History of the IBM PC: 42 Years Ago – Why It Was So Important



Forty-two years ago, the IBM PC was released.

On August 12, 1981, IBM announced its first “personal computer,” though it had previously been famous for its IBM System/370 mainframe computer. I operated one of these mainframes in a raised-floor data center in the early ’80s.

The PC was officially called the IBM Model 5150 and sported a 4.77 MHz Intel 8088 microprocessor. It had been in development for a year in a secret “skunkworks” lab in Boca Raton, FL, under the direction of Bill Lowe.

It cost $1,565 and targeted consumers and professional users, especially students (who could afford it) and business users. In today’s dollars, it would have cost $4,455.

Back in the day, I  watched someone who knew how to use a VisiCalc spreadsheet build a software pricing forecast for me on the “green screen.” His fingers flew over the keyboard. It was amazing.

Did it catch on?

The PC exceeded IBM’s expectations by over 800%!

IBM was shipping 40,000 PCs a month, which was a lot then, with over half going into homes. IBM licensed the character of Charlie Chaplin‘s “The Little Tramp” for their advertising campaign.


IBM PC Operating System

Microsoft worked with IBM to produce the PC DOS operating system; a variant was later called Microsoft’s MS-DOS (Microsoft Disk Operating System). The first IBM system could also run two other operating systems: the CP/M-86 and the UCSD p-System (Pascal). However, because CP/M was unavailable for six months, it was rarely ordered. The PC included the IBM BASIC programming language, similarly licensed from Microsoft.


Thanks for the Memory

It had 16 KB (kilobytes) of memory but could be expanded to 640 KB. Who could need more?

By comparison, today’s Apple Watch has at least 2 GB or roughly six orders of magnitude more memory.






The system motherboard’s Read-Only Memory (ROM) had four chips to hold the Cassette BASIC and one chip to hold the BIOS (Basic Input/Output System).


Diskettes or Floppies?

Though the first IBM PC came with up to two 5.25″ diskette drives, in 1981, Sony introduced the first 3.5″ diskette and drive. The name “floppies” soon displaced it.

Hewlett-Packard first adopted it for general use in 1982 and built momentum for the format, and helped it beat out other “microfloppy” standards like the 3″, 3.25″, and 3.9″ formats.


Not the First PC

Apple II


In 1977 Apple released its Apple II — spelled out as apple ][. This personal computer competed with the Commodore PET and the TRS-80 (sold through RadioShack), but Apple had the distinction of supporting color (via an RCA connector that supported NTSC video.) Apple also had a newly redesigned color logo at the time.

But the IBM PC was different. I recall declaring at the time that IBM’s entry into the market

“legitimized the desktop microcomputer market”

in a way that the other players had not. Though the other PCs were indeed “personal computers,” they were often used only by hobbyists. The IBM PC was used in business and the home.


Apple Macintosh

However, it had a character-based interface and screen. It would not be until the Apple Lisa (that few bought in 1983 at $10K) and the more popular Apple Macintosh released in 1984 that a bit-mapped screen with a Graphical User Interface (GUI) would become popular.

Mice, windows, menus, icons, and “direct manipulation” of objects onscreen via a mouse pointer were now possible for the mass market. I brought my first Mac home in 1985. I still have it.

Admittedly, Steve Jobs may have “innovated” on some of these ideas he got from seeing the Xerox STAR workstation at their Palo Alto Research Center (PARC,) but he popularized and commercialized these ideas. See my article on the history of Macintosh for more details.


IBM PC Monitor(s)

greenscreen ibm pc

IBM-PC Green Screen

IBM did support a color display via CGA, but that monitor was not available for another two years. Instead, most people used the MDA monochrome display, the green-on-black screen.


80 Characters

Why was the monitor 80 characters wide? What’s the history behind that?

The so-called “IBM punch card” was 80 characters wide and 12-rows long. Early programmers (like yours truly) would type on a punch card machine keyboard (keypunch) the characters of a line of computer programming code, like FORTRAN. The machine would punch holes in the card that would be fed into a “card reader” and transferred to a computer.


IBM Punched Card

IBM Punched Card


I say “so-called” because it was patterned after the Hollerith card. Herman Hollerith was a Civil War veteran who worked at the US Census Bureau and filed a patent on his card, similar in design to those used in the Jacquard mechanical loom first demonstrated in 1804.


Jacquard loom

Jacquard loom


The loom was driven by Semyon Korsakov‘s punched card announced in 1832.

Hollerith’s card was used in the 1890 US census, reducing the time to collect information from 8 years to 6 years since the previous census effort in 1880. Data were entered by punching circular holes in a card and reading them with electromechanical tabulators. The card size matched that of American currency at the time so that that card would fit nicely into a wallet.


Hollerith Punched Card

Hollerith Punched Card

Nerd trivia:

Unix and Linux “terminal” windows are 80 characters wide by 24 (or 25) rows long.


The IBM PC “Clone Wars”

PC Compatible

IBM PC “Compatible”

Because IBM chose to use retail computer dealers for the first time, they insisted that IBM use standard off-the-shelf commodity parts rather than proprietary IBM-designed ones; this proved both a boon and a bane.

IBM had been using the 64-bit Intel 8088 processors; in 1986, the Compaq computer beat IBM to the punch and introduced the world’s first 80386-based PC, using an Intel processor with the power and design to run a GUI-based operating system. By this time, IBM’s PC sales were taken over by PC clone sales.

Additionally, no one calls them IBM PC Compatible computers anymore; now they’re called (Microsoft) Windows PCs. And as software is built to the operating system, the amount of software for the platform a year after its release was four times that of the amount of software for Macintosh available a year after its release.

In contrast, the Motorola 68000 family of microprocessors, which was not volume production-ready in 1981, became the favorite CPU of workstation companies like Sun Microsystems and Apple‘s initial line of computers.


Impact of the IBM PC on Computing

While mainframes, supermini computers, and workstations are still with us, their day in the sun has passed. The computer that most people are familiar with (and have) is the desktop or laptop computer. Bill Gates, the founder of Microsoft, stated many years ago that his vision was to have

“a computer on every desktop.”

It seemed unheard of then, but it wasn’t quite visionary enough. Now, most people have a “computer on their palmtop”; or a smartphone.

IBM’s original Press Release from August 12, 1981, is here.


Bill Petro, your friendly neighborhood historian


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About billpetro

Bill Petro writes articles on history, technology, pop culture, and travel. He has been a technology sales enablement executive with extensive experience in Cloud Computing, Automation, Data Center, Information Storage, Big Data/Analytics, Mobile, and Social technologies.

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