Computer

A computer is a machine that carries out a sequence of instructions.

While most people think of computers as machines that only do information processing, such as Laptops and Servers, but there is also a category called "Embedded Computers" or Embedded Systems. In Embedded Systems, the computer is used for a very specific purpose, which is typically to control the device of which it is a part.

Embedded Systems span a wide range, from small medical devices, like hearing aids, blood pressure sensors, and pace makers, to household appliances, such as washers & dryers, refridgerators, and coffee makers, to automotive, industrial and aerospace applications.

Components of a computer

There are 5 types of components in a computer system:

• CPU (Brain)
• oscillator (crystal, RC oscillator or any other clock source), used to clock the CPU
• Program memory (ROM), Non volatile memory containing a list of instructions to execute sequentially by the CPU
• RAM (read/write memory. Typically volatile, so losing content at power down)
• Output units
• Input units

Of these 6 types, only the first three are actually required for a functioning computer. This computer will simply fetch instructions from program memory and execute them sequentially. Unfortunately, a computer consisting of no more than that will be completely useless, as it has not way to communicate with the outside world. In other words: Whatever this basic computer does is completely irrelevant, as it can not be see by anyone and has no effect on the world at all. The next thing it needs is an Output unit. Now we can start to build a computer that can actually be used for some things. The uses are still very limited, as it does not have input and memory, but still some things can be done, such as a clock (showing up time since power up) or a timer that beeps after a certain period of time, such as an egg timer. Adding inputs (such one or more buttons to adjust or reset the time) can make it more valueable. There can also be other inputs, such as a analog inputs, that have to go through an ADC (Analog to Digital Converter), to measure things such as temperature. Adding RAM might be important when the little bit of short term memory in the CPU (The CU registers) are no longer sufficient to get the job done.