Computer Systems Nat 4/5 Computing Science Input, Output and Backing Storage

Lesson Aims  By the end of this lesson:  Pupils will be able to: Describe the features, functions and uses of: keyboard, mouse, microphone, touchpad, digital camera, scanner, webcam Describe the features, functions and uses of monitor, LCD panel, inkjet and laser printers, loudspeakers Compare devices using appropriate characteristics including resolution, capacity, speed of data transfer, cost

Input Devices Nat 4/5  An input device is a device which creates some new information to put INTO the system

Output Devices Nat 4/5  An output device is a device which gets information FROM the system

Input/output Devices Nat 4/5  You have to be able to compare these devices in terms of appropriate characteristics such as:  Resolution  Capacity  Speed of data transfer  Cost

Backing Storage

Storage Terms TermAbbreviationDescription Bitbinary digit, 0 or 1 BIGGER -> Bytea group of 8 bits – Single Letter KilobyteKb1024 bytes MegabyteMb1024 Kilobytes GigabyteGb1024 Megabytes TerabyteTb1024 Gigabytes Nat 4/5

Sequential Access  To go from file A to file Z in a sequential- access system, you must pass through all files in order.  Sequential access is sometimes called serial access Direct/Random Access  Refers to the ability to access data at random. In a random-access system, you can jump directly to file Z.  Disks are random access media, whereas tapes are sequential access media Types Of Access Nat 4/5

Backing Storage  Backing storage is used to save permanent copies of your files onto.  There are 3 main types  Magnetic  These use magnetic fields to store the data  Floppy Disks/Hard Disk Drives  Magnetic Tapes  Optical  These store data by means of lasers ‘burning’ a disk  CDROM/DVD/Blue Ray  Solid State  This uses no moving parts at all, uses memory chips  USB Drives  SSD Hard Drives Nat 4/5

Floppy Disks  Floppy Discs are small pieces of plastic film wrapped in a plastic case, they are fast becoming very scarce due to their slow transfer speed and limited capacity, have basically been replaced with USB Flash Drives Nat 4/5 Type Of AccessDirect/Random Capacity1.44 Megabytes PortabilityVery – Only requires another drive Transfer RateVery Slow – 500Kbps PriceApprox 25p per Disk

Hard Disk Drives (HDD’s)  Hard Disk Drives are usually stored inside the computer. They use disks of metal which are magnetically charged.  These are read by a small head – like a record player, which moves over the disks. Nat 4/5 Type Of AccessDirect/Random CapacityUp to 3TB PortabilityNot portable Transfer RateUp to 600Mbps PriceApprox £40 - £220

Magnetic Tape  Magnetic tapes are essentially the same as music tapes.  To access a file you have to sequentially go through every file by fast forwarding or rewinding.  They are however relatively cheap and easy to store.  Often used for backups Nat 4/5 Type Of AccessSequential CapacityUp to 80GB PortabilityVery portable, requires another drive Transfer RateUp to 7Mbps PriceUp to £20 per tape

Optical Storage – CD/DVD  CD and DVD’s are optical media – a laser is used to burn holes (pits) into the surface of the disk.  CD/DVD-R are recordable once  CD/DVD-RW are rewritable more than once Nat 4/5 Type Of AccessDirect/Random CapacityCD: 700MB (80 minutes audio) DVD 4.7GB up to 50GB Blue Ray PortabilityVery portable, requires another drive Transfer RateApprox 130Mbps PriceCDR: 20-30p DVDR: 30p-£1

USB Flash Drives  USB (Universal Serial Bus) flash drives use memory chips to store data, this means there are no moving parts at all – this is called solid state storage, this means they are very robust.  These are often used in MP3 – Players – Ipod Nano/Shuffle uses this.  Some are even waterproof or branded with company logos Nat 4/5 Type Of AccessDirect/Random CapacityUp to 128GB PortabilityVery portable, only requires USB port Transfer Rate10-30MBps Price£10-£100+

Summary  There are three main types of backing storage  Optical  Magnetic  Solid State  There are two main types of access  Sequential  Direct/Random  Input Devices put information INTO the computer  Output Devices get information FROM the computer