As home computers rapidly gained in popularity in the early 1980s, third-party peripheral manufacturers also began selling peripherals. For those users wanting to do "serious work", the essential peripherals were floppy drives, modems, and printers. Unlike floppy subsystems, which tended to be machine-specific and 1st-party, the modem and printer markets tended to have major 3rd-party vendors like Epson, Hayes, and U.S. Robotics.

Which computer known for selling to home users was the first to include, as standard equipment, both a modem and printer port (two ports) suitable for 3rd party modems & printers of the time?

NOTE: Ports themselves have to be electrically compatible; requiring no more than a passive cable/adapter and software to use the modem/printer.

NOTE 2: I don't know whether the answer is the same as the first home computer to include 2 RS-232 and/or Centronics compatible ports. Maybe a different port type was supported by 3rd-party peripheral makers beforehand.

  • 2
    Mind to specify what exactly constitutes a "modem port" and a "printer port" in context of this question? Is it about a build in modem or (just) a serial port? Likewise for printer, what kind of port for which printer - as there were various connections available). If it's just about (serial) ports, then the question would be simply about the first machine with a (switchable) port, wouldn't it? (Not to mention, where to draw the line about being a home computer).
    – Raffzahn
    Jul 1, 2022 at 18:37
  • 1
    @Raffzahn Rather than specifying RS-232 and Centronics, I'm leaving it open to the possibility that some other port-type was available on both computer and 3rd-party peripheral sooner.
    – Brian H
    Jul 1, 2022 at 19:01
  • 3
    A plain old RS-232 port can function as a 'modem port' and a 'printer port'.
    – dave
    Jul 1, 2022 at 20:07
  • 1
    Agree with Raffzahn: the question is currently vague. Do the "printer" and "modem" ports need to be marketed as such, or would anything that theoretically qualifies okay? Does support for a printer and modem need to be built-in to the software?
    – DrSheldon
    Jul 1, 2022 at 23:57
  • 1
    I would consider a "modem port" something that would accept a telephone plug. "Serial connector" would be better. Jul 2, 2022 at 8:22

4 Answers 4


According to this page the Sol 20 included:

Ports: serial, parallel, cassette

and according to Wikipedia:

Cassette, parallel and serial ports extended off the back of the motherboard into holes in the case.

Not clear exactly which varieties of serial and parallel ports, but generally speaking in the good old days, parallel was something close to Centronics (and good for printers) and serial was something close to RS-232 (and good for modems, which meant an acoustic coupler at 300bps).

Update: Found the SOL-20 manual, which states:

It features both parallel and serial communications interfaces

Parallel interfacing is 8 bits each for input and output plus control handshaking signals, and the output bus is tristated TTL for bidirectional interfaces. The serial interface circuit includes both asynchronous RS-232 and 20 mA current loop provisions, 75 to 9600 baud (switch selectable).

Unlike some other early systems, it included a built-in keyboard and video interface, making it more like a typical "home computer" (Apple ][, Atari 400/800, C64, etc.) and therefore did not need the serial port for a terminal, unlike a lot of earlier (and later) S-100 bus machines. Released in 1976 (numerous web sites, plus copyright date of the manual), it predates Apple ][, TRS-80, Commodore Pet, etc.

  • In photos, it looks like any ports would be coming off of slotted expansion cards, but maybe not.
    – Brian H
    Jul 1, 2022 at 19:57
  • 4
    It was an S-100 machine, so I think just about everything was on a card. The question is what cards were included in the standard configuration. An IBM PC had video on a card, but it always came with a video card (it was a card so you could pick monochrome vs color) Jul 1, 2022 at 20:03
  • 1
    The SOL has a motherboard (visible here) which includes the video interface as well the serial ports - after all, being an all in one terminal was the very basic idea of the SOL. The S100 raiser board is what separated the SOL-20 from a SOL-10.
    – Raffzahn
    Jul 1, 2022 at 20:19

Home computer and interface is a bit vague, but since it's about arbitrary interfaces (*1), I'd give the

  • Olivetti 6060 (1975)
  • IBM 5100 (1975)

While these two had only a limited number of third party printers/modems attached, the

  • HP 9800 series (1972 onward, followed by the HP80 in the 1980s)

was quite famous with its HP-IB for connecting to everything from multimeters to disk drives. Many companies implemented HP-IB with their devices tapping the high end HP market, promising a fine ROI. HP-IB has been around as (GPIB or IEEE488) since the 1960s, so the number of devices from third party manufacturers is next to endless.

Or, if it's about microprocessor based systems I'd start with

  • Apple II. (1977)

This may sound strange at first, but since the type of interface was, for the question, explicit defined as open for all, the Apple II bus will quite do it. Especially considering that not only Apple offered printers to plug in there (Apple Silenttype) but as well third party, like EPSON.

It was followed shortly later by the

  • Commodore PET (1977)

offering a (mostly) HP-IB compatible bus, thus able to use a vast array of HP-IB compatible third party devices including printers and modems over this interface.

Now if this is really to be restricted to computers explicit designed and sold as home computer (*2), already the second (*3) on that list, the

  • Atari 400/800 (1979)

will make a good case, as there again a countless number of SIO compatible third party devices have been made.

*1 - Comment by Brian: "I'm leaving it open to the possibility that some other port-type was available on both computer and 3rd-party peripheral sooner"

*2 - Excluding computers that have been made as trainers, school devices or otherwise for a general audience (personal computer), leaving only machiens explicit made and marketed for home use with an emphasis on games, etc.

*3 - The first pure home computer is eventually the TI 99/4.

  • 1
    @BrianH What's the difference between a 'slot' and a 'port'. Commodore called the PET's bus as well port, didn't they? Or is a slot made due using a receptacle ? Because than RS-232 would as well be a slot, wouldn't it?
    – Raffzahn
    Jul 1, 2022 at 19:36
  • 1
    You had an HP9800 for your "home" computer? Where'd you grow up, the Xavier School for Gifted Youngsters? (If so I know what your gift was: writing long interesting useful answers to retrocomputing questions ...)
    – davidbak
    Jul 1, 2022 at 20:16
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    @davidbak Iwish (and thanks for the kind words). I included it rather because 'homecomputer' is not a useful term to classify, except going for truly dedicated ones, which in turn would exclude machines like PET, TRS-80, Apple or any S100.
    – Raffzahn
    Jul 1, 2022 at 20:53
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    @BruceAbbott This writeup is maybe fine as introduction to an idea for a wiki article, but isn't a useful definition here, as it's an ambiguous one. The mentioned Apple II being a great example of being targeted to different markets at the same time. Marketing is variable and eager to please everyone. A term used in context of a question to describe the valid answers must not be ambiguous. To make a distinction to in- or exclude machines only clear design features (technical or otherwise) work.
    – Raffzahn
    Jul 2, 2022 at 8:44
  • 1
    @BrianH you seem to be asking when serial and parallel port interfaces were built onto the motherboard (which excludes all the really early backplane systems which had no motherboard).
    – RonJohn
    Jul 5, 2022 at 3:29

For almost any kind of expansion connector a computer could possibly have, one could construct a printer that would interface to it, and for many possible connectors interfacing a modem would also be possible. Even a relatively primitive cassette interface could be made to accomomdate a purpose-designed 300-baud modem with a few transistors, resistors, capacitors, and a small microcontroller as a bridge (something like the one in a Simon(R) brand electronic toy would probably suffice).

It's somewhat ironic in retrospect that if something like the 1526 or 1540 disk drive--both designed as new products in 1980 for use with the VIC-20, had been designed to require a plug-in cartridge, they could have been made both cheaper and better, but from a marketing perspective it was better to have the VIC-20 include a "serial port" that could interface "directly" with a printer and disk drive. As an added irony, btw, it's possible to interface a VIC-20 or C64 to a standard Centronics printer using a cable connected to the user port and using software that's designed to work with that. Easy Script could be used in that fashion, but unfortunately many other programs could not.

  • It's certainly true that lots of enterprising small companies filled the niche to create active devices that adapted Commodore's 8-bit machine ports to various 3rd-party peripherals. It's one of the things I hated about Commodore's early machines,
    – Brian H
    Jul 1, 2022 at 19:53
  • @DrSheldon: My main point was that the question of whether a computer's built-in hardware could be used to connect a modem or printer was as much a question of what devices were built to interface with whatever kind of connections a computer happened to offer. While the RS-232 DB-25 serial-port connector and 36-bit Centronics connector emerged as standards, the question didn't ask about them in particular, and it wasn't uncommon for modems and printers to be constructed to interface with particular computers.
    – supercat
    Jul 2, 2022 at 3:04
  • @DrSheldon: If the VIC-20's user port would have been capable of interfacing to a Centronics printer using nothing but a cable that rearranged the pinouts to fit but had no other electronics, but nobody bothered to do such a thing until after the C64 was introduced, would that count as the VIC-20 having a Centronics-compatible printer port?
    – supercat
    Jul 2, 2022 at 3:05
  • CBM's "IEC serial" bus was not just a marketing thing; it also allowed them to re-use a significant amount of firmware and keep compatibility with existing software designed to access devices via CBM's KERNAL interface.
    – cjs
    Jul 2, 2022 at 5:55
  • @cjs: I would think the decision to solder the DIN connector onto the motherboard rather than omitting the connector but instead selling an expansion-port cartridge with an interface that would work with existing PET peripherals was driven by a marketing desire to claim the interface was "built in". Using an expansion ROM to handle the GPIB-style logic would have made a little more room available to include some improvements in BASIC, such as making POKE accept multiple arguments (stored to consecutive addresses), or having PEEK() with nothing between parens read the byte after the last one.
    – supercat
    Jul 4, 2022 at 0:33

While not really a home computer (the distinction was not that existent at that time) the French built Goupil G1 from 1979 could be a contender as it is probably one of the first computer with an integrated modem (acoustic coupler).

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