Epson FX-80 User Manual page 79

The way Double-Strike gets this result is rather clever: each line is
printed once, then the paper is shifted up slightly (about 11216 of an
inch) and the entire line is printed again. In other words, each row has
a "shadow" (see Figure 4-1). Double-Strike printing fills in some of the
more obvious gaps in the dot matrix of the characters. The end result
is better looking print.
Figure 4·1. Single· and Double·Strike M.
The differences between Double- and Single-Strike printing don't
stop with the quality of print. Since each line is printed twice, the
throughput of the Double-Strike Mode is half that of normal. It's the
old trade-off between speed and print quality. With a normal print
speed of 160 characters per second (cps), the FX-80 still steps along
pretty lively in the Double-Strike, Mode.
Programming note: Notice that the printer always expects another
code after the ESCape. This second code tells the
printer which mode to tum on or off. In the case
of Double-Strike Mode, we use the quoted letter
G ("G") to tum it on and UH" to tum it off. The
letters, however, don't have to stand alone inside
the quotes. Consider:
48
1~
LPRINT CHR$(27)"GDOUBLE-STRIKE PRINT IS DARKER";
2~ LPRINT CHR$(27)"H THAN SINGLE-STRIKE"