Transcript Module 5
Module 5
Hardware
What Computers Do
Process Information Receive Input Store Information Produce Output
4 Primary Components of a Computer
Primary
- memory - RAM - ROM Input Devices Storage Devices Processing
Secondary
- hard disks - removable disks - CDs - tapes Output Devices - keyboard - mouse - scanner - digital camera - touchpad -CPU -Control Unit -Arithmetic & Logic Unit - monitor - printer - speakers
Processing - CPU
“Central Processing Unit” http://www.howstuffworks.com/microprocessor1.htm evolution of processors the “brains” of the computer, where calculations take place two parts: ALU - Arithmetic Logic Unit • electronic circuitry that does all arithmetic and logic operations Control Unit • circuitry that directs all other parts of the computer
Input Devices
accept input from the outside world.
most common is the keyboard , followed by the mouse sends signals to the computer, telling it what you’ve “told” it
Output Devices
sends output to the outside world converts and displays the computer’s internal bit patterns to a format that humans can understand Main output devices are monitors for immediate visual output printers for permanent paper output
Screen Output
A monitor or video display terminal (VDT) displays characters, graphics, photographic images, animation and video.
Video adapter
the computer —connects the monitor to
VRAM
or video memory —a special portion of RAM to hold video images (the more video memory, the more detail of a picture displayed)
Screen Talk
Monitor size
- measured as a diagonal line across the screen.
Pixels
(or picture element) - tiny dots that compose a picture
Resolution
- the number of pixels displayed on the screen (the higher the resolution, the closer together the dots)
Image Quality
Image quality is affected by resolution depth and color (or bit depth) Color depth refers to the number of different colors a monitor displays at the same time
Examples of Color Depth
4-bit depth 1-bit depth 8-bit depth 16-bit depth
Paper Output
Printers produce paper output or hard copy 2 kinds of printers: Impact printers Non-impact printers
Impact Printers
Line printer Used by mainframes to produce massive printouts Limited to printing characters Dot matrix printer Images created by a matrix of tiny dots Low print quality Low cost
Non-impact Printers
Laser Printer
A laser beam reflected off a rotating drum to create patterns of electrical charges Faster and more expensive than dot matrix printer High-resolution output
More on Non-impact Printers
Ink-jet Printer
Sprays ink onto paper to produce printed text and graphic images Prints fewer pages/minute than laser printer High-quality color costing less than laser printer
Storage devices
Storage/Memory Devices
Divided into two groups: Primary storage • usually a temporary storage for the data and programs currently in operation or currently being accessed.
• it’s fastest and most expensive Secondary storage • long-term storage locations • • • cheap but slower than primary memory some are portable/removable larger capacity than primary memory
Primary Storage - RAM
RAM : Random Access Memory very fast - access times < 1 billionth of a second – in nanoseconds volatile storage - once the computer is turned off, everything is lost this is where data and programs currently being used reside a document that has not yet been “saved” is in RAM and will be lost if the computer freezes or the power goes off
Primary Storage - ROM
ROM = Read Only Memory permanent memory (doesn’t disappear if the computer is turned off) normally holds the data/programs needed to start (“boot up”) the computer typically, cannot be altered except by physically changing the chip
RAM ROM
Secondary Storage
Secondary storage devices are computer peripherals capable of performing both input and output functions Information is stored semi-permanently on tape and disk drives Examples of storage devices Magnetic tapes and disks Zip, Jaz and SuperDisks Optical disks
Secondary storage - Magnetic Tape
Magnetic tapes
Sequential access Can store large amounts of information in a small space at a relatively low cost Limitation: sequential access Used mainly for backup purposes
Magnetic Media
Magnetic drives Random access
Floppy disks
storage for inexpensive, portable
Hard disks
are typically non-removable, rigid disks that spin continuously and rapidly thus providing much faster access than a floppy disk.
Removable media
(Zip & Jaz disks) provide high-capacity portable storage.
Hard Disk
magnetic storage data is saved until something is written over it (or it gets damaged somehow) data saved on “platters” and read with a “head” platters spin at 3600-7200RPM head can move to center and back to edge about 50 times per second platters divided into “tracks” and “sectors” to make it easier to retrieve data.
Optical Media
Optical disk drive uses laser beams to read and write bits of information on the disk surface.
Not as fast as magnetic hard disks Massive storage capacity and reliability
Types of Optical Media
CD-ROM
drives are optical drives that
read
CD-ROMs.
CD-R
are
WORM
media (write-once, read many). Hold about 700megabytes of info
CD-RW
can read CD-ROMs and write (onto CD-R), erase and rewrite data onto CD-RW disks.
DVD
(digital video disks) store & distribute all kinds of data. They hold between 3.8 and 17 gigabytes of information.
Solid-state Storage Devices
Flash memory is an erasable memory chip.
Compact alternative No moving parts Designed for specific applications such as storing pictures in digital cameras Likely to eventually replace disk and tape storage
Processing
The CPU
The microprocessor that makes up your personal computer ’ s
central processing unit
, or CPU , is the ultimate computer brain, messenger, ringmaster and boss. All the other components — RAM, disk drives, the monitor — exist only to bridge the gap between you and the processor.
Ron White, in How Computers Work
The CPU
The CPU:
interprets and executes instructions performs arithmetic and logical data manipulations communicates with the other parts of the computer system.
The CPU
The CPU is a complex collection of electronic circuits.
When all of those circuits are built into a single silicon chip, the chip is referred to as a
microprocessor
.
The circuit board that contains a computer’s CPU is called the
motherboard
or
system board
.
motherboard CPU
CPU Speed
A computer’s speed is determined in part by the speed of its internal clock
The clock is a timing device that produces electrical pulses to synchronize the computer’s operations. A computer’s clock speed is measured in units called megahertz (MHz), for millions of clock cycles per second
CPU Speed
Parallel processing
places multiple processors in a computer.
Most supercomputers have multiple processors that divide jobs into pieces and work in parallel on the pieces.
Ports and Slots
Tying things together
Ports and Slots
The system or motherboard includes several standard ports:
Serial Port
for attaching devices that send/receive messages one bit at a time (modems)
Parallel Port
for attaching devices that send/receive bits in groups (printers)
Keyboard/Mouse Port
and a mouse for attaching a keyboard
More on Ports and Slots
Other ports are typically included on expansion boards rather than the system board:
Video Port
used to plug in a color monitor into the video board
Microphone, speaker, headphone, MIDI ports
used to attach sound equipment
SCSI port
allows several peripherals to be strung together and attached to a single port
Expansion Made Easy
With the open architecture of the PC and the introduction of new interfaces, you can now hot swap devices.
USB (Universal Serial Bus) transmits a hundred times faster than a PC serial port Firewire (IEEE 1394) can move data between devices at 400 or more megabits per second high speed makes it ideal for data-intensive work like digital video
Bits and Bytes
Information
Information comes in many forms Text Pictures 2 1 3 Numbers Sounds Computers store information in digital form
Bit Basics
On/off A bit (binary digit) is the smallest unit of information can have two values:
1
or
0
can represent
numbers, codes,
or
instructions
Bits as Numbers
Each switch can be used to store a tiny amount of information, such as: An answer to a yes/no question A signal to turn on a light Larger chunks of information are stored by grouping bits as units 8 bits (byte) = 256 different messages
Bits As Codes
ASCII
– American Standard Code for Information Interchange Most widely used code, represents each character as a unique 8-bit code.
Bits as Instruction
The computer stores instructions as collections of bits. For instance, 01101010 might instruct the computer to add two numbers.
Other bit instructions might include where to find numbers stored in memory or where to store them.
Bits, Bytes, and Buzzwords
Terms used to describe file size or memory size: Byte Kilobyte (KB) Megabytes (MB) Gigabytes (GB) Terabytes (TB) = 8 bits ≈ 1 Thousand Bytes ≈ 1 Million Bytes ≈ 1 Billion Bytes ≈ 1 Trillion Bytes
The logic machine
How do we build a computer that doesn’t need to be rewired each time we want to perform a different task?
Connect the components in such a way that the program itself controls the “rewiring” by signaling the hardware to switch the components on and off in the proper sequence
Logic Gates
Using switches, we can reproduce the logical operators AND OR NOT 0 = false = off 1 = true = on
AND
P
0 0 1 1
Q
0 1 0 1
PQ 0 0 0 1
AND is written like a multiply
OR
P
0 0 1 1
Q
0 1 0 1
P+Q 0 1 1 1
OR is written like an addition
NOT
P
0 1
P’ 1 0
NOT is written with an ’ after the letter
Simple Truth Table
P
0 0 1 1 0 1 0 1
Q PQ + P’Q’ (result)
1 0 0 1 “if both P and Q are the same, then the result is true”
Example: check to see if P and Q are equal Step 1: build Truth Table The truth table for “P and Q are equal” looks like:
P 0
0 1
1 Q 0
1 0
1 Result 1 0 0 1
P = 0, Q = 0 they are equal so result is true (1) P = 1, Q = 1 they are equal, so result is true (1)
Step 2:
Build an AND statement for each line where Result = 1
P 0 1 Q 0 1 Result 1 1
the ’ means NOT… so P’ means that P is off/0 P’ AND Q’ = P’Q’ P AND Q = PQ
Step 3:
Join each line with OR-statements P’Q’
OR
PQ
result = P’Q’ + PQ
Example 2:
Step 1: Build Truth Table … already done for us
P Q S
0 0
1 P’Q’
0 1
0
1 1 0 1
1 1 PQ’ PQ
Step 2: Build equation terms using ANDs
P
0 0 1 1
Q
0 1 0 1
S 1 0 1 1 P’Q’ PQ’ PQ
Step 3: Build equation by joining terms from step 2 with ORs
S = P’Q’ + PQ’ + PQ
Drawing circuits
AND = OR = NOT = *
Gates
Two inputs = Two inputs + = One input ’ = One output One output One output
Gates to switches
Logical gates can be converted to physical switches that operate exactly as expected We can combine gates to act like our statements from the truth tables since we have a gate for each of AND, OR, NOT
Building Circuits
We build the circuit in the exact same order as we build the equation figure out the inputs do all the NOTs next all the ANDS lastly all the ORs
Result = PQ + P’Q’
Example
Step A: Inputs P Q One input (light switch) for each letter in the equation
Step B: NOTs Result = PQ + P’Q’ P
P
Q
Q P’ Q’
Result = PQ + P’Q’ Step C: ANDs P Q
P Q P’ Q’ PQ P’Q’
Remember AND is the same as a multiply
Step D: ORs Result = PQ + P’Q’ P Q Remember OR is the same as addition
PQ P’Q’ PQ + P’Q’
The light will light up when the inputs are both the same, as described in the truth table
Example
3 inputs, light-up if exactly 2 inputs are true Step 1: Build Truth Table
X
0 0 0 0 1 1 1 1
Y
0 0 1 1 0 0 1 1
Z
0 1 0 1 0 1 0 1
Result 0 0 0 1 0 1 1 0
Step 2: build terms with ANDs (where result is true)
X
0
Y
0
Z
0
Result 0
0 0 0 1 1 0
0 0
0 1 1 0 1 0
1 0
X’YZ 1 1 0 1 1 0
1 1
XY’Z XYZ’ 1 1 1
0
Step 3: Build equation by joining terms with ORs result = X’YZ + XY’Z + XYZ’
Step 4: Build circuit result = X’YZ + XY’Z + XYZ’ Step A: Inputs X Y Z
Step B: NOTs result = X’YZ + XY’Z + XYZ’ X X’ Y Y’ Z Z’
Step C: ANDs result = X’YZ + XY’Z + XYZ’ X X’ Y X’Y Z X’YZ Y Y’ X Z Y X XY’ Z Z’ XY XY’Z XYZ’
X Y Z result = X’YZ + XY’Z + XYZ’
X’YZ XY’Z XYZ’
X Y Z result = X’YZ + XY’Z + XYZ’ X’YZ
X’YZ + XY’Z
XY’Z XYZ’
X’YZ + XY’Z+ XYZ’
Using Loggo to combine gates
Go to the class homepage and look for the
Loggo
applet in the Miscellaneous section Try implementing different equations to see if they match the truth tables
Corresponding Readings
Chapter 2 Chapter 3
To Know – Module 5
Vocabulary/definitions Truth tables / circuits From a description, write truth table From truth table, write equation From equation, build circuit