The Commodore PET/CBM 4000 series features the built in BASIC 4.0, along with more memory to make them more attractive to use in schools. Schools all over Canada and the United States used the PET computers.

To counter after market memory upgrades, Commodore sold PET 4008 and the PET 4016 models with the empty memory sockets punched out and destroyed. This encouraged those who wanted more memory to upgrade to the 4032, instead of soldering RAM chips themselves.

There were four models:

• CBM/PET 4008 - 8KByte RAM
• CBM/PET 4016 - 16KByte RAM
• CBM/PET 4032 - 32KByte RAM

The 6502 is an 8-bit MicroProcessor designed by MOS Technology. The team was led by Chuck Peddle and had also worked on the Motorola 6800. The 6502 is a simplified, but faster and cheaper design than the 6800.

The 6502 was introduced in 1975 and was the cheapest microprocessor on the market. Together with the Zilog Z80, the 6502 helped start the home computer revolution of the 1980s. The 6502 was used in a wide range of devices: the Atari 2600, the 8-bit Atari home computers, the Apple II, the Nintendo Entertainment System, the Commodore 64, the BBC Micro and many others. All used the 6502 or a variation of it.

The 6502 is a 1MHz design, while the 6502A is designed for 2MHz. The 6502A is 100% compatible with the original 6502.

Commodore soon bought MOS Technology, but conitnued to sell the microprocessor to competitors and licensed the design to other manufacturers.