************ This is some followup to class two (January 10th) ************ Note: It is NOT expected you understand the binary until the end of week #2 or #3. The textbook CD-ROM has a very easy to understand lab that goes with binary and chapter two that will be assigned on Friday, January 12th and not due until the 22nd of January, which is the Monday one week from the Martin Luther King holiday. A byte consists of 8 bits. The electronic digital computer uses two digits, since electricity is most easily engineered to either be off or on. For example, a light switch can be off, represented by 0, or can be on, represented by 1. Current can be flowing or not flowing, switches and bulbs can be on or off, voltage can be high or low. Bits is an abbreviation for binary digits. Binary digits = bits. -- -- -- -- ---- With one bit, with one light switch, you can represent two things. 0 off Vanilla 1 on Chocolate With two bits, you can represent four things. 00 Vanilla 01 Chocolate 10 Strawberry 11 Jamoca Almond Fudge Similarly, 3 bits can be used to represent 8 things. 000 = 0 100 = 4 001 = 1 101 = 5 010 = 2 110 = 6 011 = 3 111 = 7 With 4 bits, you can express 16 different things, from 0000 = 0 ... thru 0111 = 7 and 1000 = 8 ... and finally to 1111 = 15 4 bits is called a nybble, in case we need a name for half of a byte. 8 bits is a byte, so 2 nybbles = 1 byte Ms is secondary storage or secondary Memory. -- - - - - Hard drives, diskettes, flash drives are common examples of Ms. Ms storage is non-volatile. It is usually magnetic. Non-volatile means it is more or less permanent, or semi-permanent. You can save your work to the hard drive of your computer, before you turn it off, and come back the next day and it is still there. Mp stands for primary Memory. Mp is also often called main memory, - - or RAM. Mp is volatile. Mp is much more expen$ive than Ms for storing information and data. Volatile means if there is power surge or spike, or if the computer gets turned off, all the information in electronic, volatile RAM is lost. It evaporates. It is a temporary and not a permanent place to keep data. Why do we have to have data in volatile RAM, in volatile Mp? Because that is the computer's desktop. The CPU cannot operate on data or execute the instructions of a program unless the data and the program are placed on its desktop (RAM or Mp). The file cabinet or desk drawer or backpack of the computer is the Ms, the secondary memory or auxilary memory or storage. We talked about the Input and Output and Bus components to round our our discussion of the 6 essential hardware components of any computer. CPU Mp Ms Output Input -------------------------------------- the bus -------------------------------------- You have this all laid out very nicely on the January 8th handout. We talked about the amounts of memory that are typical for Mp and for Ms. Here is a www.dell.com computer's specs for Mp and Ms. 512 MB Single Challel DDR2 simply means it has 512 MegaBytes (MB) of primary memory or RAM. 80 GB Serial ATA Hard Drive means it has an 80 Gigabyte hard drive. 512 MB of Mp is the same as 1/2 GB of Mp. A diskette holds 1.44 MB, which is the same as 1440 KB. 1 kilobyte = 1 KB = 1024 bytes. 2 1 megabyte = 1 MB = 1024 KB = 1024 = about 1 million. 3 1 gigabyte = 1 GB = 1024 MB = 1024 = about 1 billion. # of bits # of things that can be represented 1 2 3 4 5 6 7 8 256 8 bits = 1 byte (size of 1 byte) 9 512 10 1024 1024 = 1KB = 1 kilobyte = number of bytes in 1 KB 11 2048 = 2KB 12 4096 = 4KB 13 8KB 14 16KB 15 32KB 16 64KB 17 128KB 18 256KB 19 512KB 20 1024KB = 1 MB = number of bytes in 1 MB, or one megabyte, about one million. 21 2 MB 22 4 MB 23 8 MB 24 16 MB ... 29 512 MB 30 1024 MB = 1 GB = one gigabyte or about 1 billion bytes. See you in Wright Hall 112 lab on Friday January 12th. Hands-on computer lab class in Wright 112 on 1/12. Very poetic! :-) Mark