The 65C02 Microprocessor is a slightly upgraded version of the popular and venerable 6502 microprocessor. The 65C02 shared its predecessor's 8-bit instruction set architecture and 16-bit memory addressing. While the redesign was made by Bill Mensch of Western Design Center, the 65C02 was likewise manufactured by other semiconductor companies such as NCR, GTE, Rockwell International, SynerTek and Sanyo. The MOS Technology 6502 is an 8-bit microprocessor designed by MOS Technology in 1975. ... Microprocessors, including an Intel 80486DX2 and an Intel 80386 A microprocessor (abbreviated as µP or uP) is an electronic computer central processing unit (CPU) made from miniaturized transistors and other circuit elements on a single semiconductor integrated circuit (IC) (aka microchip or just chip). ... 8-bit refers to the number of bits used in the data bus of a computer. ... An instruction set, or instruction set architecture (ISA), describes the aspects of a computer architecture visible to a programmer, including the native datatypes, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O (if any). ... In computer science, 16-bit is an adjective used to describe integers that are at most two bytes wide, or to describe CPU architectures based on registers, address buses, or data buses of that size. ... Bill Mensch is the inventor of the 65C02, and W65816 derivatives of the famous MOS Technology 6502 microprocessor, and head of the Western Design Center. ... If you were looking for the Western Digital Corporation, see Western Digital. ... A semiconductor is a material that is an insulator at very low temperature, but which has a sizable electrical conductivity at room temperature. ... NCR Corporation is a technology company, specialising in solutions for the retail, and financial industries, as well as decision support systems. ... This article or section should include material from Bell Atlantic This article or section should include material from GTE Verizon Communications (NYSE: VZ) is a local exchange telephone company formed by the merger of Bell Atlantic, a former Bell Operating Company, and GTE, which was the largest independant local exchange... Rockwell International was the ultimate incarnation of a series of companies under the sphere of influence of Willard Rockwell, who had made his fortune after the invention and successful launch of a new bearing system for truck axles in 1919. ... Categories: Corporation stubs | Companies of Japan | Companies traded on the Tokyo Stock Exchange ...

The 65C02 added a small number of documented opcodes and, significantly, fixed the irksome 'indirect jump page wrap bug' that caused fits for so many budding assembly language programmers. A computer can perform operations, each of which is assigned a numeric code called an opcode. ... A computer bug is an error, flaw, mistake, failure, or fault in a computer program that prevents it from working correctly or produces an incorrect result. ... Assembly language or simply assembly is a human-readable notation for the machine language that a specific computer architecture uses. ... In computing, a programmer is someone who does computer programming and develops computer software. ...

Another problem with the 6502, fixed in the 65C02, relates to its program status register, which contains eight system flags. Some flags are set or reset under program control. Others reflect the status of the machine after mathematical instructions:

• N Negative sign flag
• V Overflow flag
• 1 Always 1
• B Break flag, set by the BRK instruction
• D Decimal mode flag
• I IRQ disable flag
• Z Zero flag
• C Carry Flag

In the 6502 the decimal flag (D) was not initialised during a reset. This meant it would be in an unpredictable state after a reset, and could lead to arbitrary behaviour. This forced programmers to use CLD instructions after resets on all 6502 programs.

Notable uses of the 65C02

• 2nd generation Enhanced Apple IIe computer.
• Apple //c portable computer.
• In the TurboMaster 4.09 MHz accelerator cartridge for the Commodore 64.
• BBC Master home computer.

The Apple II was one of the most popular personal computers of the 1980s. ... The Apple II was one of the most popular personal computers of the 1980s. ... A megahertz (MHz) is one million (106) hertz, a measure of frequency. ... Close-up of C64 Commodore 64 (C64, CBM 64) was a popular home computer of the 1980s. ... A BBC Master 128 with monitor and disk drives. ...