The Apple I, sold as a kit computer, was designed by a genius named Stephen Gary "Woz" Wozniak. It was designed over a period of years from parts Woz had free access to at his job as a Hewlett Packard engineer. HP encouraged its engineers to use company stock and lab facilities to experiment with new and interesting technology. Woz took full advantage of this privilege and when he got his hands on a MOStek 6502 had all the parts he needed to build the Apple I. It debuted in April 1976 at the Homebrew Computer Club in Palo Alto, but few took it seriously. The Apple I was based on the 6502 chip, whereas most other Homebrew computers were built on the Intel 8080 chip. The Apple I was sold through several small retailers, and included only the circuit board. A tape-interface was sold separately, but you had to build the case. Its initial cost was $666.66.
Read more about the Apple I, see this article: The Apple I
In 1977, the newly formed Apple Computer, Inc. introduced the Apple II for $1,298. It was not a kit computer like the Apple I but a completely assembled computer with a plastic molded case. The Apple II had a completely redesigned motherboard with a larger ROM, more expandable RAM (4K to start), and 8 expansion slots. It had the ability to display color graphics, a rarity at that time. It had Integer BASIC hard-coded on the ROM for easier programming, and included two game paddles and a demo cassette. In early 1978, Apple released the Disk ][, an inexpensive external disk drive that connected to the Apple II through an efficient controller card designed by Wozniak. The Disk ][ was a great improvement over audio cassette storage. The Apple II was replaced with the Apple II Plus in 1979. The Apple II Plus had more RAM (48K to start, 64K max) and a new auto-start ROM for easier start-up and screen editing. The Apple II Plus was replaced with the Apple IIe (e for extended) in 1983.
Released in early 1983, the Apple IIe was to be one of the most successful Apple computers ever. The computer was built around the new 6502A chip, which ran at a blazing 1 MHz. The IIe originally sold for $1,395 and had a number of improvements to its motherboard and casing until it was discontinued in 1993. It shipped with 64K standard RAM but could be expanded to 128K with up to 4 MB possible via third-party RAM boards and software. It was the only Apple computer to be in production for more than 10 years. The final form factor of the IIe was to be the Apple IIe Platinum. It debuted in 1987 and had an updated keyboard with a 10-key pad based on the Macintosh keyboard layout.
Changes introduced in the IIe Platinum were mostly cosmetic and superficial, with the biggest difference being that the case color was changed from beige to a blue-gray color Apple coined to be platinum. The motherboard was functionally identical to the Apple IIe Enhanced (released in 1985 as an update to the 1983 IIe), with fewer, more powerful chips. Like the IIe Enhanced, the IIe Platinum used the 65C02 chip. The Platinum shipped with 128K RAM as standard.
Introduced in April 1984, the Apple IIc was for all practical purposes the same as the Apple IIe but with one significant difference, it was compact and luggable. Steve Jobs had much to do with its design and many of its attributes appeared later in the Macintosh. One could say that the IIc was a "Job-so-fied" IIe. It was first and foremost a closed system, while the Apple IIe was an open system. The Apple IIe had expansion slots for adding things like a printer card, a modem card, or a mouse card. The Apple IIe came bare from the factory and had to be configured with cards in order to give it functionality.
Apple IIe Platinum
The IIc (the 'c' stands for 'compact') was designed to get down to business straight out of the box. It had no expansion slots but came with most anything anyone at the time could imagine to put in any free slot available on the IIe. The IIc came with the following ports standard: mouse (or joystick), modem, RF modulator port, RCA jack, disk drive, and printer port. Apple bundled the IIc with a miniature 5-inch, high-resolution green monochrome monitor (with an expensive, thin LCD monitor available as an option). It was designed to be portable with many third-party carrying bags available. Apple also produced some really good composite color monitors that were compatible with any of the computers of the Apple II family. As with the IIe, the IIc could be hooked to a television via an RF modulator or through an RCA jack. Early versions could not be expanded past 128K RAM without a third-party solution, but later versions had a 34-pin socket for expanding memory up to 1 MB. The IIc had a built-in 5.25 inch floppy disk drive and Apple sold an external IIc-styled disk drive called the Disk IIc as a configuration option.
The IIc shipped with a custom disk utilities floppy disk. The IIc's disk utilities made things like formatting disks (in DOS or ProDOS), copying disks, copying/deleting files, identifying the contents of a disk, and configuring the printer port or modem port very easy. It was far easier to use than DOS or ProDOS alone because the user did not need to learn text-line commands to use it. Unfortunately, the IIc did not sell as well as the IIe. Potential customers looked at its small size and equated that with less worth. In the 1980s, compactness did not necessarily denote quality to most people.
The Apple IIc was replaced by the more powerful Apple IIc Plus in September 1988. The IIc Plus had a 65C02 processor that ran at a user-selectable, 1 MHz or 4 MHz. Apple replaced the internal 5.25 inch disk drive on the original IIc with a 3.5 inch 800K floppy disk drive. The IIc Plus originally sold for $675. Apple discontinued the IIc Plus in September 1990.
The Apple IIgs ("gs" stood for graphics and sound), introduced in September 1986, was a quantum leap ahead of the earlier IIe or IIc form factors. It was the end of the line for the Apple II family of computers. Although strictly speaking, the IIc Plus was the last Apple II computer introduced by Apple, the IIgs is arguably the most advanced and for many, it represents the pinnacle of the Apple II family. Woz himself contributed to its design and later lent his name to a limited run "Woz Special Edition IIgs." The IIgs had a graphical operating environment with a Finder very similar to the Mac OS Finder. It was a 16-bit computer while the earlier IIe and IIc were 8-bit computers. Apple introduced a 16-bit version of ProDOS as the IIgs' primary disk operating system. The IIgs had a custom digital oscillator sound chip that could produce up to 15 musical "instruments."
Unlike previous Apple II computers, the IIgs had a detached keyboard and mouse attached thru ADB (Apple Desktop Bus), which later found its way to the Macintosh platform. ADB was similar to PS2 used in the IBM compatibles. ADB added quite a bit of functionality to the system and was used to connect the keyboard, mouse, or other peripherals. The IIgs shipped with a powerful BASIC compiler. Previous IIs used an interpreter, primarily because it tasked the system less and was easier to design in the original Apple II firmware. IIgs BASIC provided many more options and command words than the earlier Applesoft BASIC due in no small part to the increased capabilities of the hardware. The IIgs remained in production until it was quietly retired in December 1992.