The Commodore 128 was introduced in 1985 an was intended to be both a replacement for the C64 as well as a machine capable of business applications. The C128 is both C64 compatible and able to run the CP/M operating system, the popular operating system on 8 bit business computers.
Processor: The C128 has two microprocessors, the MOS 8502 microprocessor as well as the Zilog Z80. Both microprocessors are capable of addressing 64k of RAM.
RAM: The C128 has 128k or RAM in two banks. This is done because both processors are only able to access 64K at a given time, therefore the computer only uses one 64K bank at a given time.
Keyboard: The C128 uses the same keyboard as the VIC20 and C64, but has additional cursor and number pad keys as well. The layout is the same as a typical computer or typewriter with a few exceptions. The Commodore keyboard has three keys between the "L" and the "Return", instead of the more typical one or two. While this doesn't present a large problem, it is sometimes is easy to miss the "Return" key. The Commodore keyboard includes most all standard ASCII characters, the only ones missing are characters 96 and 123 though 126 (`, {, |, }, and ~). Although not missing, there are some keys and characters that are different from the normal ASCII characters. The backslash (\) is replace with a British pound, and the underline (_) is replace with a back arrow. The keyboard does include standard control and shift keys, as well as a "Commodore" key that generates special characters or colors.
Video: The Commodore 128 has two totally separate video systems. One is the 40 column VIC chip (8564) which produces output for a composite monitor or TV set, as used in the C64. The other is the 80 column chip (8563) which produces output for an RGB monitor (Commodore Business Machines, p4). The output of the RGB chip is compatible with that produced by a CGA board on an IBM or compatible.
Storage: The Commodore 128 has an optional cassette interface connector for use with a special Commodore cassette recorder. While this interface does require a special recorder, Commodore has one of the most reliable cassette systems. Disk drives and printers are attached through a special serial interface. The drive that originally shipped with the C128, the 1571, is a double sided 40 track drive that uses both GCR and MFM encoding, which makes it compatible with C64 and CP/M disks. See compatibility below for more information on other disk drive options. (Commodore Business Machine Newsgroup).
NOTE: Due to similarities between Commodore machines, the following information is common to all Commodore machines listed on this site.