Computer Literacy: Part 1 is an essay by Jack Rusher, published here Wednesday, September 13, 2006. It is part of Science For Humanists.
A humanistic exploration of our digital helpers. See also parts two, three and four.
Introduction
You are reading this using a computer. Don’t try to deny it, we both know you are. Chances are that you do a great many things using your computer. In fact, we’ve reached a point in our cultural history where being able to use one is only slightly behind reading on the list of skills required to live an educated, first-world sort of life. This is what leads me to present you with this series of articles. They will, I hope, serve as a bridge by which any intelligent person with a general education can come to understand the inner workings of the devices they use every day.
The first parts will act as a basic primer, while the latter ones will give a highly metaphorical explanation of the discipline of computer science itself. The latter ones, if I’m successful, will entertain anyone with a playful and curious mind, but also provide those of you who have wound up working in programming or systems administration after a liberal arts background with a deeper understanding of the principles of computer science.
The Model of a Modern Postmaster General
Pierre, hard at work.
We’re going to describe the computer at which you are reading this article using a single long-lived analogy: the harried fait-tout postmaster, notary and general factotum serving a provincial French village shortly before the First World War. Your computer’s name is now Pierre.
Pierre does most of his work at a small desk near the window of his office, which is on the second floor of the town’s tiny train station. A few meters behind him rests a large cabinet full of index cards, on top of which are a set of instruction manuals, also arranged on index cards, for the various tasks that he performs in the course of his work.
When Pierre begins a new piece of work he collects the relevant cards from the cabinet, places them on his desk, and goes through them one at a time, squinting at them through his spectacles.
One of Pierre’s index cards.
1. The filing cabinet is the disk drive in your computer, its cards the data stored there. The desk is your computer’s memory. Pierre’s mind is the Central Processing Unit (CPU), which proceeds through the instruction manuals (the programs) provided by the regional bureaucracy (the programmers). His hands are what are called the “CPU registers,” which is a fancy way of saying “the part of the computer that holds things where the CPU can see them.”
Pierre is a diligent and hard-working civil servant, but he is also a bit dim, and has a kind of autistic literalness that drives him to carry out every directive in exactly the way it’s specified. He is, as the old joke goes, the kind of person who would never escape the shower after reading the words “lather, rinse, repeat” on a shampoo bottle. He is also so arthritic that it takes him a very long time to walk to the filing cabinet1.
2. It should be noted that Pierre, given his simplicity, represents a computer on the order of, say, a Commodore 64. If we were to extend the metaphor to a modern machine we would have a Hindu deity with many sets of arms to hold many, many cards, several heads to represent multiple CPUs, and so on.
3. At the writing of this article it takes about six milliseconds (six one-thousandths of a second) to fetch something from a computer’s disk drive, but only seventy nanoseconds (seven one-hundred-millionths of a second) to load something from memory into the CPU. This difference is roughly similar in magnitude to that between taking a single step and walking fifty miles.
The technocrats at the regional office are well aware of Pierre’s idiosyncrasies2, which are shared by all the other postmasters general in France. They take pains to specify his instructions in minute and clear detail, always trying to define his tasks in such a way that Pierre will be able to complete them with the fewest trips to the filing cabinet given the limited number of cards he can fit on his desk at any given moment3.
If the process of explaining, in pedantic detail, the minute steps of what should be a simple process to someone of Pierre’s personality sounds like tedious work, you’ve understood software engineering perfectly.
In the next part of this series we will look inside the Technocrats’ Guild, discuss some of the problems they’ve faced, and take apart a few common solutions to those problems.