A mural dedicated to the history of Personal to Home Computers – story and rationale of each entry

BACK TO THE MURAL

Much has been written on the history of computers. The focus below will be to describe notes or rationale on why these entries were selected for the mural (and to avoid trying to repeat the technical or historical descriptions that are readily searchable).

TOP ROW

Punch Card
Punch cards have a long history, even before computers, perhaps even before the invention of the keyboard. They are included in the mural since even by 1970, they were still very much in use. Punch card equipment for computers from the 1950s was still widely available.
NOTE: The “chad” pieces from the punched dots were discarded into a “bit bucket.” See story here.
Fan-Fold Tape
Fan-folded paper tape was another popular form of punch card still in use by the 1970s (originating around 1960 on the PDP-1). However, it was not practical for large applications, and often replaced in a reel form.
NOTE: See here for thoughts on punch card. vs. paper tape.
9-Track Tape
The use of magnetic tape for data storage is a fascinating application of physics (see here). Use of reel-to-reel tape for computer data began around 1951 (see here). The 9-track tape became popular with the release of the IBM 360 in 1964 and continued to be used well into the 1970s.
8″ Floppy Disk
The 8-inch “memory disk” was never a popular format for personal or home computers. But it is depicted along the year of its introduction, since IBM offered it as an accessory to the IBM System/370.
QIC Tape
Like the 8-inch disk, the Quarter Inch Cartridge was also never a popular format for personal or home computers. The mechanism to operate them was bulky and the spindle inevitably required maintenance. But the performance and capacity was practical enough for some systems. Both the Tektronix 4051 and IBM 5100 use QIC DC300 tapes, and numerous HP portable computers use a smaller DC100 version.
Arrowhead Computer Co. The Computer Store
This photo represents the opening of the first computer store. There were radio stores, electronic stores, stereo and television stores. But for the first time, the idea of selling a computer in a retail store happened in 1975. No one quite yet knew what a computer-at-home would be used for, since very little software existed for the new microcomputers. And right away, there was drama in how the computer would be marketed, as certain vendors wanted to dominate these stores (encouraging a kind of “vendor lock” that the micro-computing industry was keen on avoiding). See the article here.
Paper Tape by Teletype ASR-33
Spools of paper-tape were a kind of hybrid between magnetic tape reels (in terms of being wound up and sat on a reel) and fan-tape (narrow paper with punched holes) and was most famously used to hold the original Altair BASIC written by Bill Gates (as one was dropped to the floor while Bill was distracted at a Club Meeting and a copy was made, prompting Bill’s historic Open Letter).
MITS Altair 680 BASIC on Audio Cassette
The exact origin of using standard audio-cassette tape as a computer data storage media is not clear. Cassettes that look similar to audiotape are seen in use by 1971, but they weren’t quite the same type of tape. But some time in 1976, the use of standard audio cassettes had become common practice as an inexpensive way to store data. Rates varied from 80-200 characters per second. This meant that with a 60-minute duration, cassettes would have more storage capacity than the early disk drives (but audio cassettes were not suitable for random-access, unlike the QIC cassettes and 9-track tapes that did have marked blocks).
5.25″ Floppy Disk
The 5.25″ floppy disk, introduced in 1976, was an obvious refinement of the 8″ format. The 5.25″ format was about the size of a tabletop paper napkin and the drives themselves were much more practical for desktop usage. The reason this icon is placed later near 1978 is because that is when the format was more practically available to microcomputers (in terms of drive controller hardware being available and the disk media itself).
NOTE: Also wanted to spatially separate the disk icon from the 1975 tape and cassette icons. Besides the media size, the other difference between 5.25″ and 8″ is the position of the small hole around the inner ring.
3.5″ Disk
The 3.5″ disk had a more solid case but was still referred to as a “floppy disk” (since the actual disk inside was still a flexible media). The 3.5″ format was decided by a consortium, and debut in the 1984 Macintosh with a capacity of 400KB. In later iterations, the 3.5″ disk format peaked at a capacity of 2.88MB in 1987. The “sliding door” kept dust (and sunlight) away from the actual disk, making it an overall much more durable and practical format storage media format welcomed by home computer users.

CENTER ROW (hardware)

Systems listed in the known order of product-release date.

DEC PDP-11From the beginning of the PDP-1 in 1960, the PDP was considered as a “personal computer.” Not a large batch processing system, but a system where a single user can sit down at a terminal and interact with the programming of that system. The PDP-11 was a 16-bit system (in contrast to DEC’s 18-bit PDP’s) and was used to pioneer the development of both Unix operating system and the C programming language.
Datapoint 2200The DP2200 had an 80×12 CRT and cost about $5000. It was not just a terminal, as it could be programmed (having the same instruction set as the Intel 8008). But it had limited bus expansion and no built-in software (aside from an assembler monitor with ability to load content from tape).
NOTE: See also Olivetti Programma 101 (curtamania.com)
IBM System/370When you consider the “minimal parts” of the S/370, it appears more like a minicomputer: a kind of typewriter for inputs, a processor box that fits along a table, and printer for output. In such a configuration, even the mighty IBM System 370 mainframe could be viewed as a personal computer – but probably no one bought or leased an IBM System 370 for use in that way.
NOTE: The prior model, the 1964 IBM S/360, was quite similar but had a white panel instead of black (for standard leased systems).
KINBAK-1
With only 40-50 units sold, it is a stretch to attribute much significance to the KINBAK-1. But the inclusion of the KINBAK-1 highlights that the very-idea of an affordable personal computer was “in the air.” Keep in mind that computing isn’t all about “interactive computing” (as is typically associated with personal or home desktop-style computing) but also huge application in “embedded computing” (using programmed-logic to control other machines).
Magnavox Odyssey
While not a general-purpose computer, the Odyssey is included in the mural to represent the early idea of connecting an electronic device to home televisions, to perform some interactive activity. There was some technical development in the video circuitry, which did influence the path of the first home computers that came later (such as the TRS-80, which saved cost by being adaptable to existing home television sets). The Odyssey therefore represents a notion of computer-like-devices having one step into the door of peoples’ homes via being connected to standard television sets.
NOTE: We get a kick out of putting the $100 Odyssey toy next to the $30,000 Xerox Alpha dream-machine.
NOTE: See also Don Lancaster “TV Typewriter”
Intel Intellec 8


The Intel Intellec 8 was an engineering reference for use by developers of embedded systems. While it is not really a personal computer in the same fashion as the other entries, it is included as a reminder that such reference equipment did exist and helped inspire the systems that did become personal computers.
HP9830A
The HP9830A had built in ROM BASIC, supported a top mounted printer, and a single row screen with full size keyboard. The single row screen simplified the power requirements and overall design complexity. This is included to reflect on that transition and blending of calculator-style devices with programmable devices.
Wang 2200
The original Wang 2200 had an external CPU and power supply. Soon after, the power supply was reduced in size and made internal to the main unit. But the CPU remained as a large external attachment. The system featured built in ROM BASIC, a multi-line screen, and cassette tape storage. But the design permitted only up to 32K RAM.
Xerox Alto
The Alto is a legendary ahead-of-its-time computer built in 1973, influenced by the 1968 Engelbart “mother of all demos” presentation. The Alto was not a mass-produced consumer product but was a proof-of-concept technology demonstration, which is why we debated on including it. If the Alto was not included, we probably would have instead used the space for the Mark-8 kit (which in my view is very fitting, since the “stacked board” design of the Mark-8 is so similar to the internals of the IBM 5100). Ultimately, we decided to go with the Alto in the mural, since it had such substantial influence on the GUI concepts that eventually emerged in home computer 10 years later.
Micral N

The Micral N (designed and built in France) is touted as the “first general-purpose computer powered with a microprocessor” and was based on the Intel 8008. Like the later Altair 8800, the Micral N could be expanded to have serial IO card, modems, tape or disk units, a display card, and keyboard — such that it could be expanded into a more interactive personal computer.
MCM/70
The MCM/70 is an impressive portable system that used an Intel 8008 and supported APL (with a cost of $4700 with the base 2K RAM). The single row plasma screen simplifies the necessary hardware, but the inclusion of the two cassette units makes this a very interesting system. Like the HP9830A, the style of the MCM/70 is still “undecided” between being an advanced calculator or a personal computer.
NOTE: What’s also interesting is the similarities that MCM/70 has with the early portable computers in 1983 (in terms of those first portables also using narrow screens).
MITS Altair 8800

The Altair 8800 is well known for being advertised in the magazine Popular Electronics in January 1975 as a kit for $439. This price, combined also with expansions options from the S-100 bus, made it a very popular system. Students and hobbyist could gradually “build up” to a more complete personal computer system, rather than having to purchasing something like a PDP-8 all at once. Or industrial developers could use the Altair 8800 nearly as-is for embedded applications.
NOTE: see also the IMASI 8080 clone of the Altair 8800 (a foreshadowing of what would later happen to the IBM PC).
IBM 5100

The IBM 5100 is a kind of “opposite” of the Altair 8800, in that at $20,000 it offers everything: mass storage, multi-line CRT, BASIC/APL, keyboard I/O, external monitor port, an extensive software library, and the option to act as a terminal to a variety of IBM systems. The IBM 5100 was never considered as a home computer, but the style makes it very familiar in form to what home computers did become: built in programming capability, front loaded mass storage, and support for a large screen to sit above the cabinet.
Tektronix 4051

This system is included because it was has ROM BASIC and is an early example of vector graphics.
Apple I

The Apple-1 was a kit, motivated by Wozniak’s desire to make a game system (recall he and Jobs had worked at Atari and designed the game Breakout). The system needed a power supply, keyboard, case, and had no expansion bus nor built-in software. As such, from the perspective of 1976, the Apple-1 was not very influential since it wasn’t very useful for either embedded systems or as a personal computer (only 200 were sold). Other more complete single board systems were also offered across different regions within this same year.
NOTE: A year later, the Apple II did offer an expansion bus.
MMD-1

These boards are included in the mural to depict that water-shed moment when the form of a desktop home computer appliance was about to emerge. The relative simplicity of a single board design was a necessary step to make factory-style mass-production of home computers possible.
KIM-1

The KIM-1 was used nearly as-is in the Commodore PET personal computer. The idea of there even being a market for home computers still hadn’t been fully identified yet (especially with no software library yet available). These early microcomputer systems were still viewed as advanced programmable calculators, hence why the initial Commodore PET 2001 included the calculator-style chicklet keyboard (which in hindsight was a bad call but was corrected a year later in the 40XX series update).
NOTE: The rest of the systems after the Commodore PET (up to the C64) all represent 6502-based (or similar) systems. The Apple-1 and MMD-1 are also 6502-based single board systems.
TK-80

The rest of the systems after the TK-80 (up to the ColecoVision) all represent Z80-based systems.
Sol-20

The Sol-20 was like a redo of the Datapoint 2200, except now using a microprocessor. The modernized components allow for a much more compact system which also included support for the S-100 bus. The bus expansion made it easy to add peripherals such as modems, serial I/O cards, and disk drives to the system. The Sol-20 is “almost there” as a home computer. The only missing aspect was deciding on a standard boot up ROM, since the Sol-20 only booted up to a primitive monitor program.
NOTE: One of the greatest aspects of the Sol-20 is that the standard case assembly included the use of walnut wood. That choice is perfect as it represents a kind of fusion between the old-world and the new-world that is about to happen (in terms of home-computing appliances).
NOTE: The position of the Sol-20 in the mural is intentional, as a pivotal moment in which home-computing is just about to go mainstream.
Commodore PET
The Commodore PET was introduced in January 1977. For the first time, a complete desktop-computer appliance is offered for under $1000. At $795, it offered a 9″ CRT, Microsoft BASIC (with floating point and full screen editing features), 4K RAM, tape storage and expansion bus (including IEEE-488).
CPU: MOS 6502
Apple II
The Apple II was introduced in mid-1977. The base 4K model was over $1200 and had an INTEGER-only BASIC, but the system offered a vector graphics mode. Bus expansion support was added to the motherboard. Like the Commodore PET, this was a complete product to be sold in retail stores, with warranty, customer service, and factory produced by 10,000’s.
CPU: MOS 6502
TRS-80
Introduced in August 1977, Tandy had developed an inexpensive but complete computer system (using a Z80 processor). The base 4K model was $600 (with monitor, that was really a re-badged TV), and included Microsoft’s floating-point capable BASIC in ROM.
CPU: Zilog Z80
Interact
The Interact is on the mural to represent one of several “almost was” systems of that time. Another example was the Sphere-1 and IMSAI (both from 1975). Financing and retail-store partners were critical aspects in deciding which of these early home-computer systems would survive.
CPU: Intel 8080A
Atari 400/800
The famous Atari 2600 is not included on this mural. If it were included, it would sit at the position where microchess is shown. But from all the success of the Atari 2600, Atari was able to then later introduce a more complete re-programmable computer system: the Atari 400 (4K model, with Atari 800 being the 8K model).
CPU: MOS 6502.
TRS-80 Model 3
While the TRS-80 Model 1 was very successful as a product, it did have some technical issues (resulting in the reputation of “Trash-80”). Tandy did develop and sell a Model 2 version that was designed for business owners. The Model 3 was not especially popular as a home-appliance, but it was successfully used at schools (by offering early networking features).
CPU: Zilog Z80
Tandy Color Computer
The Color Computer was targeted particularly to home users. While not as popular as the Apple II+ by this time, the Color Computer was an affordable alternative (having lower resolution and less bus expansion options).
CPU: Motorola 6809E
OSBORNE-1
Aside from resurrecting the idea of a “luggable” computer like the IBM 5100, the OSBORNE-1 is on the mural to represent the CP/M operating system. CP/M originated from 1974 using the Intel Intellec and was used on Altair 8800, Sol-20, and IMSAI systems (for those who could afford disk drives). Then CP/M was “almost chosen” by IBM for the IBM PC disk operating system.
CPU: Zilog Z80
NOTE: See also Compaq Portable (1982).
IBM PC 5150
The IBM PC of 1981 was not an immediate success, but it thoroughly established the form of a home desktop computer system: high resolution monitor, front loaded disk media, detachable keyboard, expandable well past 64KB RAM, an expansion bus all combined with a formal PC-DOS. It took a couple years of refinements (to BIOS and DOS), but the overall hardware architecture remained useful to millions of users for the next 10 years.
NOTE: The disk drives were still a luxury accessory, as the base $1500 IBM PC still only included cassette tape support.
CPU: Intel 8088 (4.77 MHz).
BBC Micro
Starting about 1980, the BBC did an outstanding job of public outreach to introduce microcomputing to the public. The “Acorn” series was very popular in elementary schools and had an elaborate networking capability.
CPU: MOS 6502
Commodore C64
The C64 remains beloved and popular to this day for its excellent SID audio chip capability. Originally priced at $595, a “price war” (mainly against TI) reduce this price to $200-$300 within a year later. The price war was a kind of revenge against what TI had done to the calculator industry nearly a decade earlier.
CPU: MOS 6502
ColecoVision
The ColecoVision is included on the mural only because room wasn’t available to accommodate the Atari 2600 (and we wanted to include at least one game system to represent the evolution of the Odyssey concept). The ColecoVision could be “converted” to a computer with an expansion called the Adam (with CP/M support).
CPU: Zilog Z80
Sharp PC-5000
While not the first portable to market, the Sharp PC-5000 was a rare system that used “bubble memory.” The PC-5000 included MS-DOS 2.1 support and shows a kind of “coming of age” of portable home computing. The idea had been so well defined by this point, companies like Sharp “had fun” with the concept to make niche designs.
CPU: Intel 8088
Tandy Model 100
The first portable computers were awkward designs, with limited screen sizes. The Tandy Model 100 could run 20-hours using 4xAA batteries and had a built in BASIC that could store to audio tape.
CPU: Intel 80C85
Apple Macintosh
The legendary Macintosh is intentionally located on the mural across from the Xerox Alto that inspired it. The GUI OS was greatly welcomed by non-technical computer users, especially graphic artist and desktop publishing offices.
CPU: Motorola 68000
Tandy 1000
IBM continued to improve upon the IBM PC in many ways in 1983 and offered the 80286-based IBM 5170 in 1984. But the Tandy 1000 is on the mural for several reasons: (1) to represent the success of “IBM PC clones” that began to be offered to consumers due to the “open-ness” of the PC-architecture. (2) the back story of how the Tandy 1000 far succeeded over the IBM PCjr, a reminder that not all the IBM products were successful. (3) That the overall design of the PC home appliance had now been settled: a detachable keyboard, front loaded storage media, and a monitor atop the “main CPU.” This overall style remained in fashion for over a decade, until “tower PCs”, USB or wireless keyboards, and USB “thumb-drives” or SD-cards replaced disks.

CENTER ROW (peripherals)

“Peripherals” is one aspect that sets a personal computer apart from an embedded system. These peripherals are additional devices that extend the system beyond its original capability. This involves a “bus” system or channel, where users can insert or attach the additional capability. These are examples of some of the earliest peripherals used by home computers:

DC Hayes Modem
Modems (modulator/demodulator) that exchanged digital information across analog phone lines had existed since the 1950s. This concept was brought to microcomputers in 1977, by DC Hayes who made the first board and defined a control protocol to setup, connect, and disconnect between modems (AT-commands, like ATH to hang-up, ATDT to dial touch-tone, etc.). This was first made for the Altair S-100 bus, followed by the Apple II bus.
PETUNIA
The PETUNIA represents one of the earliest microcomputer peripherals that wasn’t a disk drive. The PETUNIA was a kind of audio-card accessory to the Commodore PET, as there was a kind of “digital audio underground” keen to make use of microcomputers for new kinds of sound work. The PETUNIA was a pre-cursor to the more professional SID audio that Commodore incorporated later in the C64. The TRS-80 systems also had a SoundPak cartridge.
graphics tablet
As an example of another popular peripheral (see here), Apple introduced a graphics tablet in 1979. This was famously used by Roberta Williams to make the game Mystery House, one of the first “graphical adventures.” For other systems, there was the “Koala Pad.” The introduction of these kinds of add-on devices confirmed the versatility of the expansion bus systems, to add new equipment to the system that hadn’t been anticipated upfront.
NOTE: See also Sketchpad Demo 1963

CENTER ROW (software)

Summary of the software titles and why they are depicts on this mural…

Microchess
Microchess was developed by Peter Jennings as a capability demonstration of what the KIM-1 single board computer to do.
WordStar
“Word Processing” is different than “Desktop Publishing,” but they are related activities (word processing can be letters, legal documents, or articles that end up in published magazines). Computers had been used for these activities by the early 1970s (with interactive screens and keyboards), but WordStar was first to bring that capability to microcomputers.
VisiCalc
VisiCALC has a fascinating “origin story” with the concept being thought of during a university class lecture: when one cell of calculations is updated, automatically apply the change to all other cells. The means for doing this was by specifying a formula that related one cell to another.
Zork
Zork is a “text adventure” that describes scenes as you virtually navigate through the story. But the interesting part of the back story: Zork began on a mainframe system, developed and evolved by university students, and then became a commercial software title for microcomputers. English text takes considerable memory space, and so Zork requires a disk file system.
Mystery House
COMMBAT
Ultima
AutoCAD
AutoCAD is a world premier engineering tool that continues to be developed today. In addition to word processing, desktop publishing, and “number crunching” – CAD (computer aided design) also became out of the top staple applications of personal computers.
Flight Simulator
Flight Simulator continues to be developed today, representing one of the most realistic flight modeling experiences for home computers. Initially this was a “self booter” for the IBM PC. Like the typical “office suite” of software, Flight Simulator (and the idea of realistic motion simulators) represents another very useful application of computers.
Turbo Pascal
Pascal was a programming language developed by Niklaus Wirth in 1970. A decade later, Borland released Turbo Pascal (developed by Anders Hejlsberg) which was popular because relatively high-speed compiling and being fairly easy to learn (while also being more structured than BASIC, such that re-useable libraries could be produced).
dBASE II
dBase II was a very popular follow on to Wayne Ratliff Vulcan database program from 1979. The ability to relate information, and quickly sort and query that information, is the hallmark of what a database system provides.
MacPaint
MacPaint (and PC Paint of the same year) marked the beginning of what is now typical paint software: circles, rectangles, lines, fonts, fill patterns, all interactively drawn using a mouse.
M.U.L.E.
MULE is a very popular multi-player game that was ported to multiple platforms.
ARCHON
ARCHON involved some action, but like MULE also has a strategy element. Both MULE and ARCHON represent the evolution of classical “board games” over to more expansive domain of computers.
Atari E.T.
The Atari game ET represents one of the first collaborations between Hollywood movie releases and game launches. While not the greatest of games, it was a complete and representative game that wasn’t half bad (at least in terms of sales). But what the ET game revealed was the trouble of ROM cartridge releases, where one has to predict/estimate how many cartridges to produce (i.e. how popular a software title will be for a particular season). This estimate was so far off for ET, that years later a large quantity of ET ROMs was famously found in a landfill.

BOTTOM ROW

The background of the bottom row in this mural represents silica sand (silicon) that used to make microprocessor.

Intel 8008
One of the first things to know about the Intel 8008 is that it was NOT a follow-on to the Intel 4004.
Motorola 6800
Intel 8080
MOS 6502
Zilog Z80
Motorola 68000
Intel 8088
Intel 80286
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