The Altair 8800 arrived in 1975 as the first personal computer

The Altair 8800, released in January 1975 by MITS (Micro Instrumentation and Telemetry Systems), is widely recognized as the first personal computer. It cost $395 for the kit version (about $2,300 in today's money) and came as an unassembled collection of parts that buyers had to solder together themselves. The machine had no keyboard, no monitor, and no disk drive — just a metal box with toggle switches on the front and rows of lights that blinked to show the computer's state.

The Altair ran on an Intel 8080 processor and came with 256 bytes of memory, which is roughly the size of a single paragraph of text. Users entered programs by flipping switches in binary code, one bit at a time. Despite these severe limitations, the Altair sold thousands of units and sparked the personal computer revolution. Two young programmers named Bill Gates and Paul Allen wrote a version of the BASIC programming language for the Altair, which became the foundation of what would become Microsoft.

Key Takeaways

  • The Altair 8800, released in January 1975, is considered the first personal computer and cost $395 as an unassembled kit.
  • The Altair had no keyboard or monitor and required users to enter programs by flipping toggle switches to input binary code.
  • The machine contained only 256 bytes of memory and ran on an Intel 8080 processor, making it far less powerful than a modern smartphone.
  • The Altair's success attracted Bill Gates and Paul Allen to write BASIC software for it, which led to the founding of Microsoft.

What made the Altair different from earlier computers

Before 1975, computers were room-sized machines that cost hundreds of thousands of dollars and belonged only to universities, governments, and large corporations. The ENIAC (Electronic Numerical Integrator and Computer), built in 1946, weighed 30 tons and consumed 150 kilowatts of electricity. The IBM System/360, introduced in 1964, was still the size of a refrigerator and cost over $2 million.

The Altair was different because it was small enough to fit on a desk, affordable enough for hobbyists to buy with their own money, and straightforward enough that an amateur could understand how it worked. It was not the first computer to use a microprocessor — that was the Intel 4004 in 1971 — but the Altair was the first to package a microprocessor into a complete, purchasable computer system designed for individual users rather than institutions. The machine proved there was a market for computers that ordinary people could own.

The Apple II and Commodore 64 made personal computers practical

The Altair was a landmark, but it was not a machine most people could actually use. The real shift toward computers in homes came with the Apple II, released in April 1977 by Steve Jobs and Steve Wozniak. The Apple II came fully assembled, included a keyboard and color graphics, and could run software like VisiCalc, the first spreadsheet program. It cost $1,298 and sold hundreds of thousands of units.

The Commodore 64, released in 1982, became the best-selling personal computer of the 1980s. It cost $595, came with 64 kilobytes of memory (256 times more than the Altair), and included a color monitor and joystick. By the mid-1980s, personal computers had moved from hobbyist kits to household appliances. The IBM PC, released in 1981, established the standard that most computers still follow today.

Why 1975 matters even though earlier machines existed

Historians sometimes point to earlier machines as "first" — the ENIAC in 1946, the Univac in 1951, or even mechanical calculators from the 1800s. But those were not personal computers. A personal computer is one that an individual can own, operate without specialized training, and afford with personal savings. By that definition, the Altair 8800 in 1975 was genuinely the first.

The Altair also arrived at the exact moment when the technology became cheap enough and small enough to make personal ownership possible. The Intel 8080 processor cost less than $200, and the rest of the components were standard electronics that hobbyists could buy from catalogs. A few years earlier, the same computer would have been impossible to build affordably. A few years later, computers were so common that the achievement seemed obvious. The Altair hit the narrow window where it could be both revolutionary and achievable.

How the Altair launched the personal computer industry

The Altair's success in 1975 triggered a wave of similar machines. The IMSAI 8080 arrived later that year, followed by the Commodore PET and the Apple II in 1977. Magazines like Popular Electronics and BYTE began publishing in the mid-1970s to cover these new machines. Computer clubs formed in garages and basements across the United States, where hobbyists shared code and hardware designs.

The Altair also created the first software market. Because the Altair was programmable and had a user community, people began writing programs to sell. Gates and Allen's BASIC interpreter for the Altair was one of the first commercial software products. This established the pattern that would define the personal computer industry: hardware manufacturers sold machines, and software companies sold programs that ran on them. Without the Altair proving that market existed, the software industry might never have developed the way it did.

The Altair's limitations show how far computers have come

Using an Altair 8800 by modern standards would be nearly impossible. There was no screen to see your work — you toggled switches and read the output from blinking lights. Programs had to be entered in hexadecimal code, a numbering system that uses 16 digits instead of 10. Saving your work meant writing the code down on paper or using an optional cassette tape drive that was slow and unreliable. A single program might take hours to enter and debug.

The Altair's 256 bytes of memory could store roughly 50 words of text. A modern smartphone has about 128 gigabytes of storage, which is roughly 500 million times larger. The Altair's processor ran at 2 megahertz; a modern processor runs at 3,000 to 4,000 megahertz. Yet the Altair was revolutionary because it proved the concept worked and inspired the engineers and entrepreneurs who built the machines that followed.

Frequently Asked Questions

Was the Apple II the first personal computer?

No. The Apple II, released in 1977, was the first personal computer that was practical and straightforward to use for non-technical people. But the Altair 8800 arrived two years earlier in 1975 and is recognized as the first personal computer, even though it required technical skill to operate.

Did IBM invent the personal computer?

IBM released the IBM PC in 1981, which became hugely successful and established the standard that most computers still follow. But IBM did not invent the personal computer — the Altair, Apple II, and Commodore machines all came before it. IBM's contribution was making personal computers a standard tool in business.

Could you actually use an Altair 8800 to do real work?

Yes, but it was difficult. Programmers used the Altair to write code, run calculations, and store data on cassette tape. The machine was powerful enough for serious work, but the lack of a keyboard and screen made it slow and tedious compared to computers that came even a few years later.

How much would an Altair 8800 cost in today's money?

The kit version cost $395 in 1975, which is roughly $2,300 in today's dollars. The assembled version cost $495, or about $2,900 today. That was expensive for a hobby computer, but affordable compared to the hundreds of thousands of dollars that earlier computers cost.