ICT-INFO 1- Topic 5 Selection and use of storage requirements,media and devices

 Selection and use of storage requirements,media and devices

Primary- In chips inside computer- ROM- Read only memory - RAM -Random access memory available immeadiatley by the CPU 

Secondary- Backup 

• Magnetic disk
• Magnetic Tape
• CD-ROM (compact disk read only memory)
• CD-RW (compact disk re-writable)
• DVD

RAM

• Fast 
• Temporary 
• Programs
• Data
• Stored only when power is supplied
• On a computer chip
• Called Volatile Memory because the contents dissapear when no power is supplied
• Read/write so can be altered by user

ROM

• Fast
• Permenant
• Holds instructions to start computer
• Held on a computer chip
• Called non-volatile memory because doesn't dissapear when power is turned off
• Contents cannot be altered by user

If you have a large memory then:

•  Applications run faster on their own
• More applications can run at once
• Quickly move between applications

Storage Capacity- How much data can be held

Storage Density- How compact it is

Access Time- How long it takes to access data

Transfer Rate- How long it takes to transfer data onto the computer from the device

Physical Size- Need to be as small and light as possible

Portability- Some need to be removable 

Bit (0 or 1) the smallest unit

Byte

Kilobyte (Kb)- 1000 bytes

Megabyte (Mb)- 1000 kilobytes

Gigabyte (Gb)- 1000 megabytes

Terabyte (Tb)- 1000 gigabytes

• Before Saving
• Enables more files to be saved

CD- Typical storage capacity- 700Mb

Flash Drive- Typical storage capacity- 4Gb

Magnetic hard drive-Typical storage capacity- 320Gb

Floppy disks and drives:

• Flexible plastic disks
• Coated with a material which can store data as a magnetic pattern
• Removable
• Transferable
• Not popular 
• Low transfer speed
• Very low storage capacity 1.44Mb

Hard drives:

• Series of disks
• Magnetic coating
• Series of read/write heads
• High transfer rate
• High storage capacity

CD-ROM

• Software
• Read only
• Data is stored as an optical pattern
• Large storage capacity 600Mb

CD-R (compact disk recordable)

• Data can be stored only once

CD-RW 

• Store over and over again
• Low transfer rate

DVD (digital versatile disk)

• High storage
• Multimedia files (mp3,video,images)

DVD-ROM 

• Movies
• Read only
• Reading of data off a CD

DVD-RW

• Write
• Read data
• 4.7Gb for old
• 8.5Gb for newer

• Plastic magnetic coated tape
• Stored on a reel
• Huge storage capacity (around 800Gb) 
• Back up of data and programs in large systems
• Takes time for the data to be found
• Suitable for an e-commerce business 

• Very popular
• Cheap
• Large storage capacity (up to 30Gb)
• Ideal for photographs,music and other data files
• Printed circuit boards enclosed in a plastic case
• Small and lightweight
• No moving parts
• Reliable
• Work when scratched 
• Easily stolen
• Often left in computer by mistake and lost
• Not got a high transfer rate

• Thin cards
• Ideal for photographs but can be used for other types of data too
• Many computers and printers have drives to read them 

• Networked computers
• A Blog
• On-line backup websites 
• Websites
• Emails

Ideal storage device would be:

• Cheap
• Very large storage capacity
• Extremely fast access time
• Extremely high transfer rate
• Robust
• Not be affected by scratches,heat,magnetic fields etc
• Small size
• Attach to different devices eg digital cameras, computer etc

This doesn't exist so compromise will have to be made

• Hold copies of original files
• Don't need to be immediately accessible by the computer
• Pen/flash drives
• CD-RW And DVD-RW