Today’s Topics  Chapter 6: System Unit  Chapter 7: Input/Output and Storage

Chapter 6 System Unit

How Computers Represent Data  Bit (Binary Digit): smallest unit of information that a computer can work with (0 or 1)  Kilobits Per Second (Kbps) = 125 characters  Megabits Per Second (Mbps) = 125 pages  Gigabits Per Second (Gbps) = 125,000 pages  Byte: one unit of storage consisting of 8 bits  Kilobyte (K or KB) = 1 page  Megabyte (M or MB) = 1,000 pages  Gigabyte (G or GB) = 1,000 books  Terabyte (T or TB) = 1 million books

Decimal Number System  6 = (6 x 10^0)  45 = (4 x 10^1) + (5 x 10^0) =  214 = (2 x 10^2) + (1 x 10^1) + (4 x 10^0) =

Binary to Decimal Conversion  0 = (0 x 2^0) = 0  1 = (1 x 2^0) = 1  10 = (1 x 2^1) + (0 x 2^0) = = 2  11 = (1 x 2^1) + (1 x 2^0) = = 3 (1 x 2^1) + (1 x 2^0) = = 3  = (1 x 2^5) + (0 x 2^4) + (1 x 2^3) + (0 x 2^2) + (1 x 2^1) + (1 x 2^0) = = 43 (1 x 2^5) + (0 x 2^4) + (1 x 2^3) + (0 x 2^2) + (1 x 2^1) + (1 x 2^0) = = 43

Decimal to Binary Conversion  2^7 2^6 2^5 2^4 2^3 2^2 2^1 2^0 =   To convert a decimal number to binary, first subtract the largest possible power of two, and keep subtracting the next largest possible power from the remainder, marking 1s in each position where this is possible and 0s where it is not.

Decimal to Binary Conversion  2^7 2^6 2^5 2^4 2^3 2^2 2^1 2^0 =  =   = 23  = 7  = 3  = 1  = 0

Character Code  American Standard Code for Information Interchange (ASCII): used for the Internet  Extended Binary Coded Decimal Interchange Code (EBCDIC): used on IBM mainframe  Unicode: represents many foreign languages

CPU Subcomponents  Control Unit: extracts instructions from memory and decodes and executes them  Machine Cycle or Processing Cycle  Instruction Cycle  Fetch: retrieves the next program instruction from memory  Decode: determines what the program is telling the computer to do  Execution Cycle  Execute: performs the requested instruction  Store: stores the results to an register or memory  Registers: Temporary Storage Locations in CPU  Arithmetic-Logic Unit

CPU Performance  Data Bus: highway of parallel wires connecting CPU internal components  Word Size: maximum number of bits the CPU can process at once  System Clock: electronic circuit that generates pulses at a rapid rate and synchronizes the computer’s internal activities (GHz)

Techniques to Improve CPU Performance  Superscalar Architecture: design of CPU that can execute more than one instruction per clock cycle  Pipelining: processing technique that feeds a new Instruction into CPU at every step of processing cycle  Data Dependency: result of a completed instruction to process the next one

Techniques to Improve CPU Performance  Speculative Execution: processor executes and temporarily stores the next instruction in case it proves useful  Branch Prediction: processor tries to predict what will likely happen Example: IF A = B THEN Example: IF A = B THEN C = C + 1 C = C + 1 ELSE ELSE C = C - 1 C = C - 1 END IF END IF

Techniques to Improve CPU Performance  Parallel Processing: technique that uses more than one processor running simultaneously

Memory  Memory: chips that enable the computer to retain information  Random Access Memory (RAM): stores information temporarily  Read-Only Memory (ROM): prerecords instructions to start the computer and cannot be erased  Cache Memory: stores frequently or recently accessed program instructions and data

Chapter 7 Input/ Output and Storage

Input Devices  Keyboard  Insertion Point: the location of the cursor that shows where text will appear when you type  Toggle Key: the key that has only two positions which are on and off  Example: Caps Lock Key  Function Keys: keys that provide different commands, depending on the program in use  s/article894.htm s/article894.htm s/article894.htm

Input Devices  Keyboard  Modifier Keys: the keys that have no effect unless holding them down and pressing a second key  Ctrl + A  Ctrl + X  Ctrl + C  Ctrl + V  Ctrl + Home  Ctrl + End  Window + D

Input Devices  Mouse  Trackball  Pointing Stick  Touch Pad (Track Pad)  Joystrick  Touch Screen  Light Pen  Stylus  Microphone  Scanner  Bar Code Reader

Output Devices  Monitor  Liquid Crystal Display (LCD) / Flat-Panel Display  High Definition Television (HDTV)  Screen Size  Resolution: sharpness of an image  Refresh Rate: frequency at which the screen image is updated in Hz

Output Devices  Printer  Inkjet Printer (Bubble-Jet Printer)  Laser Printer  Plotter  Projector

Storage  RAM VS Storage  Storage devices are non-volatile: retaining data when the current is switched off  Storage devices are cheaper than memory  Storage devices are important in system startup operations  Storage devices are needed for output

Storage  Hard Disk Drive  File Allocation Table (FAT): table that keeps track the location of files in MS Windows  Partition: section of a disk enabling computers to work with more than one OS  Internet Hard Drive: storage space on a server that is accessible from the Internet

Storage  Floppy Disk: 1.44 MB  Zip Disk: 750 MB  CD-ROM/ CD-R/ CD-RW: 650 MB  DVD-ROM/ DVD-R/ DVD-RW: 17 GB  FMD-ROM: 1 TB  Solid-State Storage Devices  PC Card (PCMCIA)  Flash Memory Card  Smart Card