The term "pen number" is used in two different ways. The appropriate range is explained in the text describing the statement.
The first way in which the term "pen number" is used is for CRT color attribute values. The legal values are:
Pen
Color
136
White
137
Red
138
Yellow
139
Green
140
Cyan
141
Blue
142
Magenta
143
Black
The second way in which the term "pen number" is used is in statements affecting graphic colors. In these instances, pen numbers begin at zero and go to N-1, where N is the number of colors displayable at the same time on the computer display.
