I've done a lot with the classic IBM 1403 line printer. The basic idea is that a rotating chain has the characters on it and zips around at 90.3 inches per seco

I've done a lot with the classic IBM 1403 line printer. The basic idea is that a rotating chain has the characters on it and zips around at 90.3 inches per second. The printer has 132 hammers, one for each column on the page. When the right character lines up with a hammer, the hammer fires, printing the character. This lets the printer output a full line in 80 milliseconds. The details of the print chain process are much more complex than you'd expect (so feel free to skip this paragraph). The computer has to constantly check to see when a hammer should fire. One important thing is that only one hammer lines up with a character at a time. (It's physically impossible to fire all the hammers at once.) During this time, the computer reads the corresponding character from memory and fires the hammer if it matches. To make this work, the chain/hammer timing has to match the core memory cycle timing. The chain spacing is very slightly different from the hammer spacing, so you end up with a vernier effect where the aligned character position changes much faster than the chain actually moves. I made an animation that might make things clearer: http://righto.com/ibm1401/printchain.html http://righto.com/ibm1401/printchain.html Another thing that makes the printer fast is it has a hydraulic motor to advance the paper very quickly. Inconveniently, the printer at the Computer History Museum is leaking hydraulic fluid, so we need to mop it up regularly. (That's one advantage of your home printer.) The print quality of the 1403 line printer was much better than competitors because it used a chain instead of typebars or a drum. In particular, if the timing was a bit off, the chain caused the character to be shifted left or right. Other approaches caused the character to be shifted up or down. A left-right shift is barely noticeable, while an up-down shift makes the text look wavy and awful. By the way, a laser printer (e.g. Brother) is a good choice for a home printer if you want more speed and don't like the expense of ink.