Now that you've read all about why you need a spec and what a spec has in it, let's talk about who should write them.
Who writes specs?
Let me give you a little Microsoft history here. When Microsoft started growing seriously in the 1980s, everybody there had read The Mythical Man-Month, one of the classics of software management. (If you haven't read it, I highly recommend it.) The main point of that book was that when you add more programmers to a late project, it gets even later. That's because when you have n programmers on a team, the number of communication paths is n(n-1)/2, which grows at O(n2).
So the programmers at Microsoft were worried about how to write bigger and bigger programs, when the prevailing wisdom of the day was that adding programmers just makes things worse.
Charles Simonyi, Microsoft's long time "chief architect", suggested the concept of master programmers. The idea was basically that one master programmer would be responsible for writing all the code, but he or she would rely on a team of junior programmers as "code slaves". Instead of worrying about debugging every function, the master programmer would basically just prototype each function, creating the bare outline, and then throw it to one of the junior programmers to implement. (Of course, Simonyi would be the Master Master Programmer.) The term "Master Programmer" was a bit too medieval, so Microsoft went with "Program Manager."
Theoretically, this was supposed to solve the Mythical Man-Month problem, because nobody has to talk to anyone else -- every junior programmer only talks to the one program manager, and so communication grows at O(n) instead of O(n2).
Well, Simonyi may know Hungarian Notation, but he doesn't know Peopleware. Nobody wants to be a code slave. The system didn't work at all. Eventually, Microsoft discovered that despite the alleged Mythical Man Month, you can still add smart people to a team and get increased output, although at decreasing marginal values. The Excel team had 50 programmers when I was there, and it was marginally more productive than a team of 25 would have been -- but not twice as productive.
The idea of master/slave programming was discredited, but Microsoft still had these people called program managers bouncing around. A smart man named Jabe Blumenthal basically reinvented the position of program manager. Henceforth, the program manager would own the design and the spec for products.
Since then, program managers at Microsoft gather requirements, figure out what the code is supposed to do, and write the specs.
Author: Joel Spolsky
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