A REALLY Big Deck of Cards
Every once in a while, while I'm contemplating just how old I am, I stop to be thankful for even how much older I'm not. There are many people alive today who have programmed computers with patch cords and toggle switches. I met a gentleman at a party this past summer who was in radiological health physics at the Manhattan Project. (You can bet they didn't use the name of his department in the open press!) Back in those days, "computers" were humans, people who did computations. My introduction to computing was on a machine that used IBM punch cards, and the machine was served by a priesthood and various levels of acolytes*.
My first computer used a magnetic card reader. But the magnetic card was not the first computer storage medium I used. While I am not old enough to have participated in the patch cord days, I do remember the stacks of cards, and accessible-to-students card punch machines. And, although I'm comfortable with the statute of limitations having long passed, this is not the place to describe some of the things that "a friend" might have done with those machines. In any event, they were not mine; my first personal computer was an HP 9810. I bought it in 1969, I still have it, and although I'm not sure I could even find it in the company warehouse, I'd be willing to bet that if I could, its LED "registers" would initialize and display the stack contents. Gold plated printed circuit boards and connectors are great for longevity. This is the same computer I mentioned yesterday, the one that had 500 bytes of memory when I bought it, and which I was able to upgrade to 1K a year or so later. Although the magnetic cards were compact, longer ones were needed for upgraded machines with more memory.
From Magnetic Card To Hard Drive
The history of magnetic storage, which is essentially the history of "permanent storage" until the very recent past, is one of increasing storage density. Every square unit of magnetic material orients to the occasion by the application of magnetic fields. As the dimensions of the magnetized area needed to store a bit decrease, the amount of storage per unit area goes up by the square of the saving. The mechanical precision needed to achieve this increases, too, although presumably linearly. The magnetic card, used in my first computer's generation, gave way to little tape cartridges in the subsequent series, the 9825-45. Why not use floppy disks? They didn't exist! They only became available as accessories after the machines came out. And were they ever expensive! $5K for a few-hundred-kilobyte floppy drive, and $80 for a ten-pack of floppies. I dutifully bought them, however, because they were orders of magnitude faster and more reliable than the cartridges.
Finally, in the late 70's one could get hard drives for these little machines...
And so forth. Milestones escape me now, and I've programmed myself to use the term "sweet spot." At any epoch, there is an optimum hard-drive size that gives you the most gigabytes for your punybucks. Around the turn of the century it was about 20GB. A few years ago it was 80GB. Today, it's about 250GB. Anyone care to speculate as to when it will be difficult to buy a computer with less than a terabyte? Two years? Four?
And Back to Cards Again
Although computers have managed to increase their demand for memory at pretty much the same rate that the price of memory has decreased, I'm not sure that's so true with disk storage. Unless you're keen on storing visual media on your PC, the fact is that your hard drive may be large enough to hold every song and every picture you will ever hear or see in your entire life, and certainly more than enough for your reading material. But I'm going to stop here, because futuristic speculation isn't the point of this blog. Suffice it to say that I'm beginning to rethink my demand for a cell phone with an MP3 player that has a hard drive. Even tiny memory cards are invading the Gigabyte range, and when they get to fifty or so gigabytes, that may be "almost enough."
Not Those Cards, The Other Cards!
But the cards we started out with were the "IBM Punch Cards." You know me and my numbers, so if we can calculate whether memory cards float on water, we can certainly see how thick a stack of punch cards would have to be to equal your disk drive's storage capacity. Answer: Each card had 80 columns with 12 holes each. Disregarding their format, that's 120 bytes per card. At 143 cards to the inch, a deck of cards would have to be about as tall as you are to store a megabyte. A gigabyte, therefore, would require another 999 people standing on your shoulders, and the top person would be about a mile high. Another two thousand people and we're up to three gigabytes, but at that level you begin to need supplementary oxygen. By the time you've reached 8GB your stack of people is a navigation danger to jet airliners, and if you've got a 250G hard drive, look out for the space shuttle!
I won't try to calculate whether enough cards to fill a modern PC hard drive were even manufactured during their heyday, but given how many I saw in the trash and in ad-hoc confetti, it wouldn't surprise me at all.
*It turns out that there are, indeed, "various levels" of acolytes. But they're called "the minor orders," of which the acolyte is the highest, and the exorcist, lector, and ostiary are progressively lower. That will teach me to look things up, mid-blog. It also explains why there is nothing improbable about the need for the occasional exorcist in the computer room.