Microprocessors are electronic devices that perform calculations and control electronic operations. They are found in everything from computers to automobiles to home appliances. Microprocessors contain both combinational logic and sequential digital logic. Combinational logic performs arithmetic and logical operations, while sequential digital logic controls the order in which these operations are performed.
The first microprocessor was the Intel 4004, released in 1971. It had 2,300 transistors and could perform addition and subtraction with 4-bit words. The 4004 was followed by the 8-bit Intel 8008 in 1972, which could address 1KB of memory. The 8008 was used in early personal computers such as the Altair 8800.
In 1978, Intel released the 16-bit 8086 microprocessor, which had an instruction set compatible with their earlier 8008 processor. The 8086 was successful in commercial applications due to its pricing and availability from multiple sources. In 1985, IBM released the 32-bit IBM PC/AT based on the Intel 80286 microprocessor. This processor became one of the most popular architectures for personal computers until it was succeeded by processors with 64-bit architecture in 2003.
Today’s microprocessors are much more powerful than those of early personal computers. They can address far more memory (up to several gigabytes), execute instructions faster (several hundred million per second), and handle data types larger than 16 bits (or even 64 bits). Microprocessors are used not only in personal computers but also embedded systems such as automotive engine controllers, cellular phones, industrial robots, office machines such as printers and scanners, spacecraft flight controllers, digital TVs and many other devices