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发表于 2008-11-22 23:30:24
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Life Without Hard Disk Drives2 f0 M: Q6 m( y- I7 w$ b
# G: |3 d' z7 g7 eIt's very hard for modern computer users to even consider what "computer life" would be like without hard disk drives. After all, most of us now have billions and billions of bytes of information ready at our fingertips (apologies to Carl Sagan... ;^) ). What was using a computer like before we had hard disk drives? In a word... inconvenient.! O. Q0 l% [8 j2 w3 f. s
Some of the very earliest computers had no storage at all. Each time you wanted to run a program you would have to enter the program manually. Needless to say, this was a major pain in the butt. Even more than that, it made most of what we consider today to be computing impossible, since there was no easy to way to have a computer work with the same data over and over again. It was quickly realized that some sort of permanent storage was necessary if computers were to become truly useful tools.6 U& T t5 X# \1 M* c/ i! N* A1 A
The first storage medium used on computers was actually paper. Programs and data were recorded using holes punched into paper tape or punch cards. A special reader used a beam of light to scan the cards or tape; where a hole was found it read a "1", and where the paper blocked the sensor, a "0" (or vice-versa). This was a pretty simple arrangement. I remember using a punch station, which was like a workstation where you typed characters and the machine punched the holes into the cards. While a great improvement over nothing, these cards were still very inconvenient to use. You basically had to write the entire program from scratch on paper, and get it working in your mind before you started trying to put it onto cards, because if you made a mistake you had to re-punch many of the cards. It was very hard to visualize what you were working with. The card readers had a tendency to jam (the old one at my high school was nicknamed the "IBM 1443 card chewer".) And heaven help you if you dropped a stack of cards on the floor...  Still however, paper was used as the primary storage medium for many years. X' a5 _& w$ y
The next big advance over paper was the creation of magnetic tape. Almost everyone has at least seen pictures of the large reels of tape used in older computers. Recording information in a similar to way to how audio is recorded on a tape, these magnetic tapes were much more flexible, durable and faster than paper tape or punch cards. Of course, tape is still used today on modern computers, but as a form of offline or secondary storage. Before hard disks, they were the primary storage for some computers. Their primary disadvantage is that they must be read linearly; it can take minutes to move from one end of the tape to the other, making random access impractical.
( b( u# R) C r* p2 \: ? Warning: Nostalgia mode activated. Be very afraid. . h8 q" F, {! M9 [( B* ]+ {( c* }8 T
Personal computers developed much later than the early, large mainframes, and were therefore the beneficiaries of advancements in storage technologies fairly early on in their existence. My first computer was purchased for me by my parents in 1980: an Apple ][. A great little machine for learning on, using it gave me a profound appreciation for the importance of storage: because it had none! No hard disk drive, not even a floppy disk drive. My choices were to type in programs by hand (which I did sometimes) or try to load them from a cassette tape. Yes, an audio cassette tape. If you thought modern computer tape drives were unreliable, you should have tried getting that to work! (Oh, and I also had to walk barefoot through three feet of snow to get to school... uphill both ways!)
' t$ g. M# W( ?8 L0 I/ M% uI later purchased a low-density, single-sided floppy disk drive for my Apple. Boy, what a feeling of freedom that was! I could load and save programs and data easily, something I could never do before. That disk drive cost C$700 (back when the Canadian dollar was worth not much less than the U.S. dollar.) The biggest advantages of floppy disks over tapes are the ability to randomly access the data, and much better portability. They don't have nearly as much capacity however.) \1 N* H4 B3 f, E
The first IBM PCs also had no hard disk drive, but rather employed one or two floppy disk drives. While of course far better than nothing, floppy disk drives were slow, small in capacity and relatively unreliable compared to even the earliest hard disks.* \+ H+ x. A" @' U
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[ 本帖最后由 easylife 于 2008-11-22 23:34 编辑 ] |
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楼主: easylife
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发表于 2008-11-22 09:25:20