Computer

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

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, refrigerators, and coffee makers, to automotive, industrial and aerospace applications.

Components of a computer

There are 6 types of components in a computer system:

1. CPU - The Brain.
2. Clock generator. It is used to supply the clock to the CPU, or to "clock" it.
3. Program Memory. It contains the instructions to be executed sequentially by the CPU. Since these instructions need to be there after Reset, this is typically a ROM.
4. Output Unit. Sends data out. In a simple case, it is binary, so it can switch a light, LED or motor on/off.
5. Input Unit. Reads data from the outside. In a simple case, this is just a switch or push button.
6. RAM. Read/write memory used to hold data. It is typically volatile, so its content is lost when the computer is powered down.

Essential components

The first three components are absolutely essential for a computer to function. With these components, the Clock will prompt the Brain to keep fetching instructions from the ROM and to keep executing them sequentially. This is all it takes! Unfortunately, such a computer has no way to communicate. The results of its executed instructions cannot be seen by anyone and thus whatever it does is irrelevant to the outside world. In other words: It is a computer, but it is completely useless.

Adding Output

By adding an Output Unit we start to see a computer with some limited uses. It be used as a clock that displays the amount of time since powering up (but that resets when powered down) or it can serve as a timer that beeps after a certain period, like an egg timer.

Adding Input

Next we add an Input Unit. A simple addition is a button. In the above example the button resets the clock or timer. Other input devices measure things such as temperature.

Adding RAM

As the complexity of the task increases, the short term memory in the CPU (the CPU register) will no longer be sufficient to get the job done. Adding the sixth type of component, RAM, greatly increases functionality and completes the build-out of our basic computer system.