- A program consisting of a larger number of simple instructions drawn from a reduced instruction set (RISC) may run faster than an equivalent program consisting of a smaller number of complex instructions drawn from an extended instruction set (CISC).
Number of Processors
- A single processor can only run 1 instruction at a time. To get beyond this you need an additional processor. This allows more than one instruction to be run and increases the speed of the computer. Programs and computers have to be written to make use of the second processor.
Bus Speed
- The speed of the computer is also determined by how fast the data can travel. Data travels down buses
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Increasing the speed of the bus decreases the waiting time and increases the speed. The speed of the bus is determined by the clock speed
RAM
- The more RAM you have, the more instructions you can store without having to access the disk which is slow. It decreases disk thrashing
- Cache memory is even faster and with more of it, the machine runs faster still
Dedicated Processing Devices
- Instead of using the processor to do all the processing you can use specialist processors to take some of the load and thus speed up the machine. These include sound and graphics processors
Making a Machine Run Faster
Replace motherboard
Processor
- Add second/subsequent processor
- Overclocking processor
Dedicated device
- Dedicated processing device – sound card/graphics card, etc
RAM
- Increase RAM – holds larger swap files/more data
Transputer
- A microprocessor on a single chip
- It includes a small amount of memory on the chip itself
- Can be connected in parallel increasing overall speed of processing
- Used in embedded applications where the program to be run does not have to be retrieved from disk – therefore it is faster.
Input Devices
- Eye-Type
- Puff Suck Switch
- Foot Mouse
- ADC
- Sensor
- Push Switch
- Digitiser
- Graphics Tablet
- Digital Camera
- OCR
- Scanners
- Touch Screen
- Microphone
- Trackerball
- Mouse
- Joystick
- Numeric Keypad
- Keyboard
Input Entry Devices
Discrete Entry
- provides a single data entry for the system, for example:
- A mouse button, touchscreen or keyboard – each data entry is single only
Continuous Entry
- This is where the data being entered is constant
- Sensors giving constant data entry to the system – weather stations, thermostats in a house, a nuclear power station, the movement of the mouse.
Physically Activated
- Activated by a part of the anatomy
- E.g. mouse, joystick, foot, head, eye, etc.
Output Devices
- Buzzer
- LED
- Plotter
- Monitor
- Printer
- Loud Speaker
Examples
Loud Speaker
- Used to give confirmation of actions
- Can be used to read lines of text
- Increased use with CDs and Music (MP3s)
- Music technology requires specialist sound output devices.
LED and Buzzer
LED
- Can display the status of a device
- FDD light displayed when in use
- A light on a Printer indicates status - on-line or off line for example.
- Can be used to signal to hearing impaired people
Buzzers
- Gives confirmatory actions
- Set sounds to events in Windows
- Bar Codes beep to indicate successful entry
Printers
Three main types of printers:
- Impact Printers
- Inkjet Printers
- Laser Printers
Choice of:
Selection of different resolutions
Impact Printers
- Physical Connection between print head and paper
- Noisy
- Slow (chain printers can be very fast)
- Cheap to run
- Colour or Black and White
- Low Resolution
- Can do Carbon Copies
- Print on multi part paper
InkJet Printers
- Ink is fired at the page and the number of DPI can be very high
- Colour or black and white
- High running costs
- Faster than a dot matrix but not as fast as laser
- Can not print carbon copies
Laser Printers
- High Quality Images
- Fast Printing
- Colour or Black and White (Colour is expensive)
- Medium to low running costs
- Excellent Quality
- Need special transparencies to produce OHPs
- Cannot do Carbon Copies
Monitor (VDU)
- Most common Output device
- Range of Sizes – standard is 17”, but 21” or greater is available for specialists:
- For example, designers
- Newspapers and magazines
- High quality output
- Bulky, but LCD screens can reduce footprint size
- More expensive than standard monitors
- Less affected by glare
- Fewer health issues compared to standard monitors
- Possible health issues with standard VDU’s
Storage Devices
- CD ROMs
- Floppy Disk
- Hard Disk
- Tape
Role of Storage Devices
- To store data that is not currently being processed
- Non volatile storage of programs and data
- Sometimes referred to as secondary store or mass storage.
Tape
- Serial Access to data
- Used almost exclusively to hold backup data
- Can hold in excess of 100Gb of data
- Specialist devices required to read the tape
- Slow access to data.
Hard Disk
- Sealed unit holding many GB of data
- Fast direct access to the data.
- Two types (standards):
- SCSI (Small Computer Systems Interface)
- High speed of transfer (historically – catching up)
- Specialist card required – controller separate from device
- Can daisy chain devices
- MTBF (mean time between failures) greater on SCSI – reliability
- IDE (Integrated Device Electronics)
- Standard interface in PC’s (More common than SCSI)
- Cheaper and slower than SCSI (catching up in speed)
Floppy Disk
- Floppy Disk Drive is standard on PCs
- Portable between machines
- Limited storage capacity (1.44 MB)
- Slow access to data
- Can be set to read only by use of a tag
- Inexpensive
- Constant use increases unreliability
CD ROM
WORM (Write Once Read Many)
- Holds 650 MB Data
- Used for static data (data which does not change)
- Encyclopaedias
- Software Programs
RW CDs allow you to rewrite onto the CD.
- This is only possible a limited number of times and requires specialist equipment. (approximately 1000)
DVD now available – Holds 12GB of data
CDs/DVDs used to hold Music, Video, Pictures, etc
Other Devices
- Zip disks (100 MB, 250 MB, 750MB)
- Super Floppy Disk (120 MB)
- Jazz Disks (1GB +)
- Flash Memory (256+MB and increasing)
- All storage devices are pushing amount of storage they can hold
- Figures constantly changing
Magnetic v Optical Devices
Magnetic
- Can be reused many times
- Very large storage capacity
Optical
- RW CD ROMs/RW DVDs exist – limited life cycle
- Limited storage capacity
Backup and Archive
- Making copies of data or programs in case the originals are lost or corrupted.
- The storage of information for long periods of time.
- Removing the data from the original medium and transferring it to off line/secondary storage
Speed of Backup (Direct or Serial) and speed of recovery
Amount of data (MB or GB)
Portability (Tapes, Removable disk)
Compatibility with other systems (CD, tape, etc)
Hardware Related to Use
Answers based on:
- Portability
- Specialist hardware required
- Cost
- Speed
- Ease of use
- Compatibility
Types of Software
- Operating Systems
- User Interfaces
- Utilities
- Translation
- Application
- Programming Languages
Operating Systems
- A program or suite of programs that control the entire operation of the computer.
- Deals with the basic functions of the computer.
- At a technical level, it handles the basic and central functions such as input and output operations and interrupts. Examples include: MS-DOS, OS/2, UNIX, RISC-OS, Windows XP, LINUX, BeOS, etc.
User Interfaces
Methods by which the user can interface with the operating system/application
- Command line
- Dialog boxes
- Menus
- Windows
Utilities
- Designed to perform a commonplace task, for example the transfer of data from one storage device to another, sorting a set of data, disk editor.
- They are designed to make the operation of the computer easier.
- Other examples: formatting programs, backup programs, anti-virus, etc.
Translation
- Programs which convert a program from one language to another, for example from low level language to machine code.
- This is the general name for three types of translators:
- Assemblers
- Compilers
- Interpreters
Application Software
- Generic
- Tailor-Made
- Off-the-shelf
- Programming Languages
- Cross over between categories:
- Generic is off-the-shelf
- Programming languages can be off-the-shelf and used to create tailor-made software
Generic
- These are off-the-shelf packages which do not meet a specific purpose but serve a general purpose
- For example:
- Microsoft Office and components
- Corel Suite
- Lotus Suite
- Word Processors, Spreadsheets, Databases
- The software can then be customised to produce the result you want.
Tailor-Made
Either:
- The application is written for the purpose by a software house
Disads: Time consuming, expensive, limited support/books.
Ads: Fulfils purpose, individual support
Or:
- A generic application is customised using a programming language
Disads: Need to purchase the application and you get more than required.
Ads: Cheaper, lots of support.
Off-the-Shelf
- Purchasing solutions from a shop without alteration
- For example:
- SAGE payroll package
- Heritage Library Database
- The idea is to be able to open the package and run the software which delivers a specific solution
- Can be generic (word processors)
Programming Languages
- There are a variety of programming languages available.
- Each language has a specific purpose
- FORTRAN – Formula Translation
- Mathematical and Scientific
- COBOL – Common Business Orientated Language
- Business, Data Processing
- Languages can also be used to enhance the application:
- Use of VBA to write macros, etc