January 1, 2013

The Laws of Computing and Software Development




The Laws of
Computing and Software Development



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.

Anderson's Law (Law of Computability)
Any system or program, however complicated, if looked at in exactly the right way, will become even more complicated.

For every scientific (or engineering) action, there is an equal and opposite social reaction.

Adding manpower to a late software project makes it later.

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.

The only way of discovering the limits of the possible is to venture a little way past them into the impossible.

Any sufficiently advanced technology is indistinguishable from magic.

Any piece of software reflects the organizational structure that produced it.

If you don't know what your program is supposed to do, you'd better not start writing it.

The most ineffective workers are systematically moved to the place where they can do the least damage: management.

The user base for strong cryptography declines by half with every additional keystroke or mouse click required to make it work.

Ellison’s Law of Data
Once the business data have been centralized and integrated, the value of the database is greater than the sum of the preexisting parts.

As the rate of erroneous alerts increases, operator reliance, or belief, in subsequent warnings decreases.

The more highly adapted an organism becomes, the less adaptable it is to any new change.

The time to acquire a target is a function of the distance to and the size of the target.

There does not now, nor will there ever, exist a programming language in which it is the least bit hard to write bad programs.

If you put tomfoolery into a computer, nothing comes out but tomfoolery. But this tomfoolery, having passed through a very expensive machine, is somehow ennobled, and no one dares to criticize it.

Bandwidth grows at least three times faster than computer power.

As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one.

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.

The time to make a decision is a function of the possible choices he or she has.

The time to make a decision is a function of the possible choices he or she has.

Inside every large problem is a small problem struggling to get out.


A task always takes longer than you expect, even when you take into account Hofstadter’s Law.

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.

smart(employees) = log(employees), or “No matter who you are, most of the smartest people work for someone else.”

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.

Eric S. Raymond
Given enough eyeballs, all bugs are shallow.

People under time pressure don’t think faster.

Lubarsky's Law
There's always one more bug.

In network theory, the value of a system grows as approximately the square of the number of users of the system.

Yes, you can; but what is the goal?

M. McCafferty
Do Good Now, make it better later.
(Sell the software you have, including the bugs; improve with the profits.)

The number of transistors on an integrated circuit will double in about 18 months.

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.

Software is a gas; it expands to fill its container.

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

The explanation requiring the fewest assumptions is most likely to be correct.

Osborn’s Law
Don Osborn
Variables won’t; constants aren’t.

Be conservative in what you send, liberal in what you accept.

Suggested by Joseph Juran, named after Vilifredo Pareto
For many phenomena, 80% of consequences stem from 20% of the causes.
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.

In a hierarchy, every employee tends to rise to his level of incompetence.

The utility of large networks, particularly social networks, scales exponentially with the size of the network.

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.

The time it takes your favorite application to complete a given task doubles with each new revision.

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.

Ninety percent of everything is crud.

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.

Software gets slower faster than hardware gets faster.

Every program attempts to expand until it can read mail. Those programs that cannot so expand are replaced by ones that can.