Chapter 2 In Brief…

Chapter 2 …Is a little boring. Sorry. But it contains material you need to be familiar with

Terms Bandwidth - how much you can send through a connection Bps - bits per second Kbps bps Mbps Kbps Gbps – 1000 Mbps

Technology Name D/L Speed Cons Modem 56 Kbps Very Slow ISDN 128 Kbps Expensive DSL Mbps Avail., Sym., Dist. T1 Line 1.5 Mbps Expensive Cable Modem 10 Mbps Saturation, Sym. T3 Line 45 Mbps Expensive

SPAM Don’t open it Don’t answer it Discourage your friends from doing so Filter it if possible Never send UCE! Unsolicited Commercial SPAM at IU?

The rest of CH 2 Is mostly basic, so we’re not going to cover it in lecture However, you will be expected to be familiar with any terms and ideas introduced in it

Hardware – The System Unit

Representing Information A Bit: the unit of information in a computer. Computers "process" electric currents (electrical events). Computers "process" electric currents (electrical events). The current is either "on" (=1) or "off" (=0) in a particular circuit at a particular time. The current is either "on" (=1) or "off" (=0) in a particular circuit at a particular time. This gives rise to the binary system for storing information. This gives rise to the binary system for storing information. Each transistor in a computer's memory can hold one bit of information (either a 0 or a 1). Each transistor in a computer's memory can hold one bit of information (either a 0 or a 1).

Representing Information Basic Measures for Information Capacity The information capacity of a storage deviced is measured in multiples of bits. The information capacity of a storage deviced is measured in multiples of bits. Bit: 0 or 1. Bit: 0 or 1. Byte: 8 bits. Can represent one of 2^8 = 256 numbers. Byte: 8 bits. Can represent one of 2^8 = 256 numbers. Kilobyte: Kilo (thousand) + byte: 2^10 bytes = 1,024 bytes. Kilobyte: Kilo (thousand) + byte: 2^10 bytes = 1,024 bytes. Megabyte: Mega (million) + byte: 2^20 bytes = roughly a million bytes. Megabyte: Mega (million) + byte: 2^20 bytes = roughly a million bytes. Gigabyte: Giga (billion) + byte: 2^30 bytes = roughly a billion bytes. Gigabyte: Giga (billion) + byte: 2^30 bytes = roughly a billion bytes. Terabyte: Tera (trillion) + byte: 2^40 bytes = roughly a trillion bytes. Terabyte: Tera (trillion) + byte: 2^40 bytes = roughly a trillion bytes. Petabyte: Peta (quadrillion) + byte: 2^50 bytes = roughly a quadrillion bytes = 1,000,000,000,000,000 bytes. Petabyte: Peta (quadrillion) + byte: 2^50 bytes = roughly a quadrillion bytes = 1,000,000,000,000,000 bytes.

Representing Information Information Information as we think of it is data with meaning: text, pictures, sounds. Information as we think of it is data with meaning: text, pictures, sounds. Information as the computer knows it is bit strings: strings of bits (e.g. " "). Information as the computer knows it is bit strings: strings of bits (e.g. " "). Information as we know it is encoded in a computer using bit strings. Information as we know it is encoded in a computer using bit strings. An encoding is an agreed-upon standard that dictates the specifics of how the information is represented using 0s and 1s. An encoding is an agreed-upon standard that dictates the specifics of how the information is represented using 0s and 1s. Example: ASCII is a widely-used text encoding standard. Under this encoding, each letter & digit & punctuation mark is assigned an 8-bit code which represents it. (How many possible such codes are there?) Example: ASCII is a widely-used text encoding standard. Under this encoding, each letter & digit & punctuation mark is assigned an 8-bit code which represents it. (How many possible such codes are there?) Newer (more comprehensive) standard for text encoding: UNICODE. Newer (more comprehensive) standard for text encoding: UNICODE.

Hardware The rest of the lecture is found at the following web page: We’ll be covering this material over the next few lectures