Graphics

The print head

To urtderstand dot graphics you need to know a little ‘about ‘how

your printer's print head works.

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As the print head moves across the page, electrical impulses cause the pins to fire. Each ‘time a pm fires, it strikes the inked ribbon and presses it against the paper to produce a small dot. As the head moves across the page, the pins fire time after time in different patterns to produce letters, number& or symbols.

Dot patterns

The DFX’s print head is able to print graphics as well as text because graphic images are formed on the printer about the same way that pictures in newspapers and magazines are printed. If you

look closely at a newspaper photograph, you can see that it is made up of many small dots, Your PIT&@; also .forms its images with

patterns of dots, as many as 240 dot positions per inch horizontally and 72 dots vertically. The images printed by the printer can, therefore, be as finely detailed as the one on page 4-10.

In its’main @aphics”mode, ydur’prir& ‘tiiints one co&&‘-of dots for each code it receives, and it uses only the top eight of the nine pins. Therefore,. your ,graphics program muat send codes for dot patterns, one numb for ~each.,colurnn in a line. .l$o.r each o&hose columns, the print .head printa-the.pattern of dots -you have specified.

To print figures taller than eight dots, the print head makes more than one pass, The printer prints one line, then advances the paper and prints another, just, as it does with text.

To keep the print head from leaving gaps‘between the graphics lines as it does between the text lines, tho,line spacing must be changed to eliminate the space&etween <lined ,With a cw in line spacing, your printer can print finely detailed graphic images that give no indication that they are made of separate lines, ‘each no more than 8/72nds of an inch tall.

Software and Graphics 4-11