Commodore PET User Manual page 183

Three-Key Rollover (Small Keyboard)
Three-key rollover remembers the second and third keystrokes when three
keys are pressed before the first key is released. Three-key rollover is unpredic-
table on the PET and should not be depended upon, as correct printing depends
upon the keyboard position of ail three keys. This section is only for those
readers who are interested in PET trivia and who want to experiment in
three-key rollover.
The compact keyboard may be divided into odd and even rows. as shown in
Figure 5-1.
Figure 5-1. Odd/Even Division of PET Keyboard
If the three keystrokes. KeY1. KeY2. and KeY3. are not adjacent to each other.
then the result is correct and will be printed as:
(characters of) KeY1 KeY2 KeY3
But if the three keystrokes are adjacent. the resu It is incorrect. and the type
of error depends upon whether KeY1 is in an odd or even column. Figure 5-2 il-
lustrates the two different types of errors that occur depending on the position of
KeY1'
To demonstrate this phenomenon. let us use three actual examples from the
keyboard.
The first example shows three non-adjacent keystrokes simultaneously en-
tered. The diagram shows F. U. N entering the buffer and then printing to the
screen in the correct order.
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