and put them in a nice, easy-to-read table.

This is by no means a complete list of laws; I’ve purposely stuck to the ones that apply to everyday software development and steered clear of the more theoretical ones. Maybe I’ll compile a more complete list someday.

You’ll notice that some of the laws come from the world of biology — they also appear in some lists of software laws, and I think they still apply.

The Law Who Said It What it Says
Amdahl’s Law Gene Amdahl The speedup gained from running a program on a parallel computer is greatly limited by the fraction of that program that can’t be parallelized.
Augustine’s Second Law of Socioscience Norman Augustine For every scientific (or engineering) action, there is an equal and opposite social reaction.
Brooks’ Law Fred Brooks Adding manpower to a late software project makes it later.
Clarke’s First Law Arthur C. Clarke When a distinguished but elderly scientist states that something is possible he is almost certainly right. When he states that something is impossible, he is very probably wrong.
Clarke’s Second Law Arthur C. Clarke The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
Clarke’s Third Law Arthur C. Clarke Any sufficiently advanced technology is indistinguishable from magic.
Conway’s Law Melvin Conway Any piece of software reflects the organizational structure that produced it.
Cope’s Rule Edward Drinker Cope There is a general tendency toward size increase in evolution.
Dilbert Principle Scott Adams The most ineffective workers are systematically moved to the place where they can do the least damage: management.
Ellison’s Law of Cryptography and Usability Carl Ellison The userbase for strong cryptography declines by half with every additional keystroke or mouseclick required to make it work.
Ellison’s Law of Data Larry Ellison Once the business data have been centralized and integrated, the value of the database is greater than the sum of the preexisting parts.
The Law of False Alerts George Spafford As the rate of erroneous alerts increases, operator reliance, or belief, in subsequent warnings decreases.
Fisher’s Fundamental Theorem R. A. Fisher The more highly adapted an organism becomes, the less adaptable it is to any new change.
Fitts’ Law Paul Fitts The time to acquire a target is a function of the distance to and the size of the target.
Flon’s Axiom Lawrence Flon There does not now, nor will there ever, exist a programming language in which it is the least bit hard to write bad programs.
Gilder’s Law George Gilder Bandwidth grows at least three times faster than computer power.
Godwin’s Law Mike Godwin As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one.
Grosch’s Law Herb Grosch The cost of computing systems increases as the square root of the computational power of the systems.
Hartree’s Law Douglas Hartree Whatever the state of a project, the time a project-leader will estimate for completion is constant.
Heisenbug Uncertainty Principle Jim Gray Most production software bugs are soft: they go away when you look at them.
Hick’s Law William Edmund Hick The time to make a decision is a function of the possible choices he or she has.
Hoare’s Law of Large Programs C. A. R. Hoare Inside every large problem is a small problem struggling to get out.
Hofstadter’s Law Douglas Hofstadter A task always takes longer than you expect, even when you take into account Hofstadter’s Law.
Jakob’s Law of the Internet User Experience Jakob Nielsen Users spend most of their time on other sites. This means that users prefer your site to work the same way as all the other sites they already know.
Joy’s Law Bill Joy smart(employees) = log(employees), or “No matter who you are, most of the smartest people work for someone else.”
Kerckhoffs’ Principle Auguste Kerckhoffs In cryptography, a system should be secure even if everything about the system, except for a small piece of information — the key — is public knowledge.
Linus’ Law Eric S. Raymond, who named it after Linus Torvalds Given enough eyeballs, all bugs are shallow.
Lister’s Law Timothy Lister People under time pressure don’t think faster.
Metcalfe’s Law Robert Metcalfe In network theory, the value of a system grows as approximately the square of the number of users of the system.
Moore’s Law Gordon Moore The number of transistors on an integrated circuit will double in about 18 months.
Murphy’s Law Captain Edward A. Murphy If there are two or more ways to do something, and one of those ways can result in a catastrophe, then someone will do it.
Nathan’s First Law Nathan Myhrvold Software is a gas; it expands to fill its container.
Ninety-ninety Law Tom Cargill The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time.
Occam’s Razor William of Occam The explanation requiring the fewest assumptions is most likely to be correct.
Osborn’s Law Don Osborn Variables won’t; constants aren’t.
Postel’s Law (the second clause of the Robustness Principle) Jon Postel Be conservative in what you send, liberal in what you accept.
Pareto Principle (a.k.a. “The 80-20 Rule”) Suggested by Joseph Juran, named after Vilifredo Pareto For many phenomena, 80% of consequences stem from 20% of the causes.
Parkinson’s Law C. Northcote Parkinson Work expands so as to fill the time available for its completion.
Pesticide Paradox Bruce Beizer Every method you use to prevent or find bugs leaves a residue of subtler bugs against which those methods are ineffectual.
The Peter Principle Laurence J. Peter In a hierarchy, every employee tends to rise to his level of incompetence.
Reed’s Law David P. Reed The utility of large networks, particularly social networks, scales exponentially with the size of the network.
Rock’s Law Arthur Rock The cost of a semiconductor chip fabrication plant doubles every four years.
Sixty-sixty Rule Robert Glass Sixty percent of software’s dollar is spent on maintenance, and sixty percent of that maintenance is enhancement.
Spector’s Law Lincoln Spector The time it takes your favorite application to complete a given task doubles with each new revision.
Spafford’s Adoption Rule George Spafford For just about any technology, be it an operating system, application or network, when a sufficient level of adoption is reached, that technology then becomes a threat vector.
Sturgeon’s Revelation Theodore Sturgeon Ninety percent of everything is crud.
Tesler’s Law of Conservation as Complexity Larry Tesler You cannot reduce the complexity of a given task beyond a certain point. Once you’ve reached that point, you can only shift the burden around.
Weibull’s Power Law Waloddi Weibull The logarithm of failure rates increases linearly with the logarithm of age.
Wirth’s Law Niklaus Wirth Software gets slower faster than hardware gets faster.
Zawinski’s Law Jamie Zawinski Every program attempts to expand until it can read mail. Those programs which cannot so expand are replaced by ones which can.

121 replies on “Laws of Software Development”

I think this law is relevant:

Weinberg’s Law: If builders built buildings the way programmers wrote programs, then the first woodpecker that came along would destroy civilization. (Jerry Weinberg)


While we’re on the FFFB’s, don’t forget:

Dope will get you through times of no money better than money will get you through times of no dope.

In addition to having a cool name, Melvin Kranzberg was one of the founding figures of the history of technolgy. His laws apply to most any kind of technology, wired or otherwise.
Kranzberg’s Laws
1st: Technology is neither good nor bad; nor is it neutral.
2nd: Invention is the mother of necessity.
3rd: Technology comes in packages, big and small.
4th: Although technology might be a prime element in many public issues, nontechnical factors take precedent in techology-policy decisions.
5th: All history is relevant, but the history of technology is most relevant
6th: Technology is a very human activity, and so is the history of technology.

Europium’s First Law of Indoor Plumbing

The sooner you have to pee, the more distant the restroom.

Europium’s Second Law of Indoor Plumbing

If you can’t hold it any longer, the restroom will be located on the fourth floor, is locked, and requires a key held by the cashier who is presently using the other restroom in the basement.

Putt’s Law: Technology is dominated by two types of people: those who understand what they do not manage, and those who manage what they do not understand.

All Trivial Cases are Non-trivial:
“In the Universe, whatever is not specifically forbidden in physics will eventually occur.”

Great set. One of my favorite laws of programming is what I call “Strathmann’s Law” or sometimes “Strathmann’s Law of Project Management”:
to whit:
“Nothing is so easy as the job you imagine someone else doing.”

Poor William, blamed for a razor he didn’t invent and that nobody ever seems to get right, while his contribution to the idea of universal rights goes unnoticed.

I guess that’s what you get for being a heretic.

(I’ve always wondered how people ‘translate’ it, when he never wrote it down. It was probably Dun Scotus.)

Now this explains some of the vast number of managers I have had in the 70’s, 80’s and 90’s. Those fools always thought I had it easy when in fact my wife was complaining about how hard I worked.

So, my corollary to this truth of yours is that the person imagining doubtless has little or no empathy for the worker’s efforts.

Where did we get those people from? By the way Fred, think about some of the higher up managers at Smiths.

Miles Archer:

I’m pretty sure it’s attributable to a British comedian called Vic Reeves. Although I think he originally stated that “86.6% of all statistics are made up on the spot” which is both more accurate and funnier.

Orth’s First Law of Programming

“Never modify bad code, it just gets worse.”

Corollaries of Orth’s First Law of Programming

“Always start with a clean piece of paper.”
“There is no cure for bad code.”

Orth’s Second Law of Programming

“No matter how simple the task, it will consume more time than estimated if it must be repeated many, many times.”

And finally, I can’t take credit for this one because it predates me by decades if not centuries….

“There’s never time to do it right in the first place, but there’s always time to do it over when it doesn’t work.”

@ Andy B.

Yes! Thanks much. Oh, and BTW, here is the complete quote…

“A complex system that works is invariably found to have evolved from a simple system that worked.

A complex system designed from scratch never works and cannot be patched up to make it work.”

Atwood’s Law: “any application that can be written in JavaScript, will eventually be written in JavaScript”.

Hofstadter’s Law has one ‘ti’ too many…

“Whatever the state of a project, the time a project-leader will estimate for comple_ti_tion is constant.”

(And I’ll bet that’s not the only law he could put his name to.)

Rules of Estimations

– A job will always take twice the time you estimate.

– A customer will always want a job done in half the time you estimate.

– This remains true when you substitute ‘money’ for ‘time.’

– They remain in force, even if you double or halve your estimates in attempts to compensate for the effect of these rules.

(ie: Doubling your estimate results in quadrupling the end effect.)

My own personal law of copiers (I used to repair them for a living):

The itch on your nose is directly proportional to the amount of toner on your fingers.

Richards’ Laws of Data Security:
1. Don’t buy a computer.
2. If you must buy a computer, don’t turn it on.

To whom it may concern: I think Fred Strathmann is an old friend of mine – from grade school. I wonder if you have an e-mail address for him? For myself, I teach philosophy, psychology and mathematics at a few places in singapore so it is hard for me to track people down in the USA. Sincerely, Richard McD

Greenspun’s Tenth Rule seems appropriate here as well: “Every sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp.”

I prefer the abbreviated version: “Those who do not understand Lisp are doomed to reinvent it.”

Not specifically programming related, but for security in general (more and more relevant to programming everyday in the Web 2.0 world):

Spafford’s first principle of security administration – “If you have responsibility for security but have no authority to set rules or punish violators, your own role in the organization is to take the blame when something big goes wrong.”


Don’t know who said them:

“Never test for an error you don’t know how to handle.”

“Debuging code is twice as hard as writing it. If you write it to the best of your ability, then you will never be able to debug it.”

“In the chart, if a breezier paraphrasing the law exists, I used that instead. Hence, wherever possible, I linked the name of each law to a page that had a more technically correct description (including formulae, where applicable).”

The link part is good, but the paraphrase you used is simply incorrect. It’s very common for people to use this incorrect description of Occam’s Razor, but that does not make it more correct. Occam’s Razor does not say anything about an idea being correct or even likely to be correct, just that you probably want to go with it until the evidence favors something else.

[…] Laws Of Software Development Ferdy October 21st, 2007 – 11:07 pm Software Development Average time to read 0:20 minutes It’s a bit old, but I discovered these links today. Phil Haack collected together in a post 19 Eponymous Laws Of Software Development, and Joey deVilla, inspired by Phil’s article, collected more laws, axioms and rules pertaining to mainstream software development and put them in a nice, easy-to-read table in Laws of Software Development. […]

Richard McDonough:
Are you the person I once knew at Cornell’s grad school, back around 1970?

Europium’s Law of Inevitability: “The manager you work for will always be the one who believes that nine women can produce a baby in one month.”

Europium’s Corollary: “The manager you work for will inevitably be the one who pressured his neurosurgeon into performing the six-hour operation in three.”

[…] Global Nerdy » Blog Archive » Laws of Software Development Inspired by Phil Haack’s article 19 Eponymous Laws of Software Development, I decided to collect laws, axioms and rules pertaining to mainstream software development and put them in a nice, easy-to-read table. […]

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