[NCBI_ECDL_class] mod 1 notes
- From: "Joe Lonergan" <joelonergan25@xxxxxxxxxx>
- To: <ncbi_ecdl_class@xxxxxxxxxxxxx>
- Date: Wed, 9 Jun 2010 23:44:17 +0100
Hi folks
notes are attached as well as below.
Hardware
Hardware is any part of the computer that you can physically touch, pick up,
hold,
move around the room etc.
Examples of hardware include the monitor, mouse, hard disk, motherboard etc.
3. Software
Software are the applications and programming instructions needed to make the
computer hardware do useful work.
Some examples of systems software which tells the computer what to do:
a.. Operating System
b.. Utilities
c.. User Interface
Some examples of application software which allow you to do your work:
a.. Word processors such as Microsoft Word
b.. Spreadsheets such as Microsoft Excel
c.. Databases such as Microsoft Access
Peripherals
A peripheral is any hardware device which connects to the computer and is
controlled by the Central Processing Unit CPU -with the exception of memory.
When you are trying to think of examples of peripherals, think of things which
plug into the back of the box.
Examples are:
a.. monitor
b.. keyboard
c.. mouse
d.. printer
e.. scanner
f.. speakers
g.. external hard drives
Bits and Bytes
When you are using a computer you are probably opening documents, sending
emails, checking web pages etc. All of these items are made up of data.
Your computer needs to be able to read this data so that it can respond to your
requests e.g. making a word bold, sending a document to print.
But, the computer doesn't understand the words on the page. It can only deal
with binary data - yes, you knew those maths lessons would come in useful some
time!
Binary data consists of just two values, 0 and 1.
So, the smallest piece of data that can be stored is called a 'bit' and that is
either a 0 or a 1. The term 'bit' comes from 'binary digit'
However, a bit is just that weeny bit too small for even the computer to deal
with. So, it usually deals with 8 bits at a time.
8 bits of data are called a 'byte'
One keyboard letter, for example, 'a' or 'd' is one byte in size. So a page
which contains 100 letters would be 100 bytes in size.
Storage Sizes
You now know the terms 'bit' and 'byte'
However, we normally refer to the capacity of a storage device in terms of:
Kilobytes (KB)
Megabytes (MB)
Gigabytes (GB)
or even Terabytes!
Storage sizes
Quantity
Information
Bit
Smallest unit of data, either a 0 or 1
Byte
8 bits
Kilobyte (Kb)
Assumed to be 1,000 bytes. In reality, it is really 1,024 bytes - this is
the number you must remember for your test.
Megabyte (Mb)
1,024 Kb
Gigabyte (Gb)
1,024 Mb
You need to know the size order of the different storage units and how they
compare to one another.
If you have trouble remembering the order, Judy McAlinden kindly sent us this
mnemonic to help you out:
Blooming (bit)
Belle (Byte)
Killed the (Kilobyte)
Mad (Megabyte)
Gabby (Gigabyte)
Teacher (Terabyte)
7. Document Sizes
Here are some examples of different document sizes -you don't need to learn
these. They are just here to help you put the different storage sizes into
context.
Document sizes
Document
Approximate size
Short email
5 - 10 Kilobytes
Business Letter
25 Kilobytes
Medium sized report
100 Kilobytes
Web page with images
150 Kilobytes
A three minute song
3 - 5 Megabytes
In the previous section you learned the meaning of terms like 'hardware',
'software' and 'peripherals'.
You also found out about the different sizes of data storage units.
This next section will introduce you to the different types of computer
available today.
You don't need in-depth knowlege but you do need to know which are suitable for
certain circumstances, which are the most powerful and which are the fastest.
Super computers
Supercomputers are the fastest and most expensive computers in the World.
They can cost over a hundred million pounds to build and very few organisations
can afford to purchase one.
They are mainly used by organisations such as:
- Large universities who do a lot of research projects such as scientific
research
- Meterological Office to model weather conditions so that weather forcasts can
be developed
- Pharmaceutical companies for drug research
- The military for weapons research.
Whilst supercomputers are working, they generate so much heat that they need to
be housed in specifically designed rooms with environmental controls and air
conditioning systems.
Mainframe
Mainframes are large, powerful computers that can carry out many different
tasks for many different people at the same time.
They are slower than a supercomputer but they are far less expensive. They may
cost around 4 million pounds to purchase.
Mainframes can execute billions of instructions per second and can process
large amounts of data simultaneously.
They are usually connected to a large number of peripherals e.g. printers,
terminals, disk drives etc.
They are used by large companies such as:
a.. Utility companies e.g. gas and electricity suppliers to calculate
customer bills.
b.. Banks - for managing thousands of customers accounts each day
c.. Insurance companies - for keeping track of policies and claims
d.. Airlines - for dealing with bookings, tickets, cancellations etc
e.. Police - for storing and processing all of the data collected each day
about crimes
Mainframe computers need to be operated by specialist, trained staff. They are
usually kept in an air-conditioned rooms away from the office or factory floor.
Network Computer (Server)
A server is a networked computer that is providing a specific service to other
computers on the network.
For example:
a.. File server. Users store files on the network file server. Users can do
all the usual file functions - copy, delete, change, duplicate by sending
commands to the file server.
a.. Print server - on larger networks there is often a computer whose sole
task is to manage printing jobs sent to a networked printer. This machine is
called the print server. Printing in this way frees up the user computer to do
other things.
Other services may include handling video files or perhaps music files.
Servers are often more powerful than normal desktop computers because they need
to be able to administer a network of possibly hundreds or thousands of
computers. They also need to be able to maintain the security of the network.
Personal Computer
In the early days (1980s) these types of machine were called micro-computers,
for example, schools often had a BBC micro-computer. But now we tend to call
them 'desktop personal computers' or just 'PC'.
The desktop PC has a central processing unit housed in a metal or plastic case
(often called a tower unit). A keyboard and mouse are usually used to input
data and a monitor to output the data.
Modern PCs are quite powerful. They can carry out millions of calculations per
second. However, they are no-where near as powerful as a mainframe.
They are useful for lots of different types of tasks:
a.. Running office applications such as word processors, spreadsheets and
databases
b.. For CAD design such as designing kitchens
c.. Editing videos
d.. Creating and playing music
e.. Accessing the Internet for research, work and entertainment
Laptop
Laptops are small, portable computers which are used to work in confined spaces
or whilst you are on the move. Their popularity has increased with the
development of wireless networking which means that they can be logged into the
home or company network even when the user is not at their desk.
Laptops can be as powerful as desktop computers but you tend to pay more for
the same specification.
They can run the same software, they have the same functionality as desktop
computers.
Their main limitation is battery life. Although a lot of work has been done to
extend battery life, if it runs out while you are using the laptop, you have to
stop work until it can be recharged or you can find a mains socket.
Palmtop / PDA
Personal Digital Assistants (PDA) were originally developed as an electronic
organiser. They aimed to replace diaries, 'to do' lists and address books.
However, rapid development has resulted in palm tops and PDAs becoming almost
cut down computers in their own right.
PDAs are now available with cut down versions of the main Office software, e.g.
Microsoft Word, Excel and Access. The reason they are so successful is that
they usually have the ability to synchronize with a desktop PC. So, any work
you have been doing on your PDA can be uploaded to your PC and the files
updated.
Many PDAs can now also access the Internet and can be used to research web
pages, send emails or even play games. Some even double up as phones.
Palmtops are very similar to PDAs in their use. The main difference is that
Palmtops have a built in keyboard.
This next section will introduce you to the different types of memory and
storage devices that you need to know about.
You don't need in-depth knowlege of each method of storing data or instructions
but you do need to be able to make comparsions between them and also to choose
the
most appropriate one for a specific task.
System Memory (ROM)
Read Only Memory (ROM)
ROM is a special kind of memory which stores the instructions which the
computer uses when it 'boots up' - the BIOS (basic input output system).
It allows the computer to check the type of hard disk installed, the amount of
RAM installed (see next page), the type of CPU being used etc (previous page).
Because the data is 'read only', it can be read but not changed by the user.
The key thing to remember about ROM is that the data is not erased when the
computer is switched off - the data is stored permenantly, so it is called 'non
volatile memory'
3. Short Term Memory (RAM)
Random Access Memory (RAM)
How many times have you worked for a whole lesson on something which you were
just about to save but then the computer crashed or your mate 'accidentally'
switched it off. When you rebooted and logged back in, your work was gone
forever.
This was because your work was stored in RAM, or 'temporary memory'. It was
fairly safe there while the computer was working, but as soon as it was
switched off, everything disappeared. This type of memory known as 'volatile
memory'.
Most computers are typically sold with 512Mb - 2 Gb of RAM installed.
Long Term Storage - Hard Disk
The hard disk is the main long term storage device in your computer.
It is a bit like a filing cabinet: all of your data files and applications
software are stored on it.
Hard disks are measured in Gigabytes. A typical hard disk size will be around
120 Gb.
Hard disks are 'magnetic' storage devices.
It is possible to also have an external hard disk which can be plugged into the
computer and used to back up your data and then stored in a different place to
keep it safe.
Advantages
a.. necessary to support the way your computer works
b.. large storage capacity
c.. stores and retrieves data much faster than a floppy disk or CD/DVD
d.. Stored items are not lost when you switch off the computer
e.. Cheap on a cost per megabyte compared to other storage devices
Disadvantages
a.. Far slower to access data than ROM or RAM chips
b.. Hard disks can crash which stop the computer from working
c.. Regular crashes can damage the surface of the disk, leading to loss of
data in that sector
d.. The disk is fixed inside the computer and cannot easily be transferred to
another computer.
5. Removable Storage - Floppy Disk
Floppy disks are one of the oldest types of portable storage devices still in
use, having been around since the 1980s. However, they are gradually becoming
obsolete and some manufacturers are now starting to build their PCs without
floppy disk drives.
A floppy disk can store up to 1.44 Mb of data which is equivalent to around 300
pages of A4 text.
They used to be the ideal storage device for transferring small files from home
to work/school or from one office computer to another. But nowdays, many files
contain graphics or WordArt and are larger than the size of the floppy disk.
Floppy disks are a magnetic storage device.
Formatting a disk
All disks must be formatted before data can be written to the disk. Formatting
divides the disk up into sections or sectors onto which data files are stored.
In the past, the user would have to format their own disks, but now they are
sold pre-formatted.
Storage - Zip Disk
Zip disks are pretty much obselete now. However, they were very popular as a
backup medium before CD-RWs were developed and became cheap enough for everyone
to use.
Zip disks look similar to a floppy disk but are a little bit thicker.
Computers generally didn't come with a zip drive installed, so you couldn't
just use one in the same way as a floppy disk. You needed a seperate plug in
drive, which was an extra expense.
They can store around 100Mb of data - 70 times more than a floppy disk.
Challenge see if you can find out one extra fact on this topic that we haven't
already told you
Click on this link: Zip Disk
Advantages
a.. Stores more data than a floppy disk
b.. Compresses data, reducing the file size, so more data can be stored
c.. Portable
Disadvantages
a.. Almost obselete now
b.. Need a seperate zip drive to read the disk
c.. More expensive than floppy disks
d.. Fairly slow to access the data
Removable Storage - Magnetic Tape
The amount of work that you do on your computer at home can easily be backed up
onto a CD-RW or a memory stick.
However, many organisations, such as your school or an office, need to back up
large volumes of data each day. A CD-RW, DVD-RW or flash memory sticks just
would not be large enough for doing this.
Large organisations who need to back up their systems daily tend to use
magnetic tapes to store their data.
Magnetic tape uses 'serial access' to find a piece of data. It works in much
the same way as a video tape that you might have at home.
To find a specific piece of data, you have to start at the beginning of the
tape and continue fast forwarding until you get to the piece of data that you
need. This makes it fairly slow to find and retrieve data so it would not be
much use to store data that you needed to get hold of quickly.
Advantages
a.. relatively cheap per megabyte of storage
b.. can store large amounts of data - over 100 Gb
c.. can be set up to do the back up overnight or over the weekend
Disadvantages
a.. serial access so can be quite slow to access data
b.. need a special piece of equipment to record and read the data on the tape
Removable Storage - Compact Disks
Compact Disks come in three main forms:
CD-ROM - CD Read Only Memory. This means that when you buy the disk, it already
has the data or program stored on it. You can read it, but can't save to it. An
example would be a music CD that you buy from a shop.
CD-WORM - CD Write Once Read Many. This means that you are able to save to this
disk one time, so you can store your data or an application on it of your
choice. However, once you have saved onto the disk once, you can access the
data many times but can't save onto it again.
CD-RW - CD Read Write. This means that you can save data to your disk over and
over again, just like you can with a floppy disk.
Compact disks are known as optical storage devices. Data is burned onto the
surface of the disk using a laser beam in the CD drive. A laser beam is also
used to read the data stored on the disk.
A typical CD can store around 650 Mb of data - equivalent to 450 floppy disks.
The entire contents of four text based encyclopedias (no images) could be
stored on a single CD.
Removable Storage - DVDs
Digital Versatile Disks (DVDs) are amongst the most common methods of copying
and backing up data at home.
A DVD is similar to a CD in that it is an optical device and that a laser is
used to store the data and read the data.
A single sided DVD can store about 4.7Gb of data. DVDs which store data on both
sides can hold over 9Gb of data.
Advantages
a.. Very large storage capacity
b.. Sound and picture quality is excellent, making them ideal for storing
films with video and sound.
c.. DVDs are now mass produced so they are relatively cheap
d.. DVD players can read CDs
Disadvantages
a.. DVDs do not work in CD drives
b.. There is no single standard of DVD
c.. They can be easily damaged by breaking or scratching
Flash Memory
Flash memory storage devices are typically small, lightweight, removable and
rewritable. They consist of a small printed circuit board which is encased in
plastic or metal casing. They usually have a removable cap which covers and
protects the part of the stick which is inserted into a USB port.
Memory sticks are available from 1Gb up to 8 Gb.
Advantages
a.. They are more compact and portable than floppy disks or CDs/DVDs.
b.. They hold more data than a floppy disk and nowadays often more than a CD.
c.. They are more reliable than a floppy disk because they have no moving
parts
d.. They are being developed with fashionable looking outer casings and are
almost becoming a 'fashion accessory' much in the way of a mobile phone.
Disadvantages
a.. At the moment, the cost per megabyte of storage is more expensive than
floppy disks, CDs or DVDs.
b.. They can be easily lost
c.. The metal part which is inserted into the USB port can be snapped off if
they are handled roughly
Storage Device Comparison
Size / Capacity Comparison
Storage Device
Approximate size
Floppy Disk
1.44 Mb (smallest capacity)
Zip Disk
100 Mb
CD
650 Mb
Flash memory
1 Gb - 8 Gb
DVD
4.7 Gb
Magnetic Tape
Over 100 Gb
Hard Disk
Around 120 Gb - 1 Terabyte (largest capacity)
Speed of access to data
Storage Device
Order of speed of access to data
RAM and ROM
Fastest
Hard Disk
Flash Memory Stick
DVD / CD
Zip Disk
Floppy Disk
Magnetic Tape
Slowest
Cost per Gigabyte of storage
Storage Device
Order of cost per gigabyte
Magnetic Tape
Cheapest
Hard Disk
DVD / CD
Flash Memory Stick
Zip Disk
Floppy Disk
Most expensive
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