3.2. Digital Devices
A digital device processes electronic signals into discrete values, of which there can be two or more. In comparison analog signals are continuous and can be represented by a smooth wave pattern. You might think of digital (discrete) as being the opposite of analog.
Many electronic devices process signals into two discrete values, typically known as binary. These values are represented as either a one (“on”) or a zero (“off”). It is commonly accepted to refer to the on state as representing the presence of an electronic signal. It then follows that the off state is represented by the absence of an electronic signal. Technically, the voltages in a system are evaluated with high voltages converted into a one or on state and low voltages converted into a zero or off state.
Each one or zero is referred to as a bit (a blending of the two words “binary” and “digit”). A group of eight bits is known as a byte (think of a byte as being a single character you can type from a keyboard). The first personal computers could process 8 bits of data at once. The number of bits that can be processed by a computer’s processor at one time is known as word size. Today’s personal computers can process 64 bits of data at a time which is where the term 64-bit processor comes from. You are most likely using a computer with a 64-bit processor.
As the capacities of digital devices grew, new terms were developed to identify the capacities of processors, memory, and disk storage space. Prefixes were applied to the word byte to represent different orders of magnitude. Since these are digital specifications, the prefixes were originally meant to represent multiples of 1024 (210), this usage is referred to as a binary measurement, but have more recently been rounded for the sake of simplicity to mean multiples of 1000, as shown in the table below.
|kilo||one thousand bytes||1 typewritten page|
|mega||one million bytes||1 digital photo|
|giga||one billion bytes||1 Blu-ray movie 25GB|
|tera||one trillion bytes||Printed Collection of the library of congress 20TB|
|peta||one quadrillion bytes||Data generated on Facebook everyday 4PB|
|exa||one quintillion bytes|
|zetta||one sextillion bytes|
|yotta||one septillion bytes|