Even better some of the early printers (e.g. IBM 1132) had a wheel for every character position, all on a common axle, so you told the printer which character y

Even better some of the early printers (e.g. IBM 1132) had a wheel for every character position, all on a common axle, so you told the printer which character you wanted, then set bit fields in memory for which positions to strike, then wait for interrupt and repeat until you have printed all the characters that were used on that line, then told it to advance. The timing for this was finicky, to the point that the cheap 1130 wasn't capable of doing this fast enough, which was solved by IBM by making it run at a higher clock speed when at interrupt level 1. As you might imagine many of those machines spent a lot of time at interrupt level 1 doing things unrelated to printing