Commodore VIC-20 - Page 297

Chapter 8: Peripheral Devices 283
Start / stop bits Some computers require that a certain number of null
bits be transmitted after each byte. These null bits are called stop
bits.
If the system uses these, the most common number is one
stop bit and one start bit.
If this is the case, the total number of
bits per byte increases to ten. This will slow the effective transmis-
sion rate slightly,
but will not impair the operation ofthe VIC 20
or the modem.
Line feed At the end of a line of data, the computer will typically send a
carriage return. Some systems also require a line feed after each
line
or data file.
ASCII This is the standard coding used to communicate the numbers 1
through 9 and upper- and lower-case letters. There are also a
number
of standard symbols and special characters used in the
ASCII (American Standard Code for Information Interchange)
system. The VIC
20 uses an extension of the ASCII character set
for its extended character set, but should use this extended set
only when communicating with other Commodore computers.
THE 1515 GRAPHIC PRINTER
The VIC 1515 Graphic Printer has a built-in character set that closely
resembles the character set
ofthe VIC 20. It includes upper- and lower-case
letters, numbers,
and graphic symbols. You can use the 1515 printer to print
fully programmable custom graphics of almost any size.
OPEN Statement
In order to access the VIC 1515 printer you must open a file to it. The
OPEN statement for the printer has the following format:
OPEN/n, dn, sa
where:
In The file number is the number you choose to access the file. You may choose
any number between 0 and
255
dn The device number for the printer may be either 4 or 5. This number may be
selected using a switch at the rear of the printer
sa
In most cases, you will not use a secondary address when you access the print-
er. The one exceptioll
to this is covered in the section on the ISIS printer's
character sets.