Nearly every microprocessor ever made hides inside a machine rather than a computer
In 2009 an estimated 98 percent of all microprocessors produced went into embedded systems, not desktops or laptops. These are small dedicated computers buried in washing machines, cars, traffic lights and MRI scanners, each doing one job, often against a strict clock, and usually without anyone noticing they are there.
An embedded system pairs a processor, memory and input and output hardware to perform a single function inside a larger device. Because the job is fixed, engineers can trim it for size, cost and reliability. Its software, called firmware, lives in read-only or flash memory and runs with very little memory and often no screen or keyboard at all. A Gibson Robot Guitar, for instance, contains one purely to tune the strings.
Early examples were military and space hardware. Autonetics delivered its D-17, which guided Minuteman missiles, in 1961, and its replacement for the Minuteman II in 1966 was the first high-volume use of integrated circuits. The Apollo Guidance Computer, developed around 1965 at MIT under Charles Stark Draper, was considered the riskiest item in the whole Apollo programme because it relied on brand-new integrated circuits to save size and weight.
Then chips got cheap. The Intel 4004 of 1971, the first single-chip microprocessor, was built for calculators but still needed separate memory. By the early 1980s memory and input and output had moved onto the same chip, creating the microcontroller. That let designers swap fiddly analogue parts like potentiometers for simple buttons read by software, putting most of the effort into code rather than circuitry.
Today they are everywhere. Cars rely on them for anti-lock brakes, stability control and traction control; aircraft use them for inertial guidance; factories, pipelines and power grids network many together. Tiny wireless sensors called motes can run on a battery for years. Isolated systems without network connections are harder to hack, one reason they suit aerospace and defence.
Source: Embedded system
