Machine Level Architecture

What are the basic internal components of a computer system?

The  basic internal components of a computer system is the: Proccessor, Main memory, the I/O and the bus which connects them together. This is known as the CPU (Central proccessing unit).

3-Box model:

Proccessor
The proccessor is the component which runs programs and looks after other components

Main memory
This is also known as the immidiate access store (IAS). this components is used to store instructions and data. This is made up of RAM and ROM.

RAM (Random Access Memory): This only holds quick access data/instruction, and only when the computer is turned on.

ROM (Read-only Memory: This is used to store programs needed to start the computer (bootstraping)

I/O
Everything that isn't in the CPU is a peripheral.

I/O controller: allows the computer to communicate with peripherals without the CPU knowing how they work.

I/O Ports: its a method of performing inputs and outputs between CPU and peripheral devices in a computer.

Bus
aka system bus or external bus. It connects the other components and is made up of several parallel wires.
There are 3 bus' the:

Address bus
A single direction bus that sends address' to the components of the three box model.
Data bus
This carries control signals between the 3-Box model.

Control bus
This carries commands from the CPU and sends back status from the other devices.

Logic gates

Image from:

 http://www.curriculum.org/csc/library/profiles/10/html/TEE2OP2_files/image002.gif

Hardware Devices

Input

• Mouse- This works using either a laser which the ray gets broken(shortened) as it is moved across a surface. Or, a ball mouse which as it is rolled across a surface it hits a switch at either side of the mouse.
• Voice reconition- This works by recording the input and relating it to a command (compares it)
• Graphics tablet-This works as it has small sensors throughout it which when pressed on pickup how hard the pen is pushed onto, thus making so that different pressures can be pcked up.
• Keyboard-A key board worksas it has metal contacts under the plastic keys that when pressed together complete a circuit letting the computer know what button has been pressed.
• Touch-sensitive screen- This works by putting a feild of lasers across the screen. When these are broken by a finger/object it lets the hardware know where it is being pressed.
• Digital Still/video camera

Readers:
Magnetic

• Magnetic stripe reader-The card has magnetic parts which when swiped are picked up as 0's and 1's
•  Smart card reader-has a chip that is read by the smart card reader. this small chipcan store small amounts of information and even small software.

Optical

• Bar code reader-the bar code reader reflects lasers off the strip(white reflects the laser back better) and thee are picked up as 1's and 0's
• Optical mark reader-LIke the bar code reader this uses lasers that reflect lighter parts back and black parts not as much, where these are on the page corespond to where the light from the laser doesn't return.
• Optical character recognition- This captures the characters on the object and compares them in its database of character(this is to reconise them) and then they are pasted.

Radio

• Radio frequency identification reader-This uses exlectro magnetic waves(radio signals) and sends them out from where ever it is so that it can be located (this would normaly be placed on an object like a bag at an airport so that it could be easily located/allocated.

Scanner

• Fingerprint scanner-This uses a light that reflects nicks and bumps in the skin back to the machine giving it an image that can be used to identify someone.
• Retina/Iris scanner-This uses a very weak laser which is shone into the eye of the person and picks out unique characteristics from the retina/iris. this can then be used to identify people.
• Flatbed scanner- A light is shone onto the object in the scanner which is reflected back as an image  and picked up by a sensor. CCD-type scanners typically contain three rows (arrays) of sensors with red, green, and blue filters.

Output Devices:
Displays

• Cathode ray tube (CRT)- This works with a vacuum tube containing electrons and a fluorescent screen. These are used to create the image on the screen (The light emitted from the fluorescent screen) 
• Plasma screen- This works as he xenon and neon gas in a plasma television. This heats up the magnesium oxide which in turn goes through colour panels, the back of each cell is coated with a phosphor. The ultraviolet photons emitted by the plasma excite these phosphors to give off coloured light(this is what we see)
• Flat screen (Liquid crystal display LCD)-This works by using the light modulating properties of liquid crystals. These are lit up with blue green and red LED's.

Printers 

• Inkjet printer- These spray ink onto the paper (droplets)
• Laser printer-These work by using using dry ink (toner), static electricity, and heat to place and bond the ink onto the paper. The paper is rolled over a drum as this happens
• Impact(dotmatrix) printer-a series of small pins to strike a ribbon coated with ink, causing the ink to transfer to the paper at the point of impact.
• Plotter-A plotter is a graphics printer that uses a pen or pencil to draw images. Plotters differ from printers in that plotters use continuous lines to create images while printers use a collection of dots.
  

Sound/Speech Output-Speakers turn electrical signals into Sound. A Microphone turns sound into electrical signals

Different types of software

Hardware:

• This being the physical components of a computer.

Software:

• This being the programs or applications that send information or commands to the hardware.

System                                                                              

• Operating System, Things like windows or Mac that would well operate the system
• Library Programs, These provide functions commonly used by other software e.g. printing routines
• Utility Programs,  These are things like anti-virus that help the system and perform specific tasks.
• Translators, These translate machine code to things that you would use in VB (assembly code) or vice versa
• Assembler, Assembly to machine code 
• Compiler,  Compiles higher level language into machine code. This is done whole source which takes ages but only needs to be done once and end user doesn't need anything to run it.
• Interpreter, Analyses and executes line by line.Pros: can be used straight away cons: runs slow because its analysing all the time.

Application

• General, Software which can be used for many tasks like a spreadsheet e.g. excel(often bought off shop shelf)
• Special, This is software made for 1 purpose e.g. accounting software
• Bespoke, Software written by request for a certain customer.Pros: does exactly what asked for with contract cons: costly.

Generations of software

• 1st gen, Machine code, 0's and 1's
• 2nd gen, Assembly, uses human mnemonics next to machine code (making it easier to read)
• 3rd gen, Imperative High Level, a statement that needs to be compiled into several machine code statements e.g. VB
• 4th gen, Declarative, this is what you want the computer to compute  e.g. SQL

 

yet another innovation: 360 Autostereoscopic Display (Hologram)

Sometime this month in the United States the 'RayModeler' will be Shown at Siggraph 2010 at the Los Angeles Convention Center July 25-29.  Can you imagine how this kind of 3D technology will become part of our everyday lives.

This might not be quite the hologram projection in Star Wars, but it is getting in that direction. Anyone want to try guess how much it's gonna cost (I don't know)


here's a nice video I found of this in use : http://www.youtube.com/watch?v=_Lf0t6gWLB0

Web page design

What is HTML?
Hypertext mark-up language is a "computer language" used to structure web pages.


What are the tags you need to know for the exam? 
HTML uses tags to structure a webpage. For the exam you will need to know these tags:
<html> = beginning of a html page
<head> = the heading and title of a page
<body> = the main body of text of a page
<em> = italic
<strong> = bold
 <p> = paragraph
<hr> = horizontal line across the page
<br> = break in the text
<a href> = hyperlink
<img> = image






What is CSS? 
Cascading Style Sheets. This is used to style web pages. CSS is different to HTML as it separates document content  from document presentation, including elements such as the layout, colours, and fonts.
CSS is split up using selectors e.g.
p {color : Blue;}

The Structure of the Internet

The internet is a Global network of networks that all overlap each other like a mesh. This is so that if we lose a few links it wont cause a big problem.

Information is moved around the internet via packets. These packets contain key things:  the sender's IP address the receiver's IP address and a number that tells the sequence that it goes in.

The Intranet is a small network intended for a company or school. It can host private websites and can be used for communication within the company.

The Extranet is a network that allows controlled access from the outside of a specific business. It's like an extension of the Intranet.

Information on the internet is addressed as an IP address (Internet Protocol address) this is a numerical label specific to a certain network. It would look a bit like this:  208.77.188.166

Computers have domain names which are labels for IP addresses (human readable). A DNS (Domain name server) would translate domain names into IP addresses. An Internet registrar allocates a block of ip addresses to a certain region of the world.

A client-server model:

The most common model for distributing a system is the client-server model. The model is fairly simple to explain and use. 
The name of the model is quite descriptive. In your distributed system you have one or more servers. These servers provide services to other parts of the system, called clients. When a server is started it first opens up a particular port through which clients can access it. It then sits down and waits until somebody (the client) attempts to connect to it. When that happens, the server and client exchange some messages and ultimately of the two close the connection. This connection takes place using so-called sockets. 
The Server
The simplest version of such a server is non-threaded. That means that multiple connections are handled sequentially, in other words: clients have to queue up and they are handled one by one. That's fine if connections last only very short and if there are not too many clients connecting at the same time, however if you have many clients connecting at the same time or long-lasting connections you have to handle connections in parallel. You can handle multiple connections in parallel using threads. Each time a connection is established a new thread is created and the connection is handled by that new thread. The server thread then continues accepting new connections. Because creating threads is an expensive process (in terms of CPU cycles) threads are usually kept in a "pool". When a thread finished its job, it is kept alive until a new request has arrived it can handle. 
The Client
For the client to connect it has to know the server's IP or hostname and the port to connect to. Once the connection is established the client and server can exchange messages. Depending on the distributed system a client may connect to multiple servers. One server to access the database, one for file services

a protocol is the special set of rules that end points in a telecommunication connection use when they communicate.

On the Internet, there are the TCP/IP protocols, consisting of:

• Transmission Control Protocol (TCP), which uses a set of rules to exchange messages with other Internet points at the information packet level
• Internet Protocol (IP), which uses a set of rules to send and receive messages at the Internet address level
• Additional protocols that include the Hypertext Transfer Protocol(HTTP) and File Transfer Protocol (FTP), each with defined sets of rules to use with corresponding programs elsewhere on the Internet

recent Innovations

 Being able to controlling a computer with your voice.. IBM developed a new technology to make the Internet affordable, accessible and available to billions of  users around the world, without  a traditional computer.
In the next five years, you will be able to surf the Internet, hands-free, by using your voice. New technology will change how people create, build and interact with information using speech instead of text.

The Difference between Computing and ICT

ICT is the use of computer programs. The programs are used to make databases and spreadsheets. Whereas computing is programming and how the computer works.