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Now you translate the dot pattern you’ve created on paper to a numeric
format so you can send the information to your printer. Every dot has an
assigned value. Each vertical column (which has a maximum of
24
dots) is
first divided into three groups of eight dots. Each group of eight dots is
represented by one byte. Since one byte consists of eight bits, one bit
represents one dot.
Data numbers
The bits within each byte have values of
1, 2, 4, 8, 16, 32, 64,
and 128. In
the vertical column of dots, the bits are arranged so that the most significant
bit (which has a value of 128) is at the top and the least significant bit
(which has a value of 1) is at the bottom.
The next illustration shows you how to use this method to calculate the
data numbers for the example character. On the left side of the figure, the
data numbers are calculated for the middle column. The value of each byte
is calculated by adding the values of the rows where dots appear. The right
side of the figure shows the whole character with the three data numbers for
each column indicated at the bottom.
This manual uses decimal numbers because the example programs in this
manual are written in BASIC and everyone is familiar with decimals. The
data you send to your printer, however, can be in any form (binary,
decimal, hexadecimal) that you can use with your programming language.
4-26
Using Software and Graphics