Commodore PC 20 User Manual page 368

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MS-DOS User's Reference
(O)utput
Using the Output
command
Output
Purpose:
Sends the specified
byte
to the output port specified by
value.
Syntax:
Ovalue byte
Comment:
A 16-bit port address is allowed.
Example:
Suppose you want to debug to output the byte value 4F to
output port 2F8. To do this you could simply type the following
command:
02FB 4F
c