Epson MX-70 An Introduction to Dot Matrix Printing, (Subtitled, “Does a Dull Title Make a Topic Dull?“), How Dot Martrix Printing Works

An Introduction to Dot Matrix Printing

Chapter 4

An Introduction to Dot Matrix Printing

(Subtitled, “Does a Dull Title Make a Topic Dull?“)

My Computer Can’t Do High Resolution Graphics!

Correction, your computer can do high resolution graphics - on the MX-70 printer. Any computer that has the BASIC CHR$ function and the correct computer/printer interface can punch out super graphics on the MX-70. It’s as easy as sending CHR$ (0), . . . through CHR$ (255).

Unfortunately, that may not be as simple as it sounds. If you are fluent in Binary math, you know it takes 8 bits to count from 0 to 255 to specify the above 256 codes. (2 to the 8th power is 256.) (If you aren’t fluent in Binary math, it still does. Hang in there.)

Many computers and printer interfaces only support 7 bits of code data, hence, transmit to the printer only the ASCII code numbers between O-127. At this writing, Epson’s Apple parallel interface card is in this category since Apple BASIC does not control the eighth bit. It is quite possible to drive the MX-70 nicely with only code numbers from 0 to 127, but certain things are more difficult.

How Dot Martrix Printing Works

To really understand dot matrix printing, we have to understand how the print head works. It contains 9 “wires” or “pins” positioned one above the other, as

seen in Figure 4-l.

Dot matrix

Figure 4-1

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