Chapter 2

• This presentation covers:

– Choosing input devices

– Choosing output devices

– Choosing storage devices

• There are 3 main types of keyboard:– QWERTY (the most popular)

– Alphabetical

– Dvorak

• Keyboards are useful for inputting small amounts of data.

• If you were asked to record large amounts of data then a keyboard probably isn’t the most suitable:– Mistakes are often made– There are more efficient tools you could use

• Concept keyboards allow you to create your own keys.

• A sheet or overlay is placed over a pad.

• Software is used to program the positions of your keys and assign values to them.

• You will often find concept keyboards in super markets and fast food restaurants.– Next time you are in a shop or a petrol station take a look

at the keyboard they use.

• There are many types of pointing device.

• The most common being a mouse.

• Some use a roller ball to track movement whilst others use optical sensors.

• Either way, a mouse needs a surface to operate on.

• If space is limited then sometimes touch pads, joysticks or tracker balls are used.

• Scanners translate information into a format that computers can understand.

• There are many forms:– Barcode– Optical Mark Reader (OMR)– Magnetic Card Reader– Flatbed Scanners– Magnetic Ink Character Recognition (MICR)

• It is very difficult to draw images on a computer using a mouse.

• We have been taught to draw holding a pencil or a paint brush.

• Graphic tablets provide a surface on which a user can draw directly into a system.

• The tablet picks up movements on the pad and translates them to the screen.

• Essentially, any device which converts an analogue signal to a digital one:– Digital Camera– Scanner– Graphics tablet– Vinyl to MP3 dock

• There are many types of input devices which have not been covered:– Digital Camera– Touch Screen– Microphone– Switch– Sensor

Research these devices and focus on their purpose and ergonomic features.

• Investigate the use of biometric devices as input devices. Describe the device and list their advantages and disadvantages. Give examples of where they might be used.

• Why are keyboards not suitable for inputting large amounts of data?

• What are the advantages of concept keyboards?

• Describe a digitiser.

• Describe two different types of scanner and give examples of where they should be used.

• What is the most efficient input device for a newspaper reporter and why?

• You are more than likely using a monitor to look at this presentation.

• Some people may have a print out of it and others may be viewing it through a projector.

• These are just some ways that the information in this presentation can be outputted to a user.

• Blind users may have the information read out to them using a screen reader.

• A monitor can come in different sizes and each type has it’s own benefits and negatives.

• Larger monitors tend to have higher resolutions (the number of pixels on a screen).

• The more pixels a monitor can display the more a user can see.

• Printers produce hard copy output.

• Three types of printer which are useful to know about include:– Dot Matrix– Ink Jet– Laser

• These are known as impact printers.

• An ink ribbon would be placed in front of paper.

• Little hammers hit the ribbon onto the paper which causes ink to transfer across.

• Quality tends to be poor but the advantage is that you can use carbon copy paper to make multiple copies of a document.

• They are often used for invoices and shop receipts.

• Ink jet printers squirt ink at the paper.

• They are quite cheap to run as the only part which needs replacing is the ink cartridge.

• The quality is better than dot matrix but they use more ink than laser printers.

• They are cheaper to buy than laser printers but cost more in the long run.

• These are high resolution printers that are very cost effective over time.

• They work through a process of firing laser beams at a rotating drum which creates an electrical charge which in turn attracts the toner onto the drum.

• Charged paper is then passed around the drum which transfers the toner to the paper.

• Heat is then applied to set the toner.

• Complete the following table:

• There are other types of printer. Research the following types:– Daisy wheel– Line– Thermal

Printer Description Advantages Disadvantages

Dot-Matrix

Ink-Jet

Laser

• You should consider the following:

– How much output?• What speed is needed• Is heavy-duty equipment needed

– Quality of output needed?• Letter quality• Near Letter quality• Draft

– Location of printer?• Is noise level important• How much space do you have?

– Multiple copies needed?

– Colour print required?

• There are two types of plotter to know about:

• Flat bed:– The paper lies flat and a pen moves across it in

multiple directions.

• Drum plotter:– Paper is stored as a roll of paper. As it unrolls a

pen moves across it at right angles.

• Research into the following output devices:– Loud Speaker– Lights

For each, describe their purpose and provide and provide a suitable example of their use.

• Research how a modem can be both an input and an output device.

• Describe three criteria you should consider when buying a printer.

• Identify two differences between a dot matrix and a laser printer.

• Describe a monitor.

• Describe two different types of plotter, noting the advantages and disadvantages of each.

• Who might use the following device and how might they use them:– 24” monitor– Flat-bed plotter– Colour laser printer– Loudspeaker

• Is a CD-writer an output device? Give reasons for your view.

• Storage devices are used to store data an programs.

• They are permanent forms of storage for data unlike RAM which doesn’t save data once a system is powered down.– Volatile memory – data is not kept permanently– Non-volatile memory – data is kept permanently.

• Storage capacity is measured in bytes.

• Different storage devices have different storage capacities.

• You need to choose a storage device which is suitable to your data storage needs.

Kilobyte (kB) 1024 bytes

Megabyte (MB) 1024 kilobytes

Gigabyte (GB) 1024 megabytes

Terabyte (TB) 1024 gigabytes

1. Write-protect tab (open=protected) 2. Hub3. Shutter4. Plastic Housing5. Paper Ring6. Magnetic Disk7. Disk Sector

These used to be the most common form of transferring data from one computer to another.

They had a storage capacity of 1.44MB.

They contained a floppy magnetic disk which used to wear out fairly quickly as the read/write needle used to have to be in contact with the actual disk.

Modern storage devices (such as USB pen drives) are larger in capacity and lack moving parts which means they last longer.

• Hard disks are the main storage device for most computer systems.

• Early hard drives used to be very large but hold a very small amount of data.

• Modern hard disks can store terabytes of data.

• They work similarly to floppy disks but contain more disks which can be written to from both sides.

• Optical Disks (similar to CDs) are read only memory.

• They hold about 700MB of data.

• They are written to and read from using a laser which passes over sectors on a CD.

• Some CDs are write once whilst others are re-writable.

• A CD has one layer to write to.

• A DVD has many layers to write to.

• The average storage size is 4.7GB.

• They are great for storing large files, which is why they are used for films and as backup mediums.

• Tapes are excellent at storing large quantities of data.

• They aren’t very good for reading from because data is stored serially.– This means that to find a file you have to

start at the beginning of the tape and play it until you get to the data you require.

– Unlike CD’s which have table of contents and can be read from very quickly because a laser can move to the correct position and read from sectors.

• They are often used for backing up large amounts of data such as on a server.

• These have replaced the floppy disk and now are very common.

• They have a large storage capacity for their size and work very quickly.

• They are more robust than a floppy disk due to the hard shell and lack of moving parts.

Media Description Use Capacity Transfer Speed

Cost per Megabyte

Floppy Disk

Hard Disk

CD

DVD

Tape

USB Stick

Complete the following table.

Once you have done that....

Describe five characteristics that you should be looking for in order to make a comparison between devices when choosing a storage device.

• Describe the different types of CD and explain their uses.

• Describe three different criteria to be used to compare memory sticks.

• What is a tape suitable to use for backing up data?

• How is a removable hard disk different from a portable hard disk?