User`s guide

How Your Computer Talks to Your Printer
The following sections introduce you to the method of data transfer
between your computer and your printer. This is not essential
knowledge to operate and fully use your QMS-PS 410 printer. This
information may help you to understand, however, the operation of
your printer.
When you enter data into your computer from the keyboard, it
performs rapid, complex calculations and compiles and correlates
data based on only two numbers, Øs and 1s.
Computers and printers exchange these Øs and 1s as on and off
signals. Ø is off and 1 is on. (This is why your printer’s power switch
has a 1 and a Ø.) Each signal is called a bit. Eight bits combined
form a byte. A byte, with various combinations of Øs and 1s, can
represent up to 256 characters, including upper and lower case
letters, numerals, punctuation marks, and symbols.
The QMS-PS 410 printer has three interface ports: serial, parallel,
and LocalTalk. A serial and LocalTalk cable transmit data one bit
at a time. A parallel cable transmits a byte (8 bits) at a time. This is
why the parallel interface is usually faster.
Your Printer’s Memory
The QMS-PS 410 printer receives data from your computer, stores
this data in its memory (called a buffer), and processes it using the
rules of the printer’s language.
Your printer has three types of memory: a permanent read-only
memory (ROM), a long-term memory (EEPROM) and a short-term
memory (RAM).
Appendix E
Computer Literacy E-1