1. Chapter 2 In Brief…

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

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

4. Technology Name D/L Speed Cons Modem 56 Kbps Very Slow ISDN 128 Kbps Expensive DSL 1.5-8.4 Mbps Avail., Sym., Dist. T1 Line 1.5 Mbps Expensive Cable Modem 10 Mbps Saturation, Sym. T3 Line 45 Mbps Expensive http://pirate.shu.edu/~hoffmake/Bandwidth_cht.html

5. SPAM Don’t open it Don’t answer it Discourage your friends from doing so Filter it if possible Never send UCE! Unsolicited Commercial Email SPAM at IU? http://kb.iu.edu/data/alfb.html http://kb.iu.edu/data/alfb.html

6. 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

7. Hardware – The System Unit

8. 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).

9. 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.

10. 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. "10011101010"). Information as the computer knows it is bit strings: strings of bits (e.g. "10011101010"). 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.

11. Hardware The rest of the lecture is found at the following web page: http://www.cs.indiana.edu/classes/a111/lecture2.html We’ll be covering this material over the next few lectures