Year 10 Notes

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Y10 Lorena
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Última modificación 18 de diciembre de 2008
Term 3
Summary Of Data Logging and Quiz
The term 'data logging' refers to collecting or gathering data over a period of time.
Sensors are used to take readings or measurements at regular intervals of their environment. Sensors collect data of such as temperature, humidity, pressure, wind, speed, water currents, electrical voltage, pH readings etc. The sensors can be digital or analogue. If they take analogue readings, an Analogue to Digital Converter (ADC) will be needed to convert the signal into digital data which the computer can understand. As the sensor reads, the data is sent though a cable to a data logger. The data logger stores data for a period of time until is sent to the computer in large amounts. A data logger is hand-held battery-operated device which has lot of memory.
In a hospital patients with large illness danger are send to the Intensive Care Unit (ICU), while they are there they will be monitored to make sure that their health is stable and not deteriorating. Heart monitors will make reads of there heart rate and pattern of beats, these readings will be displayed as digital numbers in the monitor and continuously in a graph. There breath rate monitored and level of oxygen measured. Alarms will sound if oxygen levels go down. There temperature will be measured regularly to monitor if they have an infection or if it responding to the treatment.
Water companies have to monitor the acidity of the water in their reservoirs; they also monitor pollution, chemicals and number of bacteria in a river. In order to do this the sensor takes measurements of the water, the ADC change the signals, the data is send to the logger and then to the computer, Software analyses the data, Results presented in a graph and the results are printed out.
Racing car companies invest millions developing state of the art racing cars. They want to know if their car is performing well so if ensure the engine is calibrated correctly, the right amount of fuel is being delivered, the best speeds are being achieved etc. Digital electronic dashboards are used inside the cars. Display data by sensors. Data is logged for later analyzed by the engineers. Output alarms to alert driver of conditions. Data can also be scrolled through by the driver pushing a button.
Data often needs to be collected from places that are nowhere near an office. Data may be collected at all times, when people are away. As well may be collected from dangerous places or not safe for humans or can may be collected from ocean or other planet. Remote data logger means that sensors get data and send it to a portable data logger. The data logger then sends the data by satellite or other to a computer for analysis.
The 'Logging Interval' is the period of time over which measurements are taken by the sensors. If measurements change time interval as well, otherwise events will be missed and the other way round.
Logging Intervals
Data Logging
Typical Interval
Sound recording
Thousandth of a second
Heart beat
Tenths of a second
Oven temperature
Outdoor temperature
Soil dampness
Growth of plants
Destruction of the Rain Forest
Growth of cities
Global warming

· Data Logging can be used in remote or dangerous situations
· Data logging can be carried out 24 hours a day, 365 days of the year
· Time intervals for collecting data can be very frequent and regular, for example, hundreds of measurements per second
· can be set up to start at a time in the future
· No need to have a person present
· Data logging is often more accurate because there is no likelihood of human error
· If the data logging equipment breaks down or malfunctions, some data could be lost or not recorded
· Equipment can be expensive for small tasks
· The equipment will only take readings at the logging interval which has been set up. If something unexpected happens between recordings, the data will not be collected.

Sensors take readings or measurements of physical quantities around them.

Which of the following would a sensor NOT is used to take readings about?
Time of day.
If a sensor takes analogue readings, which of the following would be needed to convert the data into a digital format?


After the sensor has taken a reading, the data is sent to…
A Data Logger.
Data Loggers aren’t able to store the readings from the sensors, so they have to send them immediately to the computer.
Data Loggers often have a large amount of memory so that they can store a large amount of data from the sensors.
The data logger will send the data received from the sensors to the computer in a.
Sometimes data needs to be collected from places that are hard to reach or dangerous for a human e.g. a volcano. This is called… data logging.
The logging ‘interval’ or ‘period’ is the time.
The time between readings.
Data logging can be carried out 24 hours a day.
When the computer receives the data from the data logger, a program will analyses that data and produce a leaflet about the results.
Data which has been analyses by the computer is usually output in tables and also as graphs or charts.
Exam 4 (Page 2) Exam 4 (Page 1)external image m0hsx.jpg Exam 3 (Page 4) external image 2qimpls.jpg
You got a record that doesn't belong there... did you use autofilter to filter out the small sized records? Or did you just edit them out yourself one by one? sorry can't give you this one... talk to me in class... 0/10 (8/10 whole test)
Where's the P.E. data model? the one with the Skills performance analysis.

Exam 3 (Page 3)external image 34j5gdg.jpg
NIcely done! 10(10
Exam 3 (Page 2)external image j10tx2.jpg
Great! 10/10
Exam 3 (Page 1)external image 98x4oy.jpg
Where are the formulae? read the question again... I can see them in the one's above but you still had to show the mhere... 8/10


Excellent! 10/10 (whole test)
Exam 2 (Page1) external image 300cnjp.jpgExam 2 (Page 2)external image 34eq347.jpgExam 2 (Page 1 with Calculations)external image 2j2jiad.jpg
Excellent work! 10/10 I love the titles on the notes, makes it really easy to correct! :)
Exam 2 (Page 2 with Calculations)external image 2ue5vd0.jpgExam 2 (Page 3 with Calculations)external image hv6lnb.jpgExam 2 (Page 4 with Calculations)external image fxv7r5.jpgexternal image ohv9f9.jpg
Great Job! 10/10 (whole test)
Term 2
external image axnr60.jpg external image keyboard_history-1111.jpg With the red and purple finger the space is showned up.With the finger green and dark green the space is showned up.With the finger yellow and dark yellow the space is showned up.With the finger dark blue and blue the space is showned up.With the fingers white the space is showned up.
Nice :) 10/10

Excel lesson 3 worksheet

No of milkshakes drunk




Write formulas to calculate
  1. the total number of milkshakes drunk in a year
= Sum (B2:B13).
  1. The number of months in which milkshakes were drunk
= Count (B2:B13).
  1. The average number of milkshakes drunk / month
= Average (B2:B13)
  1. How many months more than 120 milkshakes were drunk
= Count If (B2:B13<120)
  1. Add a new column, and using the IF function write a comment on the number of milkshakes drunk.
IF more than 120 are drunk write “many drunk” if less than 120 write “few drunk”


  1. Add a new column labelled Price. If the quantity is greater than 100, write 0.5 and less than 100 write 0.6
  2. Add a new column called Total Cost. This column multiplies the price by the quantity.
  3. Underneath the table write VAT=, and in the adjacent cell write 17.5%.
  4. Add two columns which calculate
    1. VAT of the total cost
    2. Total cost + VAT

Excellent work! 10/10
Excel Task 1external image 36695509.png
Nice work 10/10

= SUM (A1:A125) means add.
= COUNT (A1:A10) means count.
= COUNTIF (A1:A100, >5) meant count the cells that are greater than 5.
=AVERAGE (A1:B10) means average.
= A15*$B$1 means multiply.

Good job 10/10 (Notes)

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Good work 10/10 (Please organize your notebook into sections and stick to the sections)

Microsoft Excel

Microsoft Excel is a spreadsheet. A spreadsheet is an application program that allows text, numbers and formulas to be entered into a grid. Spreadsheets are made of columns and rows which are divided into particular cells. In the cells you can do formulas. Formulas are equations that tell the spreadsheet what actions you wish to take on any spreadsheet data. Formulas are made up of functions. Functions are-ready-made formulas that have been built into the spreadsheet.

SGood, although I wouldn't say Ms Excel is a sopreadsheet... It's a program that simulates a spreadsheet used for modelling data... 10/10 (notes)

Data Analysis
Symbols used in formulas
What it does
Adds cells together
Subtract cells together

Multiplies cells

Divides cells
Equal to
Greater than
Greater than or equal to
Range of cells

MS Excel functions
What it does
Adds all the highlighted cells together
e.g =SUM(B1:B124) adds the values of all cells between B1 and B124.
Calculates the average of a range of cells
e.g. =AVERAGE (B1:B3) Calculates your average score.
Counts the number of cells that meet the given criteria.
e.g. =COUNTIF(D1:D30,”=A”) To find out how many students got grade A.
Count the number of cells that contain numbers
e.g. =COUNT (C1: C30) To count up the number of students who have paid in money.
Spreadsheet makes a choice depending on what it finds. It returns one of two values depending on the condition that you set.
e.g. = IF(D1<=2,Ask Mum for a loan!”,” Money Ok”) How much money you have left.

1. What is a spreadsheet?A spreadsheet is an application program that allows text, numbers and formulas to be entered into a grid of rectangular cells.2. What is a formula?A formula is an equation that tells the spreadsheet what actions you wish to take on any spreadsheet data.3. What is a function?A function are-ready- made formulas that hve been built into the spreadsheet.
Excellent 10/10 (notes)
external image 30921311cq6.png Storage Device

Solid state
Floppy disk
Pen drive

Storage devices are pieces of equipment that are used to store the data used by a computer, such as a floppy disk drive. Storage media are the actual materials on which the data is stored, such as a floppy disk.
Note spelling: disk (USA), disc (UK), you can use either but you must be consistent.

void(0); - data is stored as magnetic fluctuations along the length of a specially coated plastic tape, similar to the common audio tape. The coded data is processed (or translated) into useful information by the computer. Very slow, as need to wind tape (perhaps a long way) to find any specific position. Can hold thousands of **megabytes (MB)** of data depending on the length of the tape. Useful for daily backups of all work and programs on a large network, can be set to run automatically during the night and then will only be needed for disaster recovery where a reliable restoration is more important than speed. Can be damaged by stray magnetic fields from electrical equipment.

void(0); - data is stored magnetically and uses a material similar to tape. It needs to be formatted to provide a layout of tracks and segments to organise where the data is stored. One spin of the disk provides access to all the data hence much faster access than tape (about 36 KB per second) but it only starts spinning when requested. Each disk can hold only 1.44 megabytes of data. Good for transferring work and small programs between computers and for backing up your work projects, but is easily damaged if carried around unprotected and heavily used. Easily damaged by magnetic fields such as that produced by speakers and mobile phones. Disks cost less than £0.20 and a disk drive costs around £2, if available at all these days. Now totally superseded by the USB Memory Stick as a means of mobile storage.


Floppy disk



360 A4 pages

void(0); - made of stronger material (aluminium) and fixed permanently together with its drive mechanism inside the computer. Data is stored magnetically. Spinning at the required speed all the time it is very much faster to access than a floppy disk or CD-ROM (faster than 1 MB per second). Can hold thousands of megabytes (gigabytes) of data. Used for storing all programs and work files for very fast access by the computer. Can be damaged by stray magnetic fields but reasonable safe when kept inside the computer. Cost around £40.00 (40GB). Other common sizes are 80 and 120GB.

Internal memory (ROM/RAM)

Hard disk


Floppy disk







Removable-disk ('Zip') hard drives - two sizes most common are 100MB and 250MB. Zip disks, being about the same physical size as the floppy disk once became a popular replacement as a mobile means of storage but now totally superseded by the USB Memory Stick.

void(0); () - uses laser (light) technology to store the data. Comes with the data already on it for reading only (ROM = Read Only Memory) and hence cannot be written to for everyday storage. Like a floppy disk it has to spin up to the correct speed each time it is accessed. Much faster to access than a floppy but currently slower than a hard disk (single-speed 15 KB per second so a 40X speed CD-ROM drive is 40 times faster). Can hold up to 650 MB (megabytes) of data. Useful for the distribution of today’s large programs and information libraries, which you can then copy (all or in part) onto your hard disk. One of the safest forms of storage, provided that you don’t attack it with a sharp or heavy object and cannot be damaged by stray magnetic fields. CD-ROM drives cost under £20 and are now the minimum expected standard fitted to any computer.
Widely used by the music industry as they give better quality sound and do not stretch or wear out like audio cassette tape.
Record once CD-R and rewriteable CD-RW drives are now available for under £30. Cost of a blank CD disk is under £0.20. They have largely replaced both the standard floppy disk drive and the CD-ROM drive as the expected standard specification for most of today's computers.



x 1 = 451 x
Floppy disk



void(0);Digital Versatile Disk (-ROM) - also known as a Digital Video Disk is a very large capacity CD-ROM with similar access speed. It can store up to 4.7 GB (gigabytes) of data which is enough to store a feature-length film of 2-6 hours in length depending on the picture quality desired. A DVD drive can also read a normal CD disk and the so called 'combo' drives can also write to CD-RW disks. At a cost of under £50 they are now becoming the minimum standard, especially on laptops.
Rewriteable DVD-RW drives are currently around £50-100 and usually available as an optional extra. Disks are very cheap at around £0.20 for DVD-R and £0.40 for DVD-RW.
DVD recorders are now replacing the standard video cassette recorder for use in home recording.



x 1 = 7 x



- looks and is used just like a floppy disk but contains a rewriteable compact disk inside. With 100 megabytes capacity it is most suitable for the large picture files created on modern computers and for storing photographs in some older digital cameras. Now superseded by the memory stick in computers and memory cards in void(0);cameras as the latter require no moving parts to wear out.

- a short strip of magnetic tape for storing a small amount of data. The simplest type has a personal identity number (PIN) permanently stored on it, eg. credit card, cash-point card - used to withdraw cash from the Automatic Teller Machines (ATMs) on the walls of banks. Others can be written to as well, perhaps to store a running total, eg. phone card, debit card, library card.

void(0); - contains a processing microchip to provide it with intelligence as well as memory - it is really a tiny computer, eg. the SIMcard used in a mobile phone identifies you through a PIN number, identifies and connects to your service provider and provides a menu of options, as well as storing phone numbers and phone settings.

void(0); - a series of printed parallel black lines of varying thickness on a white background used to represent (and therefore store) a decimal number code. Almost everything you buy has a bar code either on it or on its packaging. A computer is used to print the bar codes which can later be scanned back into a computer very quickly. They can then be processed or translated into useful information for display, eg at a supermarket checkout or for creating a library database.

void(0); - a remote input/output device, which stores data received from sensors that can then be input into a computer at another time or place. It can be left alone to collect data over a long period of time and in hostile places, such as on a satellite, at the bottom of the ocean or at the South Pole.

void(0); - there are many chips inside a computer, some perform all the processing tasks (eg. the Intel Pentium CPU), and some are used for the storage of data as internal memory. They have the fastest access of all storage media. Because of this, all files read from the hard disk into memory are also copied into a separate memory "cache" and the next time you attempt to load them from the hard disk, the computer will look in the cache first. There are two types of internal memory:

(Read Only Memory) chips are used to store the permanent operating system data (the BIOS). In some types of computer, such as a pocket book, they may be used to store major programs such as a word processor. They are however more difficult to replace when a new version is released. They are also used to store the permanent programming inside a domestic device such as a television or washing machine.
(Random Access Memory) chips are used for temporary storage. They can be written to as well as read. A program and your work files have to be transferred from your hard disk into RAM when you want to work with them. You must then save your new work back onto the hard disk, as all RAM memory is lost when the computer is switched off. Computers today are normally sold with 16, 32, 64, 128 and 256 megabytes of RAM plus at least a 512KB cache RAM

void(0);USB Memory Stick or Pen Drive - The ultimate (and latest) replacement for the floppy disk as a means of mobile storage. High memory capacity on microchip therefore no moving parts and almost instant access. It plugs directly into the USB port on any computer. Costs: 128MB for £10-20, 256MB for £30 on up to around 4GB.
void(0);Memory Card - similar to the memory stick but designed to be used in devices such as portable music players, personal digital assistants, digital cameras, camcorders, mobile phones or PC’s. There are two types - SD (Secure Digital) and CF (Compact Flash). A 512MB card costs around £25-30

Bits and Bytes
A byte is the unit of memory representing one unit of data.
It is a code made up of 8 bits (binary digits).
For example 01100001 represents the lower case letter 'a'.
(Imagine 8 people standing in a row on the top of a hill at night, each holding a torch. 0 means 'off' and 1 means 'on'. As nothing else is possible for each torch only these two numbers are needed to represent the signal. This, in brief, is what we mean by 'digital' or more exactly 'binary digital'.)
A byte is the amount of memory needed to store one keyboard character.
1 kilobyte (KB) = 1000 bytes (10^3)
1 megabyte (MB) = a million bytes (1000 kilobytes) (10^6)
1 gigabyte (GB) = a billion bytes (1000 megabytes) (10^9
1 terabyte (TB) = 1000 gigabytes (10^12)
1 petabyte (PB) = 1000 terabytes (10^15)

  • About 4 kilobytes (4KB) is needed to store one full A4 page of text.
  • A ten volume encyclopaedia or 20 musical recordings might occupy 600 megabytes (600MB) on a CD-ROM.
  • A full-length feature film might occupy 4 gigabytes (4GB) on a DVD.
  • You would need something in the order of petabytes (billions of megabytes) to store all the data for a complete human being in an electronic state, either on a microchip to produce a hologram person such as "Rimmer" in "Red Dwarf" or for transporting as a beam of energy to another planet as in "Startrek".

Computer Network is a number of computers linked together to allow them to share resources. Networked computers can share hardware (such as a printer), software and data.
There are two types of network:
  • LAN - Local Area Network
  • WAN - Wide Area Network
A LAN is a Local Area Network covering a small area such as one building e.g. in a school or a college.

file server with three stations connected and a printer
file server with three stations connected and a printer

Within a LAN, computers and other hardware devices are connected to the file server. This allows the computers to share resources.
A WAN is a Wide Area Network covering a large geographical area.
host computer with terminals connected
host computer with terminals connected

Within a WAN, many terminals are connected to the host computers. This allows networks to be cover a large geographical area.
  • The Internet is a WAN.
  • A network of bank cash dispensers is a WAN.
  • A school network is a LAN.
  • LANs are often connected to WANs, for example a school network could be connected to the Internet.
Telephone lines are often used to connect WANs. LANs use dedicated cables or wireless technology.
  • Sharing devices such as printers saves money.
  • Site licences are likely to be cheaper than buying several stand-alone licences.
  • Files can easily be shared between users.
  • Network users can communicate by email.
  • Security is good - users cannot see other users' files unlike on stand-alone machines.
  • A file server is easy to back up as all the data is stored in one place.
  • Purchasing the network cabling and file servers can be expensive.
  • Managing a large network is complicated, requires training and a network manager usually needs to be employed.
  • If the file server breaks down the files on the file server become inaccessible. E-mail might still work if it is on a separate server. The computers can still be used as stand alones.
  • Viruses can spread to other computers throughout a computer network.
  • There is a danger of hacking, particularly with wide area networks. Security procedures are needed to prevent such abuse.

Data is numbers, words or pictures without context or meaning.
File server
A file server stores files centrally so that other computers on the same network can access them.


The act of accessing computer systems illegally.


A Local Area Network covering a small area such as one building eg in a school or a college.


A number of computers linked together to allow them to share resources.


A virus is programming code which spreads from computer to computer causing damage to the computer and/or software. A virus spreads by duplicating and attaching itself to other files.


A Wide Area Network covering a large geographical area.
Analogue is data that is changing all the time. Like a fotograph.
Digital is what a computer can understand like yes or no.

Modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from driven diodes to radio.
Hub is a device for connecting multiple twisted pair or fiber optic Ethernet devices together, making them act as a single network segment. Hubs work at the physical layer (layer 1) of the OSI model. The device is thus a form of multiport repeater. Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it detects a collision.
Analogue to digital converter is a device that converts contionues signals to discrete digital numbers.
The modem on a computer translates digital signals into an analogue 'noise', and transmits it down a telephone line.
You need to use your own words to answer questions!!!!
Dial-up Internet Access is a form of Internet access via telephone line.The user's computer or router uses an attached modem connected to a telephone line to dial into an Internet service provider's (ISP) node to establish a modem-to-modem link, which is then used to route Internet Protocol packets between the user's equipment and hosts on the Internet.
Advantages of a dial-up connection:
1. Low Price
2. Secure connection – your IP address continually changes
3. Offered in rural areas – you need a phone line
The main advantage you experience while using a dial-up connection is low price. You would expect to pay between $9.99 and $30 for dial-up Internet service, depending on the speed and functionality you desire. In addition, a dial-up connection is considered to be much safer and secure than a broadband connection. Each time you dial online, a unique IP address is assigned to your account. Since the IP address constantly revolves, it essentially makes your dial-up connection more secure and lessens the threats from hackers. Another distinct advantage a dial-up connection possesses is the availability of the service anywhere your phone service is offered. Dial-up service allows you to complete online training programs whether you live in a metropolitan city or in rural community.
Disadvantages of a dial-up connection:
1. Slow speed
2. Phone line is required
3. Busy signals of friends and family members
The main drawback using a dial-up connection for facilitating online training is the relatively slow speeds available to you (low bandwidth). The maximum speed your dial-up connection can achieve for online viewing is 56,000 bytes per second, better known as a 56K speed connection. The functionality of online training programs can suffer when you are interested in using applications such as Java or Shockwave. In addition, viewing streaming video, large email attachments or graphical images can become quite cumbersome with a low bandwidth connection. Another disadvantage you have when using a dial-up connection for online training is the necessity of having a landline. With the advent of cell phones and portable electronic devices, you may opt out of paying for landline phone service. With a dial-up connection, a landline is necessary for you to connect to the World Wide Web. Another drawback with using a dial-up connection is the busy signals friends or family may encounter when you are connected to the Internet. Your dial-up connection ties up the phone line, unless an extra phone line is purchased.
Dial-up connections are still considered to be the leading way of providing Internet service for customers around the country. However, with the advent of broadband services, dial-up connections may become an outdated technology for you to view online training programs. Many of the applications and programs necessary to operate your online training programs may not be able to be used in the future with a dial-up connection.

terabit per second
5.6 *10-08
gigabit per second
5.6 *10-05
megabit per second
kilobit per second
bit per second

Integrated Services Digital Network or Isolated Subscriber Digital Network (ISDN), originally "Integriertes Sprach- und Datennetz" is a telephone system network. Prior to the ISDN, the phone system was viewed as a way to transport voice, with some special services available for data. The key feature of the ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system. There are several kinds of access interfaces to the ISDN defined: Basic Rate Interface (BRI), Primary Rate Interface (PRI) and Broadband-ISDN (B-ISDN).
ISDN is a circuit-switched telephone network system, that also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better voice quality than an analog phone. It offers circuit-switched connections (for either voice or data), and packet-switched connections (for data), in increments of 64 kbit/s. Another major market application is Internet access, where ISDN typically provides a maximum of 128 kbit/s in both upstream and downstream directions (which can be considered to be broadband speed, since it exceeds the narrowband speeds of standard analog 56k telephone lines). ISDN B-channels can be bonded to achieve a greater data rate, typically 3 or 4 BRIs (6 to 8 64 kbit/s channels) are bonded.
  • No problems because of interferences
  • Max. download speed 64 kbps; using both lines 128 kbps
  • Max. upload speed 64 kbps; using both lines 128 kbps
  • Supported by all the providers
  • Proved technology
  • Two phone lines
  • An ISDN connection has to be installed
  • An ISDN adapter is necessary
terabit per second
6.4 *10-08
gigabit per second
6.4 *10-05
megabit per second
kilobit per second
bit per second

Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call. A splitter - or microfilter - allows a single telephone connection to be used for both ADSL service and voice calls at the same time. Because phone lines vary in quality and were not originally engineered with DSL in mind, it can generally only be used over short distances, typically less than 4km .
At the telephone exchange the line generally terminates at a DSLAM where another frequency splitter separates the voice band signal for the conventional phone network. Data carried by the ADSL is typically routed over the telephone company's data network and eventually reaches a conventional internet network. In the UK under British Telecom the data network in question is its ATM network which in turn sends it to its IP network IP Colossus.
Compared with dial-up internet, ASDL brpadband is much quicker; how much depends on which package you buy. Dial up downloads data at 56Kbps, that's 56 thousand bits of information per second. Compare that with the slowest broadband, not normally available anymore: 256Kbps and the standard/fast 2Mbps: 2 million bits per second. That's quite a lot faster! Another advantage is that broadband uses signals that do not disturb the normal phone signals, so you can use a telephone at the same time as accessing the internet. One more, is that broadband is, in general, an 'always on' connection which means that it is always connected and ready to go. Because of this, broadband is billed either as a flat rate, or by the amount of data that you download rather than by the time connected as many dial-up providers use.

terabit per second

8 *10-06
gigabit per second

megabit per second

kilobit per second

bit per second


Computer Networks

Advantages Disadvantages

Share resources, Printers, files… Rely on servers / goes down.
Communicate. You need special H/W, hub, switches, cabling
Software, common. Viruses can spread easily.
Restrict access. Specialized staff, cost money
Easily backup.
Centralized data.
Peer to peer Networks

Comps. Are of equal importance data s/w is stored locally.

Client/Server Networks

Data + sw sometimes is stored in sever access is controlled by server or servers. (Usernames +Passwords), login id.

1. The manager of a small business is thinking that intalling a network so that the different departments can share data. He has been told that it would be best to use a star network topology.State the advantages and the disadvantages of using that type of network? Advantage
  • Better performance: Passing of Data Packet through unnecessary nodes is prevented by this topology. At most 3 devices and 2 links are involved in any communication between any two devices which are part of this topology. This topology induces a huge overhead on the central hub, however if the central hub has adequate capacity, then very high network utilization by one device in the network does not affect the other devices in the network.
  • Isolation of devices: Each device is inherently isolated by the link that connects it to the hub. This makes the isolation of the individual devices fairly straightforward, and amounts to disconnecting the device from the hub. This isolated nature also prevents any non-centralized failure to affect the network.
  • Benefits from centralization: As the central hub is the bottleneck, increasing capacity of the central hub or adding additional devices to the star, can help scale the network very easily. The central nature also allows the inspection traffic through the network. This can help analyze all the traffic in the network and determine suspicious behavior.
  • Simplicity: The topology is easy to understand, establish, and navigate. The simple topology obviates the need for complex routing or message passing protocols. As noted earlier, the isolation and centralization simplifies fault detection, as each link or device can be probed individually.


The primary disadvantage of a star topology is the high dependence of the system on the functioning of the central hub. While the failure of an individual link only results in the isolation of a single node, the failure of the central hub renders the network inoperable, immediately isolating all nodes. The performance and scalability of the network also depend on the capabilities of the hub. Network size is limited by the number of connections that can be made to the hub, and performance for the entire network is capped by its throughput. While in theory traffic between the hub and a node is isolated from other nodes on the network, other nodes may see a performance drop if traffic to another node occupies a significant portion of the central node's processing capability or throughput. Furthermore, wiring up of the system can be very complex. 2. a) Explain why it is important to restrict users acesss to a computer network.
Security is one of your most important tasks as a network administrator. You need to make sure that users are who they say they are and that they have proper access to the network. However, try as you might to set up security policies on your network, users may attempt to find ways around them. In this TechProGuild Daily Drill Down, I’ll show you how you can use NDS to enforce the restrictions and policies you have on your network.
b) How do you restrict acess to a computer network.
To create the registry key to restrict access to the registry:
  1. Start Registry Editor (Regedt32.exe) and go to the following subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control
  2. On the Edit menu, click Add Key.
  3. Enter the following values: Key Name: SecurePipeServers
    Class: REG_SZ
  4. Go to the following subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurePipeServers
  5. On the Edit menu, click Add Key.
  6. Enter the following values: Key Name: winreg
    Class: REG_SZ
  7. Go to the following subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurePipeServers\winreg
  8. On the Edit menu, click Add Value.
  9. Enter the following values: Value Name: Description
    Data Type: REG_SZ
    String: Registry Server
  10. Go to the following subkey.HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurePipeServers\winreg
  11. Select "winreg". Click Security and then click Permissions. Add users or groups to which you want to grant access.
  12. Exit Registry Editor and restart Windows.
  13. If you at a later stage want to change the list of users that can access the registry, repeat steps 10-12.

I'd like you to use your own words, and not copy of a website, plus why do you complicate yourself so much? Star topology advantage: Each node has a line to the network for itself. and if a node fails the rest still work Disadvantage: If the hub fails all the nodes attached to that hub will not be able to operate on the network.

Restrict access to users so they only use what they're allowed to use i.e. administration, teachers, students, students aren't allowed to see teachers files, but teachers are allowed to see the students files.

You use usernames and passwords to restrict access.


page 27.

1. List three things that can be shared using a computer network.
Files, Resources and Programs.
2. Explain what is meant by LAN, WAN, topology, node and file server.
LAN is local area network;WAN is wide area network; topology is the studie of the arrangement of a network; node is an active electronic device that is attached to a network, and is capable of sending, receiving, or forwarding information over a communications channel; File server is a high-performance computer containing large hard-disk drives that are available to all network users;

page 29.

1. Give two reasons why wireless technology is becoming more popular.
Because as a way to transmit Internet data to WAP mobile phones.
2. List two advantages and two disadvantages of using a networked computer.
Advantages: Acces to network from any workstation, Share files with, and send messages to, other computers.
Disadvantages: hackers, viruses
3. List six services provided by the Internet.
E-mail, World Wide Web, Newsgroups, Internet relay chat,Private communities,File transfer protocol.
4. Explain why the Internet is called ´a network of networks`.
Because it connects over 50 million computers worlwide. The Internet was strarted in 1969 in the USA to link up centres in the event of nuclear attack. Gradually, more networks joined, connecting thousands of commercial, goverment and educational networks.

5. List three things needed for a user to acess the internet.
Needs a modem, software and an Internet service provider.

Number 1 ??? Number 2, missing dissadvantages
Definitions ???

Intranet: is a private network based on Internet standards but only available within a business or other organisation.
Firewall: is computer software that stops computers on other networks, including the Internet, accessing an intranet.
Gateway: is computer hardware that lets a particular network to join with another network.
EDI: is electronic data interchange this is how we can exchange data.
Extranet: allows authorised outsiders limited access to an intranet.
Encryption: EDI often involves putting the data into special computer code to stop other people looking at the data.
E-Commerce: is the term used for the buying and selling of goods and services on the Internet and, in particular, the World Wide Web.

what does defitions mean?

A user: is a person that uses a computer.
A user network: is a person that uses a computer network.
Viruses, hackers can occur.
If hardware fails you can be disconnected from the network.
If a server fails you can not share things.
You can put an antivirus to prevent viruses.
Usernames - to provide each user with their own area on the hard disk to store work; to restrict access to the rest of the system; to prevent them from deleting or installing programs and other files; to prevent them from changing the way the computer is set up.
Passwords - a secret combination of letters and/or numbers known only to the user to protect their own work files from tampering by other users. Similarly, cash-point cards have a personal identity number (PIN) to prevent other people using the card. There is usually a restriction on the number of attempts allowed.
Modems - should be disconnected either from the computer or from the telephone line when not being used. This is the only way in for external hackers.
Backup copies - Work files can be lost or damaged by system faults, malicious damage or by the user making mistakes. Multiple copies should be kept, by saving at significant stages in the development of the work, using sequentially named files. They should be backed up at the end of the work session by making copies onto a floppy disk. Really sensitive work could then be deleted from the hard disk. The floppy disk can be taken away and kept securely by the owner in a safe place. Files on a network server should be backed up onto a tape every night - normally a separate tape for each day of the week so that there is more than one current copy.
Floppy disks - The write-protection hole in the corner of the floppy disk should be kept covered to prevent accidental wiping of the disk or the introduction of viruses. The disk must be kept clean, dry and away from magnetic fields or places where it might be physically damaged.
Malicious Software - these are computer programs written by very clever but misguided, destructive people. (This should not be confused with software bugs which are mistakes or errors in a program that might cause it to crash unexpectedly - nothing's perfect!).
There are three main categories of malicious software:
Computer viruses - act in a similar way to living viruses (which take over the cells of a host organism and change their behaviour). Once introduced into a computer, via a floppy disk, email or the Internet, a virus will attach itself to a system file or program. It then reproduces and spreads to other programs on your hard disk and eventually onto all of your floppy disks. They can alter the host program to make it do strange things or to stop it working completely, some can cause the whole hard disk to become scrambled. Also, as with living viruses, they can wait quietly for months or even years until certain conditions occur before they act - the "Friday the 13th" and "AIDS" viruses being obvious examples. They can also disguise and mutate themselves so that it becomes difficult for anti-virus software to detect and destroy them.

Computer worms are small programs that reproduce rapidly and spread throughout the system (just like intestinal worms). Unlike viruses, they do not infect actual programs but simply do undesirable things by themselves and fill up the hard disk until there is no space left for the computer to use. A whole network system will slow down and eventually stop working if its server's hard disk becomes infected.
A Trojan Horse, (like the one used to attack the Greek city of Troy) is a program that pretends to be something it is not. It will load instead of the expected program and do something unwanted, like sending your password or bank account details to someone, before loading the real program. The unsuspecting user may not know what is happening, before it is too late. Unlike viruses and worms, Trojans do not reproduce themselves.
Methods of protection:
  • Never use a floppy disk given to you from an untrustworthy source or pass floppy disks around between your friends.
  • Never start up a computer with a floppy disk left in the drive.
  • Keep the write-protection hole covered on floppy disks that are used to store original "clean" programs - so they can be reinstalled with confidence.
  • Never open an email attachment that comes from someone unknown or is not clearly explained in the email message.
  • Install a virus protection program on your hard disk - this will detect known viruses and typical virus activities. It may also "inoculate" programs so that any changes can be detected as soon as they occur. If the virus is a known one it may be removed from the file, otherwise the infected file is "quarantined" for deletion before the virus can spread.
Hardware security - protecting the computer itself by locks on doors and windows to the room; using security bolts to fix the computer permanently to the desktop; removing the keyboard and locking it away in a cupboard at night or using the lock and key provided on most modern computers.
The Data Protection Act - became law in July 1984 to prevent personal information stored on computer from being made freely available to anyone anywhere in the world. You also have the right to see such information and have any errors corrected. The act does not apply to data related to national security, crime detection, immigration, salaries and income tax.
Hacking - is the attempt by an unauthorised person to obtain entry into a computer system in order to interfere with the programs or data that are stored there. This is illegal and can result in a heavy fine and prison sentence. To reduce the chances of this happening the following measures should be taken:
  • change passwords regularly, using passwords with at least six characters and that have no meaning which would make them easy to guess.
  • have an automatic lockout if a password is wrongly entered more than three times. This will prevent access by password guessing software.
  • disconnect a modem if the computer system is left on and unused overnight.


A security network is how to protect our network from hackers, Trojan Hourses, Computer worms, Computer viruses and Malicious Software. We can use The Data Protection Act, Hardware security, Backup copies, Modems, Passwords, Usernames.

====== Tus cambios
======Computer Networks
A network consists of a number of computers linked together. (interconnected with each other)

Analogue data is data which changes continuously, e.g a photo, a telephone conversation and a dimmer switch.
Digital data is data made up of binary information 0s and 1s, e.g computer information and a light switch.

You can connect to the internet in different ways
1. Dial up
2. Uising ISDN
3. Using ADSL
The internet is a giant network of computer networks.
LAN: local area network

Computer Networks
a) Describe a modem and its purpose;
A modem is a device that makes signals to encode digital information or to decode transmitted information. Communicate through telephone lines.
b) State the difference between analogue data and digital data;
The difference between analogue and digital data is that analogue data is data which changes continuously, e.g. a photo, a telephone conversation and a dimmer switch and digital data is data made up of binary information 0s and 1s, e.g. computer information and a light switch.
c) Explain the need for conversion between analogue and digital data;
So computers can be with ral data. So computers can understand and work with real world data like for example temperature body temperature.
d) Identify the advantages and disadvantages of using common network environments such as the Internet;
Advantages: Access to network from any workstation, Share files with, and sends messages to, other computers.
Disadvantages: hackers, viruses, malicious software, computer worms.
e) Describe what is meant by the terms user and password, stating their purpose and use;
A user: is a person that uses a computer or internet service. A password is a secret word for you to enter your account. We need this for interacting with others. And have a social life. To protect our documents programs.
f) Identify a variety of methods of communication such as fax, e-mail, bulletin boards, and Tele/video conferencing;
Theres different types of communication telephone, radio, television.
g) Define the terms Local Area Network (LAN), Wireless local area network and Wide Areatelevision Network (WAN);
LAN: Is when a computer printer and large hard disks usully on site can be linked a local area network.

WAN: many small and large computers, located in different sites spread over a large geographic area or different countries, can be linked in a wide area network.

h) Describe the difference between LANs WLANs and WANs, identifying their main characteristics;
LAN: Is when a computer printer and large hard disks usully on site can be linked a local area network.

WAN: many small and large computers, located in different sites spread over a large geographic area or different countries, can be linked in a wide area network.

i) Identify the different network topologies (including star, ring, bus and hybrid)
There are three types of network topologies: physical topologies, signal topologies, logical topologies. Inside this three categories there is Bus, Star, Ring, Mesh, Tree, Point-to-point. In your own words please, and talk about them
j) Describe the characteristics and purpose of common network environments, such as intranets and the Internet; Intranets and extranets (what are they?) may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet. k) Describe common network devices (including hubs, routers, bridges, switches and proxy servers)
All networks are made up of basic hardware building blocks to interconnect network nodes, such as Network Interface Cards (NICs), Bridges, Hubs, Switches, and Routers. In addition, some method of connecting these building blocks is required, usually in the form of galvanic cable (most commonly Category 5 cable). Less common are microwave links (as in IEEE 802.12) or optical cable ("optical fiber"). An ethernet card may also be required. In your own words please,
l) Discuss the problems of confidentiality and security of data, including problems surrounding common network environments;
The problems of confidentiality and security of data are that there´s decreasing the security and confidencially because jackers are entering the network environment. m) Identify the need for encryption and authentication techniques including user identification and passwords, when using common network environments such as the Internet.

We need to have identification and passwords to have a privacite and security and confidentialy of our things. And username/passwords help us because...

You have a lot of work to do! 4/10

Use the words below just once in order to fill in the gaps
computer network
local area network (LAN)
user name
wide area network (WAN)
file server
work station

A computer network is a collection of computers that have been linked together so that

they can communicate with each other. This enables them to share files,

data and hardware .

Computers in a network are joined together by cables or radio waves. This allows the data to move between each computer. Computers that are located in the same building or fairly close together are usually connected to form a Local area network (LAN). Computers that are a long distance apart, in a different town or country are networked to form a Wide area network (WAN).
A work station is sometimes used. This is a powerful computer that can store many files or programs. This often controls the other computers and allows users to access their software from any machine on the network. It also allows users to share files with one another.
In order to log onto a computer network, you need user name and a password.
A single computer on a network is known as a file server.


Use the mini-website to help you complete this task:

The speed of transferring files and information is very rapid.

Server faults stop applications being available.

The cost is very low

Resources could be located too far from users.

The are usernames and passwords for our security in school.

User work dependent upon network

Software can be loaded on one computer eliminating that need to spend time and energy installing updates and tracking files on independent computer throughout the building.

Network faults could lead to loss of resources.

E-mail aids in personal and professional communication. Electronic mail on a LAN can enable staff to communicate within the building having to leave there desk.

System opens to hackers.

Resources such as, printer, fax machines and modems can be shared.

Decisions tend to become centralised.


Explain in your own words why you need both a user name and a password. Describe the purpose of each.

We neeed both user name and password to have so kind of security and privasity of for example a notebook or anything that we don´t want other people to see. The purpose of the two is that they give us the privasity we need and no one expect us knows what is in and the username and password.

Draw a labelled diagram for each network topology, in the table below. You need to also think about some advantages and disadvantages for each. Think about things like:
· What would happen if a cable broke?
· How much cable do you need?
· Can data collide with each other?
· Which is the fastest?


Bus  network topology indicated with server, connected terminals and network printer.
Bus network topology indicated with server, connected terminals and network printer.



· Cable faults are easily identified.

· Cost effective as only a single cable is used.


· Limited cable length and number of stations.

· It is slower than the other topologies.


Ring network topology indicated with server, connected terminals and network printer.
Ring network topology indicated with server, connected terminals and network printer.


· Performs better than a star topology under heavy network load.
. Does not require network server to manage the connectivity between the computers.

· Moves, adds and changes of devices can affect the network.
. Much slower than an Ethernet network under normal load


Star network topology indicated with server, connected terminals and network printer.
Star network topology indicated with server, connected terminals and network printer.


. The topology is easy to understand, establish, and navigate. The simple topology obviates the need for complex routing or message passing protocols. As noted earlier, the isolation and centralization simplifies fault detection, as each link or device can be probed individually.

. Each device is inherently isolated by the link that connects it to the hub. This makes the isolation of the individual devices fairly straightforward, and amounts to disconnecting the device from the hub. This isolated nature also prevents any non-centralized failure to affect the network.
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