This is where the numbers down the left side of the grid come in. Notice that there is a
number for each row of dots and that each number istwice the number below it. By making
these numbers powers of two we can take any combination of dots in a vertical column and
assign them a unique value.
Assigning a value of character space
Besides being able to specify the actual width of the character, this printer allows you to
specify the position in the standard grid where the character will print. You must specify
the dot column in which the printed character starts and the dot column in which the
character ends. Why, you may ask, would you want to define a character this way instead
of merely defining the overall width of the character? Because this printer’s proportional
character definitions can also be used to print normal width characters, and by centering
even the narrow characters in the complete grid they will look good even you are not
printing them proportional.
The three bytes are used to specify the width of the character and the space to be allowed
on either side of it. The left space (in dot columns) is specified by rnOand the right space
is specified by
m2. The second byte (ml) specifies the width of the character in dots. By
varying the width of the character itself and the spaces around it, you can actually create
proportional width characters.
When defining characters, the number of printed columns
(ml), and the sum of side spaces
and the character width
(mO+ml +m2) cannot exceed the value shown below.
Character mode
ml mO+ml +m2
Pica characters
31 36
Elite characters
27 30
Semi-condensed 19 24
Proportional
37
42
Super/subscript
19
36
Proportional super/subscript
37
42
Sample program
To demonstrate how to use the 24-dot download characters, let’s use the “telephone”
character and the other user-defined characters to print a small graph. This program will do
just that:
1000 WIDTH “LPT1 : “ , 255
1010 LPRINT CHR$ (27 );“Xl
“ ;
1020 LPRINT CHR$( 27) ;“it”;CHR$( O) :
1030 LPRINT CHR$( 60) ;CHR$( 61 );
1 FOR N=60 TO 61
1050 READ LS :LPRINT CHR$ (Ls) ;
1060 READ CW :LPRINT CHR$ (CW) :
1070 READ RS :LPRINT CHR$ (Rs );
1080 FOR M=1 TO CW’k3
1090 READ MM
1100 LPRINT CHR$(MM) ;
1110 NEXT M
1120 NEXT N
Chapter7 DOWNLOAD CHARACTERS 69
