The first computers made were big. Room size big. They were also very expensive and pretty slow and you had to be a specialist to program them. So the president of IBM, Thomas Watson, can be forgiven for his infamous quote from 1943:
"I think there is a world market for maybe five computers."
The first popular microcomputers
A microcomputer is defined as a computer with a single central processing unit (CPU) as a microprocessor.
The MITS Altair 8800 (1975)
Featured on the cover of the magazine "Popular Electronics" in January 1975 was the MITS Altair 8800, and this started the new era of the microcomputer. Limited as it were, it was still widely popular - though mainly amongst geeks. The MITS could be purchased as a DIY project, and when it was assembled, it had eight switches that could be used to program it. Each switch represented one bit in the memory register, and instructions were made one byte at a time.
As the microcomputers developed and became more advanced, they would have more memory and a built-in keyboard. They would also come with some sort of text-based interface – typically a specific flavor of a programming language like Basic or something similar.
The ZX81 (1981)
One of the most well-known microcomputers was the ZX81, which came out in 1981. This computer had a wide appeal even though it had no more than 1 Kb of RAM. Later extension modules became available so that you could upgrade to either 16 or 64 Kb. With so much RAM, you could type in 64.000 characters of computer code.
The ZX Spectrum (1982)
The ZX81 was followed by the ZX Spectrum in 1982. This one came with 16 Kb but could be upgraded to 128 Kb. In order to use it, one would have to connect it to a television, and the resolution you'd see would be 256 x 192 pixels, which equals to 32 characters across in 24 lines. The computer was able to show 8 colors and play five octaves of sound in mono.
Within the next couple of years, a myriad of microcomputers hit the market. They were now becoming known as home computers, and they include machines from well-known brands like Acorn, Amstrad, Atari, Commodore, Texas, and Sinclair. The most successful microcomputer by far was the Commodore 64. Two brands ended up stealing the scene - and the market: IBM and Apple.
The software operating system
A contester to the microcomputer was IBM's so-called Personal Computer or PC, although it was much pricier and did not find its way into ordinary homes straight away. The IBM PC used a software operating system. This had to load on startup but made it easier to update - simply because you did not need to buy a completely new piece of hardware.
The OS (Operating System) was called MSDOS; this was short for Micro-Soft Disk Operating System (yes, they used a dash in their name in the early days). The code was based on the UNIX operating system, although much simplified.
From calculators to communication devices
In the words of Bill Gates, the founder of Microsoft and the developer of MSDOS:
"I think it's fair to say that personal computers have become the most empowering tool we've ever created. They're tools of communication, they're tools of creativity, and they can be shaped by their user."