Module 1: Using Computers, LANs, and Email for Academic Coursework

Bits, Bytes and Megahertz

Computers are often defined by numbers. To understand a computer and the importance of some crucial computer components, you must learn what some of these numbers mean.

The "bit" is the basic unit of computer memory. It represents one of the two possible states--on or off--also known as 0 and 1 or binary notation. This is how a computer understands its world. Everything a computer does is based on 0 or 1 and each 0 or 1 is a binary digit or bit. Bits are grouped into eight digit codes called bytes. The American Standard Code for Information Interchange (ASCII) sets the standard system for the binary representation of characters. Thus, each key on a keyboard has its own eight bit (1 Byte) representation. For example, the letter A is 01000001 and the letter B is 01000011. The computer doesn't manipulate data in terms of "letters" but in sequences of bits and bytes. It does this at incredible speeds.

Figure 1: Binary versus Digital Systems

Source: Bandwidth place (http://bandwidthplace.com/tech/?v=bits)

The amount of data contained in computers nowadays requires sizes in the billions. We commonly use terms such as kilobytes (KB), megabytes (MB), gigabytes (GB) and terabytes (TB) to represent these sizes. A kilobyte is 1024 bytes (210), while a megabyte is 1024 kilobytes, a gigabyte is 1024 megabytes and a terabyte is 1024 gigabytes.

RAM sizes are normally measured in megabytes. RAM comes in chip sizes of 32, 64, 128, 256 and 512 megabytes. Hard disk drives come in a wide variety of sizes. The most common now are 40, 60, 80, 120 and 160 GB. Floppy disk drives hold 1.44 megabytes of data. CDRom drives commonly hold about 700 megabytes of data. DVD drives hold up to 3.7 gigabytes of data.

The CPU processing power is normally measured in megahertz or gigahertz (MHz or GHz). This is measured in terms of the cycles that the processor performs per second. Intel Pentium microprocessors now are commonly clocked at 2 to 3Ghz. This speed enables the computer to process data extremely quickly.

The speed of the internet is measured according to the ability to send and receive information. This depends on type of internet connection you are using. A dial-up connection to the internet using a modem is normally carried out with 56KB modem. This means that the connection is capable of transferring 56000 bits per second. In practice the connection may be a lot slower. Network connections (e.g Ethernet) are measured in bandwidth, again the ability to transfer data. It is important to note that communication speeds are usually measured in bits per second while most other computer operations are measured in bytes per second. The larger the bandwidth the faster information can be transferred. Common bandwidth sizes are 128 MB, 256 MB, 512 MB. Another common wideband system is Digital Subscriber Line (DSL). These systems can transfer data at rates up to 8 M bits per second.

These numbers are important to the user as the speed and the functionality of the computer is related to the size of RAM, Hard disk drive, and processor speed (among other things). If you are working with the internet, the raw power of the computer is secondary to the speed of the internet connection. Thus, the computer user must be concerned about the size and speed of each of the components of the machine. Larger numbers usually reflect a more powerful machine. However, larger numbers also reflect a higher price.