Bits, Bytes, Speed & Size

At their most basic level, computers communicate in binary language. Binary can be thought of as a series of switches that can either be "on" or "off", representing the presence or absence of electricity. Everything done with computers is converted into binary since they run on electricity. These two positions are represented by the computer as 1s and 0s. Practically all electronic equipment uses 1s and 0s on their power switches, so this convention should be familiar. 1 is ON and 0 is OFF.

Button    Switch

Digital information is made up of discrete countable units, so it can be subdivided exactly, as opposed to analog information, which continuously varies over a range of values. The following pictures are camouflage in analog and digital patterns. The colors on the first picture look smooth, whereas the colors on the second picture are small squares. If the blocks are small enough or if you stand far enough back, the digital pattern looks continuous, even if it is not. Computers store and process information in a digital format, but humans process and store analog information.

smooth    blocks

Computers are found in many electronic devices and machinery, such as cars, DVD players, traffic lights, etc. These are called embedded computers, since they are embedded in another device to add specific functionality. They are usually less powerful than the desktop PC you usually use, since they are designed for a more limited purpose.

Size

Whatever the type of computer, the smallest unit of storage is a binary digit or bit. A bit can only store a single 0 or 1 and does not convey much information by itself. A string of 8 bits is called a byte, and with its 256 possible numeric values (2^8=256); it is the unit of data that we use to store one character. Binary is a Base 2 counting system, meaning there are two possible values, 0 or 1, as opposed to how we normally count with a Base 10 counting system, 0 through 9.  The following numbers show a byte (or set of 8 bits) converted to a number, along with the corresponding ASCII text character:

01000001 = "A"
01000010 = "B"
01000011 = "C"

Using the number of bytes to describe storage capacity would be similar to using the number of pennies to describe thousands of dollars... rather cumbersome, to say the least.  The following Latin prefixes help specify the size of the large numbers we use when we talk about computer data file size.

Kilo means thousand.
Mega means million.
Giga means billion.
Tera means trillion.

mnemonic to help you remember the order: Kings Make Great Tyrants

8 Bits ~ 1 Byte

Bytes Kilobytes Megabytes Gigabytes Terabytes
1,000 Bytes 1 KB      
1,000,000 Bytes 1,000 KB 1 MB    
1,000,000,000 Bytes 1,000,000 KB 1,000 MB 1 GB  
1,000,000,000,000 Bytes 1,000,000,000 KB 1,000,000 MB 1,000 GB 1 TB

Most modern hard drives and flash drives will hold many gigabytes of data. A small text file might be just few kilobytes, whereas a picture taken on a 10+ megapixel digital camera might be several megabytes.  A word processing document that has many pages of text and pictures could easily be a couple of megabytes or more. It is important to remember the differences in these terms so that an informative decision can be made, for example, when choosing between a computer with 1 gig of memory and one with 512 megs of memory.  Maybe you need to decide whether to buy the 8 GB USB drive to transport your data files with or if the 1 GB model will do. If more is better, which is more?

Speed

The speed of the Central Processing Unit (CPU) is very important. The faster the CPU, the faster the computer actually runs, since it acts like the brain of the computer. When the speed of a computer is mentioned in an advertisement, that speed references the speed of the CPU.

When we talk about size, we use bytes. When we specify processing speed, we use units called hertz. The number of "hertz" describes the number of electric pulses per second, and the same prefixes are used with hertz as is used in bytes to specify larger values.

Currently, the speed of CPU's are measured in megahertz or gigahertz; most new computers will run anywhere from 1.5 to about 3.8GHz. A computer that runs at 800 megahertz has a CPU that can issue 800 million pulses per second, whereas a CPU that runs at 3.2 GHz can issue 3.2 billion pulses per second. 3.2 GHz is about 4 times faster than 800 MHz. Many new computers now come with two or even more processors, which greatly improves performance by allowing the computer to process more information at the same time.

Smaller devices such as phones and PDAs will run at slower processor speeds, because they don't have the power to run that fast or the cooling system to handle the extra heat.  That is the same reason a laptop will generally not be as fast as a regular desktop computer. A server or mainframe will be physically larger than a desktop computer because it will have more processors and a stronger power and cooling system. They are often put in special server rooms with backup power and cooling to keep the system running.  A supercomputer is generally a set of servers that are hooked together to run even faster in order to calculate large scale problems like predicting the weather, breaking encryption, mapping genomes and other biology or physics projects, and tracking the contents of the Internet for search engines.

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