Magnetic Hard Disk - 19.3 GB to 1.2 TB
Magnetic Floppy Disk - Up to 14 MB
Magnetic Tape - 10 to 800 GB
CD-ROM - Up to 700 MB
CD-R - Up to 700 MB
CD-RW - Up to 700 MB
DVD-ROM - Up to 17 GB
DVD-R - Up to 17 GB
DVD-RAM - Up to 17 GB
DVD-RW - Up to 17 GB
Blu-Ray Disc - Up to 50 GB
HD-DVD - Up to 51 GB
USB Flash Drive - Up to 5 GB
Memory Card - Up to 4 GB
Saturday, 6 November 2010
Storage Devices
Primary Storage - Is temporary storage that is quickly readable to the processor.
Secondary Storage - Is permanent storage for programs and other files that can be readily accessed by the computer, but at a slower speed than Primary Storage.
Magnetic
Hard Disk Drive - The disk allows rapid direct access to large amounts of data. The disk is also known as a platter. The platter is coated with an emulsion of iron and cobolt oxide particles that act as tiny magnets. Binary data is stored by aligning these tiny magnets in one direction to represent a 0 and another direction to represent a 1. Binary data is recorded in concentric rings, or tracks, which are subdivided into sectors that hold a fixed number of bytes. To read the data stored on the hard disk, the read-write head is moved to the desired track and waits for the relevant information to pass beneath it. When data is passed from the computer to the hard disk and vice versa, a whole sector is read or written each time. The top and bottom of the platter may be used to store data. Usually they are stored within a plastic box to restrict damage upon impact. The greater number of platters the more storage is available.
Floppy Disk - A very old form of storage that is used as operating system boot disks.
Magnetic Tape - Magnetic tape consists of a thin reel of plastic. The tape is coated on one side with a material that can be magnetised to record the bit patterns that represent data. The cartridge is completely sealed apart from an access door to put the tape in contact with the recording heads in the tape drive. Magnetic tape is robust, so it can be useful to transfer large pieces of data from one system to another. Finding a particular piece of data on a tape can take a long time, because the tape has to be searched from the beginning to the end. Although it is a cost-effective way to store data that does not have to be accessed immediately.
Optical
CD ROM - Read Only Memory. The data is written on the discs using disc-mastering machinery that impresses pits into the continuous spiral track. The disc surface contains a track that is 3.5 miles long. The disc spins at 200-500 revolutions and minutes. The data bit is read by a laser beam onto a point in the reflective metal layer where pits are impressed.
CD-R - The discs can be written only once. Any region can be written on but it cannot be altered. Data bits are recorded by burning a pit in a thin layer of film of metal using a high powered laser. A laser with much less power is used to read the disc. The recording beam creates a spot of less reflective disc by inducing a chemical reaction between the gold layer and it's dye coating.
CD-RW - A CD re-write can be read and written to as many times as you like. CD-RW drives have a magnet and a laser. The laser is similar to the one in the CD ROM drive. The write operations uses a magnet and the laser. The read operation only uses the laser. The data tracks are arranged in sectors. To record or change data the laser heats up a precise spot on the disc to around 200 degrees. The magnet is then used to set the state of the data bit at this spot. The disc cools and fixes this data bit. CD-RW drives keep the read-write heads a safe distance from the disc surface to avoid scratching. The laser light is less powerful as to not heat up the disc, it is polarised as it reflects off the surface and the degree of polarisation indicates the value of the data bit.
DVD-ROM - Offer more storage space compared to CD's. CD's and DVD's store data in the form of microscopic pits, which represent binary ones and zeros. A DVD can store more data due to the length of the pit size. In a CD the pits have to be a minimum length of 0.8 micro meters, however on a DVD they only have to be 0.4 micro meters allowing for more pits to be placed on the disc. To read the smaller pits the DVD drive uses a laser with a smaller wavelength. The red laser diodes used in DVD drives are identical to those in Bar Code Readers. Some manufacturers use both sides of the DVD disc to allow for more storage.
DVD-R - Record data by burning spots in the dye to alter the amount of laser light reflected.
DVD-RAM - Is a rewritable format that has a built in error control and a defect management system, so it is considered better than the other DVD technologies for tasks such as storage, backup and archiving data. RAM is used in camcorders and set top boxes as the data is easily rewritten and erased.
DVD-RW - The RW format provides a rewritable optical disc. They are commonly used for backing up data and home DVD recorders. One benefit of using a rewritable disc is that if there were writing errors while recording data then the data can be erased and stored on the disc again. The recording layer is not an organic dye, but a special phase-change metal back and forth between crystalline phase and an amorphous phase.
Blu-Ray Disc - A BD disc is a high density disc which stores digital information, including HDBD disc allows for quicker transfers of data.
HD-DVD - Works the same as Blu-Ray DVDs. They have become less popular as more people choose to buy BD discs.
Solid State
USB Flash Drive - A flash drive consists of a small printed circuit board typically in a plastic or metal casing. Only the USB connector is shown from the casing. Most USB Flash Drives uses a standard connection to allow it to be connected to a port on a computer easily. Flash drives are a relatively dense form of storage; even the cheapest flash drive can store all the data of a dozen floppy disks. They are generally more robust than Hard Disk Drives.
Memory Card - Usually used for storage in digital cameras, hand-held and laptop computers, telephones, music players, and games consoles. Memory cards offer a high capability for re-recording, power-free storage. They are generally more robust than Hard Disk Drives.
Secondary Storage - Is permanent storage for programs and other files that can be readily accessed by the computer, but at a slower speed than Primary Storage.
Magnetic
Hard Disk Drive - The disk allows rapid direct access to large amounts of data. The disk is also known as a platter. The platter is coated with an emulsion of iron and cobolt oxide particles that act as tiny magnets. Binary data is stored by aligning these tiny magnets in one direction to represent a 0 and another direction to represent a 1. Binary data is recorded in concentric rings, or tracks, which are subdivided into sectors that hold a fixed number of bytes. To read the data stored on the hard disk, the read-write head is moved to the desired track and waits for the relevant information to pass beneath it. When data is passed from the computer to the hard disk and vice versa, a whole sector is read or written each time. The top and bottom of the platter may be used to store data. Usually they are stored within a plastic box to restrict damage upon impact. The greater number of platters the more storage is available.
Floppy Disk - A very old form of storage that is used as operating system boot disks.
Magnetic Tape - Magnetic tape consists of a thin reel of plastic. The tape is coated on one side with a material that can be magnetised to record the bit patterns that represent data. The cartridge is completely sealed apart from an access door to put the tape in contact with the recording heads in the tape drive. Magnetic tape is robust, so it can be useful to transfer large pieces of data from one system to another. Finding a particular piece of data on a tape can take a long time, because the tape has to be searched from the beginning to the end. Although it is a cost-effective way to store data that does not have to be accessed immediately.
Optical
CD ROM - Read Only Memory. The data is written on the discs using disc-mastering machinery that impresses pits into the continuous spiral track. The disc surface contains a track that is 3.5 miles long. The disc spins at 200-500 revolutions and minutes. The data bit is read by a laser beam onto a point in the reflective metal layer where pits are impressed.
CD-R - The discs can be written only once. Any region can be written on but it cannot be altered. Data bits are recorded by burning a pit in a thin layer of film of metal using a high powered laser. A laser with much less power is used to read the disc. The recording beam creates a spot of less reflective disc by inducing a chemical reaction between the gold layer and it's dye coating.
CD-RW - A CD re-write can be read and written to as many times as you like. CD-RW drives have a magnet and a laser. The laser is similar to the one in the CD ROM drive. The write operations uses a magnet and the laser. The read operation only uses the laser. The data tracks are arranged in sectors. To record or change data the laser heats up a precise spot on the disc to around 200 degrees. The magnet is then used to set the state of the data bit at this spot. The disc cools and fixes this data bit. CD-RW drives keep the read-write heads a safe distance from the disc surface to avoid scratching. The laser light is less powerful as to not heat up the disc, it is polarised as it reflects off the surface and the degree of polarisation indicates the value of the data bit.
DVD-ROM - Offer more storage space compared to CD's. CD's and DVD's store data in the form of microscopic pits, which represent binary ones and zeros. A DVD can store more data due to the length of the pit size. In a CD the pits have to be a minimum length of 0.8 micro meters, however on a DVD they only have to be 0.4 micro meters allowing for more pits to be placed on the disc. To read the smaller pits the DVD drive uses a laser with a smaller wavelength. The red laser diodes used in DVD drives are identical to those in Bar Code Readers. Some manufacturers use both sides of the DVD disc to allow for more storage.
DVD-R - Record data by burning spots in the dye to alter the amount of laser light reflected.
DVD-RAM - Is a rewritable format that has a built in error control and a defect management system, so it is considered better than the other DVD technologies for tasks such as storage, backup and archiving data. RAM is used in camcorders and set top boxes as the data is easily rewritten and erased.
DVD-RW - The RW format provides a rewritable optical disc. They are commonly used for backing up data and home DVD recorders. One benefit of using a rewritable disc is that if there were writing errors while recording data then the data can be erased and stored on the disc again. The recording layer is not an organic dye, but a special phase-change metal back and forth between crystalline phase and an amorphous phase.
Blu-Ray Disc - A BD disc is a high density disc which stores digital information, including HDBD disc allows for quicker transfers of data.
HD-DVD - Works the same as Blu-Ray DVDs. They have become less popular as more people choose to buy BD discs.
Solid State
USB Flash Drive - A flash drive consists of a small printed circuit board typically in a plastic or metal casing. Only the USB connector is shown from the casing. Most USB Flash Drives uses a standard connection to allow it to be connected to a port on a computer easily. Flash drives are a relatively dense form of storage; even the cheapest flash drive can store all the data of a dozen floppy disks. They are generally more robust than Hard Disk Drives.
Memory Card - Usually used for storage in digital cameras, hand-held and laptop computers, telephones, music players, and games consoles. Memory cards offer a high capability for re-recording, power-free storage. They are generally more robust than Hard Disk Drives.
Output Devices
Output Devices - A peripherals used to present or get the results of a computers work to the outside.
Displays
Cathode Ray Tube (CRT) - Is a vacuum tube with a narrow neck and a flat rectangular base. The screen is coated on the inside with a phosphor that emits light when struck by an electron beam. The electron beam is produced by an electron gun which dragged across the screen a line at a time so it covers every horizontal line of the screen. CRT's use three different types of electron gun, red, green and blue. the screen is made up of phosphor dots which are arranged in triplets and each triplet consists of a red, green and blue phosphor.
Liquid Crystal Display (LCD) - Electric crystals can change the polarisation of light when an electric field is applied to them. A LCD display is a matrix of liquid crystal cells and each cell constitutes a pixel when the screen is used at full resolution.For colour displays each pixel is divided into three or four sub pixels covered with coloured filters for additive mixing of red, blue and green.
Plasma Screen - Plasma screens are ideal for large displays. Each pixel is controlled by a miniature fluorescent light. When the control voltage is applied the gas becomes plasma and releases UV light, which strikes phosphors on the front of the screen to emit visible light. Plasma screens generate a lot of heat, enough to burn if you touch them.
Printers
Ink jet Printer - An ink jet printer produces coloured output by printing a line at a time. Coloured ink jet printers use three colours; Cyan, Magenta and Yellow. Ink jet printers can be slow when printing in the highest resolution and the ink can smudge. For the very best quality, special paper is required. Also you have to buy cartridges every couple of months, which are expensive.
Laser Printer - A laser printer prints a whole page at a time. It prints high quality text and graphics on plain paper. A negative charge is applied to the photosensitive drum at the heart of the printer. One or more laser beams are directed onto the rotating drum's surface. The lasers are turned on and off at positions determined by the bitmap data stored in the raster memory. This causes the negative to be neutralised or reversed at positions corresponding to the black parts of the page to be printed. The charged surface of the drum is exposed to toner, fine particles of dry plastic powder which is mixed with carbon black. The toner particles are given a negative charge so they attach to the positive charged parts of the drum. Which is then transferred to paper.
Impact Printer (Dot Matrix) - A Printer that only prints in black & white and can only print text, it uses a similar structure of a type writer to print the text, as it stamps the letters onto the page. They use a ink ribbon to mark the paper with an impression of a character. In a Dot Matrix printer the ribbon is struck by up to 24 metal pins that form the outline of a character.
Plotter - A plotter moves a pen across paper in a continuous movement so that the two-dimensional drawing can be made. The pen is lifted when it is not drawing on the paper and is lowered to draw and mark the paper. In a drum plotter, a roll of paper at least one meter wide is fed over a drum. The pen is located above the paper and is constrained to move the length of the drum in a straight line. A drum plotter is used to produce engineering drawings (blueprints) to a very large scale, it is also used for producing posters for billboards for example.
Other
Sound - Usually given out via speakers
Displays
Cathode Ray Tube (CRT) - Is a vacuum tube with a narrow neck and a flat rectangular base. The screen is coated on the inside with a phosphor that emits light when struck by an electron beam. The electron beam is produced by an electron gun which dragged across the screen a line at a time so it covers every horizontal line of the screen. CRT's use three different types of electron gun, red, green and blue. the screen is made up of phosphor dots which are arranged in triplets and each triplet consists of a red, green and blue phosphor.
Liquid Crystal Display (LCD) - Electric crystals can change the polarisation of light when an electric field is applied to them. A LCD display is a matrix of liquid crystal cells and each cell constitutes a pixel when the screen is used at full resolution.For colour displays each pixel is divided into three or four sub pixels covered with coloured filters for additive mixing of red, blue and green.
Plasma Screen - Plasma screens are ideal for large displays. Each pixel is controlled by a miniature fluorescent light. When the control voltage is applied the gas becomes plasma and releases UV light, which strikes phosphors on the front of the screen to emit visible light. Plasma screens generate a lot of heat, enough to burn if you touch them.
Printers
Ink jet Printer - An ink jet printer produces coloured output by printing a line at a time. Coloured ink jet printers use three colours; Cyan, Magenta and Yellow. Ink jet printers can be slow when printing in the highest resolution and the ink can smudge. For the very best quality, special paper is required. Also you have to buy cartridges every couple of months, which are expensive.
Laser Printer - A laser printer prints a whole page at a time. It prints high quality text and graphics on plain paper. A negative charge is applied to the photosensitive drum at the heart of the printer. One or more laser beams are directed onto the rotating drum's surface. The lasers are turned on and off at positions determined by the bitmap data stored in the raster memory. This causes the negative to be neutralised or reversed at positions corresponding to the black parts of the page to be printed. The charged surface of the drum is exposed to toner, fine particles of dry plastic powder which is mixed with carbon black. The toner particles are given a negative charge so they attach to the positive charged parts of the drum. Which is then transferred to paper.
Impact Printer (Dot Matrix) - A Printer that only prints in black & white and can only print text, it uses a similar structure of a type writer to print the text, as it stamps the letters onto the page. They use a ink ribbon to mark the paper with an impression of a character. In a Dot Matrix printer the ribbon is struck by up to 24 metal pins that form the outline of a character.
Plotter - A plotter moves a pen across paper in a continuous movement so that the two-dimensional drawing can be made. The pen is lifted when it is not drawing on the paper and is lowered to draw and mark the paper. In a drum plotter, a roll of paper at least one meter wide is fed over a drum. The pen is located above the paper and is constrained to move the length of the drum in a straight line. A drum plotter is used to produce engineering drawings (blueprints) to a very large scale, it is also used for producing posters for billboards for example.
Other
Sound - Usually given out via speakers
Tuesday, 2 November 2010
Input Devices
Input Devices - A peripheral used to get data and instructions into the computer system.
General
Mouse - It works by detecting the movement of the X and Y axis, it also has 2 or 3 buttons, left, right and scroll (middle).
Microphone (Voice Recognition) - Computer detects speech which turns it into text, using a microphone and sound card with appropriate software.
Graphics Tablet - Allows Graphics to be drawn into a computer by hand. It is a flat board is connected to the computer. It uses a stylus to detect the movement across the surface of the tablet. adding pressure to the surface operates a micro switch, which allows the computer to record movement. The board contains electronics to detect the position of the stylus tip.
Keyboard - Used to enter text into the computer system. the electrical components scan the rows of keys to detect the pressing of a key or key combination. When a key is pressed it sends the key's scan code to the computer. The software in the computer translates the scan code into ASCII or Unicode.
Touch Sensitive Screens - Is a type of visual display which allows the user to interact with an application. The screen has been adapted by having horizontal and vertical infrared beams, the breaking of these beams allows the system to detect where movement is on the screen.
Digital Still Camera - A digital camera is an electronic device used to capture images and videos onto an SD Card which then allows you to upload to your computer by USB.
Readers
Smart Card Reader - A smart card is a plastic card the size of a credit card that holds an integrated micro chip. The chip contains a microprocessor, which contains a small amount of ROM and a small amount of RAM.
Magnetic Stripe Reader - Magnetic stripe readers read information encoded magnetically in a stripe on the back of a plastic or cardboard card. The stripe is used to encode binary data. They are often used on Debit and Credit Cards.
Bar Code Reader - Is an electronic device for reading bar codes printed on items such as cans. A bar code is a sequence of white and black bars that encodes information such as a product identifier. The reader consists of a light source, the light source illuminates the black and white bands, light is reflected from the white and not from the black. the pattern of the bar code is then converted from optical form to electrical form. This is done by photo electronic detectors.
Optical Mark Reader - An optical mark reader senses marks placed on predefined positions on a form. The form is passed under a light source and the intensity of reflected light from each row of the form is measured and converted by photoelectric sensors into an electrical equivalent.
Optical Character Recognition - Uses an optical scanner to input images of text then analyse the resulting digital images to recognise the characters.
Radio Frequency Identification - Uses radio frequencies to transmit data, a timing signal and energy between the reader and an RFID device.
Scanners
Finger Print Scanner - A fingerprint reader is a security device that takes a picture of a finger so that the pattern of the ridges and valleys in the image can be analysed. It consists of a sensor and decoder circuitry to analyse the captured image data and output it on a computer against stored fingerprint data in a database.
Flatbed Scanners - Usually has a glass plane illuminated from beneath by a bright light, often xenon or cold-cathode fluorescent. An array of light detecting sensors spanning the width of the glass pane is moved slowly with the light source along the glass plane to pick up light reflected from anything placed on top of the plane. Coloured scanners usually use three different types of arrays.
Retina Scanner - Consists of a low energy infrared light source which is directed onto the retina of the eye. Each persons retina is unique. The photoelectric sensors convert the results into readable form on a computer.
Iris Scanner - Is a flat circular coloured membrane suspended vertically in the aqueous of the human eye. It uses a camera which is sensitive to infrared light and is placed no more than 3 ft from the subject to capture the image of the iris and compare this to data in a database .
General
Mouse - It works by detecting the movement of the X and Y axis, it also has 2 or 3 buttons, left, right and scroll (middle).
Microphone (Voice Recognition) - Computer detects speech which turns it into text, using a microphone and sound card with appropriate software.
Graphics Tablet - Allows Graphics to be drawn into a computer by hand. It is a flat board is connected to the computer. It uses a stylus to detect the movement across the surface of the tablet. adding pressure to the surface operates a micro switch, which allows the computer to record movement. The board contains electronics to detect the position of the stylus tip.
Keyboard - Used to enter text into the computer system. the electrical components scan the rows of keys to detect the pressing of a key or key combination. When a key is pressed it sends the key's scan code to the computer. The software in the computer translates the scan code into ASCII or Unicode.
Touch Sensitive Screens - Is a type of visual display which allows the user to interact with an application. The screen has been adapted by having horizontal and vertical infrared beams, the breaking of these beams allows the system to detect where movement is on the screen.
Digital Still Camera - A digital camera is an electronic device used to capture images and videos onto an SD Card which then allows you to upload to your computer by USB.
Readers
Smart Card Reader - A smart card is a plastic card the size of a credit card that holds an integrated micro chip. The chip contains a microprocessor, which contains a small amount of ROM and a small amount of RAM.
Magnetic Stripe Reader - Magnetic stripe readers read information encoded magnetically in a stripe on the back of a plastic or cardboard card. The stripe is used to encode binary data. They are often used on Debit and Credit Cards.
Bar Code Reader - Is an electronic device for reading bar codes printed on items such as cans. A bar code is a sequence of white and black bars that encodes information such as a product identifier. The reader consists of a light source, the light source illuminates the black and white bands, light is reflected from the white and not from the black. the pattern of the bar code is then converted from optical form to electrical form. This is done by photo electronic detectors.
Optical Mark Reader - An optical mark reader senses marks placed on predefined positions on a form. The form is passed under a light source and the intensity of reflected light from each row of the form is measured and converted by photoelectric sensors into an electrical equivalent.
Optical Character Recognition - Uses an optical scanner to input images of text then analyse the resulting digital images to recognise the characters.
Radio Frequency Identification - Uses radio frequencies to transmit data, a timing signal and energy between the reader and an RFID device.
Scanners
Finger Print Scanner - A fingerprint reader is a security device that takes a picture of a finger so that the pattern of the ridges and valleys in the image can be analysed. It consists of a sensor and decoder circuitry to analyse the captured image data and output it on a computer against stored fingerprint data in a database.
Flatbed Scanners - Usually has a glass plane illuminated from beneath by a bright light, often xenon or cold-cathode fluorescent. An array of light detecting sensors spanning the width of the glass pane is moved slowly with the light source along the glass plane to pick up light reflected from anything placed on top of the plane. Coloured scanners usually use three different types of arrays.
Retina Scanner - Consists of a low energy infrared light source which is directed onto the retina of the eye. Each persons retina is unique. The photoelectric sensors convert the results into readable form on a computer.
Iris Scanner - Is a flat circular coloured membrane suspended vertically in the aqueous of the human eye. It uses a camera which is sensitive to infrared light and is placed no more than 3 ft from the subject to capture the image of the iris and compare this to data in a database .
Wednesday, 20 October 2010
Hardware and Software
Hardware - Electronic parts of a computer - Processor, Input and Output devices.
Software - Data which runs on the hardware - Programs
Software - System Software - Operation Systems - Operate the Hardware. e.g. Windows, MAC, Linux
- Library Programs - Common Functions.
- Utility Programs - Specific tasks.
- Translators - Turns higher level language into machine code.
- Application Software - General Purpose - Can be used for a number of tasks.
- Special Purpose - Supports one specific task.
- Bespoke - Software that is tailored.
Software - Data which runs on the hardware - Programs
Software - System Software - Operation Systems - Operate the Hardware. e.g. Windows, MAC, Linux
- Library Programs - Common Functions.
- Utility Programs - Specific tasks.
- Translators - Turns higher level language into machine code.
- Application Software - General Purpose - Can be used for a number of tasks.
- Special Purpose - Supports one specific task.
- Bespoke - Software that is tailored.
Ports
HTTP - (Web Browser) Port 80
HTTPS - (Web Browser (Safe)) Port 443
FTP - (File Transfer) Port 20
SMTP - (Sending E-mail) Port 25
POP3 - (Receiving E-mail) Port 110
HTTPS - (Web Browser (Safe)) Port 443
FTP - (File Transfer) Port 20
SMTP - (Sending E-mail) Port 25
POP3 - (Receiving E-mail) Port 110
TCP/IP Stack
TCP - Transport Control Protocol - Breaks data down into packets.
IP - Finds a computer on a network to route the packets of data to.
Layer 1 - Application Layer - Specific networking applications e.g. web browser, word processor
Layer 2 - Transport Layer - Breaks data down into packets and adds a sequence number to each packet, also adds source and destination ports.
Layer 3 - Network Layer - Adds the source IP address and the destination IP address to the packets.
Layer 4 - Link Layer - Adds source and host hardware addresses and puts packets on the cable.
Host Hardware - Media Access Control (MAC)
IP - Finds a computer on a network to route the packets of data to.
Layer 1 - Application Layer - Specific networking applications e.g. web browser, word processor
Layer 2 - Transport Layer - Breaks data down into packets and adds a sequence number to each packet, also adds source and destination ports.
Layer 3 - Network Layer - Adds the source IP address and the destination IP address to the packets.
Layer 4 - Link Layer - Adds source and host hardware addresses and puts packets on the cable.
Host Hardware - Media Access Control (MAC)
End of Topic Assignment - The Internet
Before leaving work Bob logs onto his work computer. He uses the intranet, a part of the internet that is used only for businesses, to look up some information of a colleague. He uses a simple mail transfer protocol, SMTP, to send them an e-mail containing a link on the extranet; it is sent to the staff only e-mail notice board.
Bob then goes home, meanwhile after the e-mail had been sent the transport layer (TCP Layer) this is where the e-mail is broken down into packets of data and adds the source and destination ports to the packets as well as the sequence number; that way if a packet gets there quicker than another packet that was before it then the packets will be placed back in order. Then it goes to the network layer also known as the IP Layer, this is where the source and destination IP addresses are added, this is so the packet knows where to be delivered to. After the IP Layer the link layer adds the hardware addresses to each packet, the hardware addresses are also known as MAC Addresses, and puts them on the cable.
At home Bob uses his internet service provider to access the web. He uses this is access the Amazon webpage, using the HTTP protocol. The request is from the client to the host server. The client requests the web page from the application layer and the moves it way down the TCP Layer which adds a port number, which will be port 80 due to it being a web page, it will also add the sequence number to the packet of data that it has been split into. The packet is then passed to the IP layer where the source IP address is and where the destination IP address is. The packet is then once again passed down to the link layer where the MAC address is added so that the packet is added to the cable, for it to be sent. The packet is now sent across the local area network, which is a network that computers and other servers use to relay information. The local router for this local area network reads the address that the packet has and routes it to the right destination. When the packet arrives at the client server it goes up the layers back to the application layer. At the network layer the IP addresses are removed and then the transport layer reconstructs the data to be looked at on the application layer, which in this case is the web page Amazon. The web page is shown in the internet, which is a network of networks that allows a number of computers to gain information from other computers around the world. The packets have to make their way through the firewall to get to the web browser to show the page. The firewall stops untrusted data from gaining access to your computer and your files. You’re home network works like a sort of intranet as it only allows you to gain access to files and information on that network but also allows you to access information on the extranet. The packets that bob has sent will be processed to be directed to port 80 which is where all web pages are sent. Once the web page has been found the data is sent back along the path (through all the layers in the TCP/IP stack) back to the client (Bob). Bob buys a present for Alice on the Amazon website, he then uses the POP3 protocol to check for any new mail, POP3 is used for receiving e-mails and SMPT is used for sending e-mails, after checking for new e-mails he sends Alice an e-mail about the present, this will then go through all the layers and through port 25 which is the standard e-mailing port.
Monday, 4 October 2010
Useful Definitions
Packets - part of a large piece of information
- Contains three parts - Header - Senders IP Address
- Recievers IP Address
- Protocal (HTTP)
- Packet Number
- Payload - The Actual Data
- Trailer - Data to show the end of the Packet
- Error Corrections
Router - a specialised piece of computer equipment which recieves and sends packets, the router recieves the packet and then forwards them onto the right computer.
Domain Name - Easily Recognised and easy to remember
- Example - www.google.com
Protocol - Specifies what path the computer should follow to access the requested file.
Domain - Points to the website where the file is.
Path - The route the internet takes to get to the file being requested.
File Name - The name of the file.
IP Address - a unique number allocated to every computer
- Made up of 4 sets of 3 digit numbers (86.134.238.10)
Domain Name Server (DNS) - Translates IP addresses into recognizable domains.
Internet Registries and Registras - Registries - Number
- Registras - Name
- Manages IP Addresses and Domain Names
Internet Service Provider (ISP) - Provides an entrance to the internet.
Intranet - a closed off portion of the internet within a single location for example within a business.
Extranet - a piece of an organisations intranet which has been made securely available to other oganisations or individuals.
Clients - Main job is to recieve information. It is a computer on a network using resources provided by the server.
Servers - Main job is to send information. It is a computer on a network that provides resources for clients.
URI - Uniform Resource Identifier - Provides a unique ID
URN - Unique Resource Name - The unique name for something e.g. isbn numbers.
URL - Uniform Resource Locator - Unique location of something e.g. website address.
Program Control Unit (PCU) - Fetches programs from memory and executes them one at a time.
Arithmetic and Logic Unit (ALU) - Performs logical operations when instructed by programs.
Registers - Fast memory locations within the processor.
System Clock - Sends out ticks to sync the operation of the components (measured in GHz)
Internal Bus - Buses within the processor which alllow the PCU & ALU to communicate.
Dedicated Registers - Assigned a specific purpose by the designer of the processor.
General Purpose Register - Available for the programmer to store data temporarily.
Accumulator (ACC) - Holds the result of calculations.
- Contains three parts - Header - Senders IP Address
- Recievers IP Address
- Protocal (HTTP)
- Packet Number
- Payload - The Actual Data
- Trailer - Data to show the end of the Packet
- Error Corrections
Router - a specialised piece of computer equipment which recieves and sends packets, the router recieves the packet and then forwards them onto the right computer.
Domain Name - Easily Recognised and easy to remember
- Example - www.google.com
Protocol - Specifies what path the computer should follow to access the requested file.
Domain - Points to the website where the file is.
Path - The route the internet takes to get to the file being requested.
File Name - The name of the file.
IP Address - a unique number allocated to every computer
- Made up of 4 sets of 3 digit numbers (86.134.238.10)
Domain Name Server (DNS) - Translates IP addresses into recognizable domains.
Internet Registries and Registras - Registries - Number
- Registras - Name
- Manages IP Addresses and Domain Names
Internet Service Provider (ISP) - Provides an entrance to the internet.
Intranet - a closed off portion of the internet within a single location for example within a business.
Extranet - a piece of an organisations intranet which has been made securely available to other oganisations or individuals.
Clients - Main job is to recieve information. It is a computer on a network using resources provided by the server.
Servers - Main job is to send information. It is a computer on a network that provides resources for clients.
URI - Uniform Resource Identifier - Provides a unique ID
URN - Unique Resource Name - The unique name for something e.g. isbn numbers.
URL - Uniform Resource Locator - Unique location of something e.g. website address.
Program Control Unit (PCU) - Fetches programs from memory and executes them one at a time.
Arithmetic and Logic Unit (ALU) - Performs logical operations when instructed by programs.
Registers - Fast memory locations within the processor.
System Clock - Sends out ticks to sync the operation of the components (measured in GHz)
Internal Bus - Buses within the processor which alllow the PCU & ALU to communicate.
Dedicated Registers - Assigned a specific purpose by the designer of the processor.
General Purpose Register - Available for the programmer to store data temporarily.
Accumulator (ACC) - Holds the result of calculations.
Wednesday, 22 September 2010
Colours & Markup Validation Service
Adobe Kuler allows us to select a range of colour rules.
The three main ones I need are Analogous, Monochromatic and Complementary.
What is Analogous?
If you think of the colour wheel as wedges of a pie, the colors in one-fourth of the pie are analogous. Three colors next to each other on the colour wheel comprise an analogous colour scheme.
What is Monochromatic?
In this type of scheme, various darker shades, grayer tones, and paler tints of the main colour may be included in the palette.
What is Complementary?
A complementary colour scheme uses colours across the colour wheel from each other as the main focus
Markup Validation W3C - http://jogport.johnofgaunt.wilts.sch.uk/moodle/mod/resource/view.php?id=2170
The three main ones I need are Analogous, Monochromatic and Complementary.
What is Analogous?
If you think of the colour wheel as wedges of a pie, the colors in one-fourth of the pie are analogous. Three colors next to each other on the colour wheel comprise an analogous colour scheme.
What is Monochromatic?
In this type of scheme, various darker shades, grayer tones, and paler tints of the main colour may be included in the palette.
What is Complementary?
A complementary colour scheme uses colours across the colour wheel from each other as the main focus
Markup Validation W3C - http://jogport.johnofgaunt.wilts.sch.uk/moodle/mod/resource/view.php?id=2170
An Important Computing Innovation
Skype
Skype is a software application like instant messenger (msn) that allows the user to interact with people face to face over the internet or web. People can makevoice calls for free instead of using the landline. Skype allows users to use webcams and voices to communicate with the other user they are talking to, compared to msn this is better because msn does not use voices. Skype has adapted over the years to be able to do file transfers and instant messenging and video confrencing; for example if a businessman is in the UK but wants to make a business call to China, all he needs to have is skype and a webcam, this will allow him to see, hear and speak while the business in china listen.
This has made video confrencing easier to use and navigate. I do not use skype a lot but I have it incase I ever need it :)
Skype is a software application like instant messenger (msn) that allows the user to interact with people face to face over the internet or web. People can makevoice calls for free instead of using the landline. Skype allows users to use webcams and voices to communicate with the other user they are talking to, compared to msn this is better because msn does not use voices. Skype has adapted over the years to be able to do file transfers and instant messenging and video confrencing; for example if a businessman is in the UK but wants to make a business call to China, all he needs to have is skype and a webcam, this will allow him to see, hear and speak while the business in china listen.
This has made video confrencing easier to use and navigate. I do not use skype a lot but I have it incase I ever need it :)
HTML The Essentials
Example: <ISBN>124789-00A</ISBN>
The ISBN gives the middle part a meaning or in other words a context.
Need To Knows:
<html> - </html> Start and end of the design
<p> - </p> Paragraphs
<strong> - </strong> Bold
<em> - </em> Italics
<ol> </ol> Ordered Numerical List
<br/> Self Closing
<a href>= "(website address)"</a href> Links & References
<img src>="(location of image)</img> Images
http://jogport.johnofgaunt.wilts.sch.uk/moodle/mod/resource/view.php?id=2267
The ISBN gives the middle part a meaning or in other words a context.
Need To Knows:
<html> - </html> Start and end of the design
<p> - </p> Paragraphs
<strong> - </strong> Bold
<em> - </em> Italics
<ol> </ol> Ordered Numerical List
<br/> Self Closing
<a href>= "(website address)"</a href> Links & References
<img src>="(location of image)</img> Images
http://jogport.johnofgaunt.wilts.sch.uk/moodle/mod/resource/view.php?id=2267
What Is A Markup Language?
A markup language is a coding system, such as HTML and SGML, used to structure, index and link text files. A standard text coding system consists of a set of symbols inserted in a text document to control it's formatting and structure, the symbols are then processed which tells a screen or printer how the document should look.
What Is The Difference Between The Internet & The WWW?
The Internet
The internet is a massive network of networks, it connects millions of computers together globally; forming a network in which any computer can communicate with any other computer as long as they are both connected to the internet. Information that travels across the internet is done so in a variety of languages called protocols.
The World Wide Web (www)
The internet is a massive network of networks, it connects millions of computers together globally; forming a network in which any computer can communicate with any other computer as long as they are both connected to the internet. Information that travels across the internet is done so in a variety of languages called protocols.
The World Wide Web (www)
The web is an information-sharing model that is built on top of the Internet. The Web uses the HTTP protocol, only one of the languages spoken over the Internet, to transmit data. Web services, which use HTTP to allow applications to communicate in order to exchange business logic, use the the Web to share information. The Web also utilizes browsers, such as Internet Explorer or Firefox, to access Web documents called Web pages that are linked to each other via hyperlinks. Web documents also contain graphics, sounds, text and video,
Tuesday, 7 September 2010
What is the difference from Computing and ICT?
Ict has a more practical side to the subjest, for example using software programmes and the uses of applications; using spreadsheets and databases. Computing on the other hand includes the use of programming language and the technical side of how the software used in ICT is created.
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