What are Microcontrollers?
A Microcontroller is a complete, miniatuarized computer system on a single silicon chip, and typically, encased in a small black epoxy enclosure.
CPU – technically similar to a Pentium Processor, but not as powerful.
RAM – technically similar to a DDR3 memory module, but much much less. Typically just a few kilobytes but it could be upto a megabyte.
FLASH memory – technically similar to an SD card- but counted in kilobytes. This is where the executeable software is stored.
The cost of a microcontroller is $1 to a few dollars only. They take very little space, and can work from batteries a long time.
In the 1990s microcontroller revolution started- onchip FLASH memory became available, and costs dropped. Before of that, EPROMs were used. You can sometimes see these older chips with a glass window on the top. They take 1/2 hour or more to erase each time!
During developement, typically a controller in a prototype circuits is programmed, erased, and reprogrammed quite a few times. Increasingly, since powerful PCs are available now, also software simulation is used to save the time and efforts to program the chips.
Many household appliances these days have a microcontroller inside. They have first appeared inside Video recorders in the 1980s. However, these were mask programmed in the factory (the firmware can not be changed). PCs also contain microcontrollers- for instance, every SD card has one, and every hard drive, and so on.
One well known platform for schools, and hobby use is the Arduino. It is a circuit board based on an Atmel controller chip, and it contains a power supply circuit. There are software libraries available, so if you for instance want to use a small LCD, you dont need to write all the software. See here: http://arduino.cc