Classic Computer Magazine Archive COMPUTE! ISSUE 61 / JUNE 1985 / PAGE 10


The Editors and Readers of COMPUTE!

If you have any questions, comments, or suggestions you would like to see addressed in this column, write to "Readers' Feedback," COMPUTE!, P.O. Box 5406, Greensboro, NC 27403. Due to the volume of mail we receive, we regret that we cannot provide personal answers to technical questions.

Closing The Quality Gap

I thought letter quality was a term used to describe typewriters or daisywheel printers. Now I have seen many dot-matrix printers claiming to be letter quality. How is this possible?

Alex Cutrone

Perhaps you're reading too much into the term letter quality. It simply means "good enough to use in a business letter." Printing of this quality has traditionally been equated with daisywheel printers, which create crisp, solid images by striking an inked ribbon with little character-shaped hammers, just like a typewriter.

Dot-matrix printers use a different technique, forming each character out of many tiny dots. The printhead contains several small pins which can be individually fired, pressing the ribbon against the paper to make a dot. As the printhead moves across the paper, the pins are rapidly fired in various combinations to form different characters.

Early dot-matrix printers left noticeable gaps between the character dots, giving the print a grainy appearance. As dot-matrix technology has improved, these gaps have been all but eliminated, producing print of much higher quality.

One way to improve print quality is to double-strike each character. Printing a character twice in the same spot puts more ink in each dot; since the dots are darker (and a little fatter), the print looks better. Enhanced printing also double-strikes each character, but offsets the printhead very slightly (less than a dot's width) before printing the character a second time. This fills in much of the space between dots.

Most dot-matrix printers have pins that are round in cross section. Since round dots don't fit neatly together, dot-matrix characters tend to have wavy edges, even in enhanced printing modes. To give the characters crisper edges and further alleviate the gap problem, some manufacturers have switched to pins with a squarer cross section. However, you can obtain high quality print from a machine that uses round pins: The Apple Imagewriter is one example.

By looking closely, you can still distinguish the best dot-matrix print from so-called letter-quality print. A letter produced with a Macintosh and an Apple Imagewriter doesn't look exactly the same as one typed on an IBM Selectric. But that's not to say it doesn't look good enough for "serious" use. Some people would say that the Macintosh-generated letter looks more impressive than one done on a Selectric.

The fact is that many people are already using dot-matrix printers for business correspondence. Judged by that practical standard, the better dot-matrix printers are indeed letter-quality machines. If you're thinking of purchasing a printer, see "How to Buy the Right Printer" elsewhere in this issue.