Topic 5- selection And Use Of storage Flashcards
Primary storage
Programs and data are stored on chips inside the computer and are available Immediately by the central processing unit
2 types of primary storage
RAM (random access memory)
ROM (read only memory)
Secondary (or backup storage)
outside the computer.
Short delay while the data is obtained from the secondary storage
5 things secondary or backup storage can include
- Magnetic disk
- Magnetic type
- CD-ROM
- CD-RW
- DVD
RAM(random access memory)
fast temporary memory which loses its contents when the power is turned off
ROM (read only memory)
memory stored on a chip which does not lose data when the power is turned off
Volatile memory
memory which loses data when the power is turned off
Non-volatile memory
Memory stored on a chip which does not lose data when the power is turned off
RAM is…
- held on a computer chip
- volatile memory
- read/write so can be altered by the user
ROM is…
- held on a computer chip
- non-volatile memory
- used to hold instructions on computer
- contents cannot be altered by the user
Why is it important to have a large amount of memory?
- applications can run faster on their own
- more applications able to run at the same time
- able to quickly move between applications
What can be used to measure storage capacity and performance
- storage capacity (how much data can be stored usually measured in mb or gb)
- Storage density (ideally you want as much storage as possible in the least possible space)
- access time (time the storage device takes to access a particular piece of data)
- Transfer rate (once the data has been located it will need to be read and transferred to the computer. This measures the throughput of the data)
- physical size (storage devices need to be as small and light as possible)
- portability (some storage devices used for backup should be removable)
What is the amount of data stored and the instructions the computer can store measured by?
-bytes
1 byte= 8 bits
-A single character (letter,number or symbol on the keyboard) can be stored in one byte
-means that one byte is an extremely small unit of storage
3 ways of measuring storage/memory
- megabytes(mb)
- kilobytes(Kb)
- gigabytes(gb)
Smallest to largest file sizes
- Bits
- bytes
- kilobytes (Kb)
- Megabytes(Mb)
- gigabytes (GB)
- terabytes (Tb)
File size conversions of bits,bytes,kilobytes,gigabytes,megabytes,gigabytes,terabytes
Bits (0-1) Bytes=8 bits Kilobytes = 1024 bytes Megabytes = 1024 kilobytes Gigabytes= 1024 megabytes Terabytes= 1024 Gigabytes
Compression
Storing data in a file format that requires less space.
File compression
Files are often compressed before saving on the storage medium and this enables more files to be stored in the same space
Storage device capacity for CD
700Mb
Storage device capacity for Flash drive
4Gb
Storage device capacity for magnetic hard drive
320Gb
Floppy disks and drives
- flexible plastic disks
- not popular anymore because takes long to transfer the data from them (low data transfer speed)
- low storage capacity (1.44mb)
hard drives
Magnetic hard drives advantages
-Consist of a series of disks with a magnetic coating and a series of read/write heads which put the data onto or record it off each surface
Advantages:
- a very high transfer rate
- a very high storage capacity
Optical drives/disks
- flat circular disks on which data is stored as a series of bumps
- the way the bumps reflect laser beam lights used to reader the data off the disk
CD rom (compact disk- read only memory)
- what it is used for
- read only/random access?
- what is the data stored as
- storage capacity
- used for the distribution of software
- data is read only
- data is stored as an optical pattern
- large storage capacity (600mb)
CD-R definition
- Allows data to be stored on a CD but only once
- it is ideal for the backing up of data for storing Digital music
CD-RW (CD-rewritable)
Allows data to be stored on the desk over and over again-just like a hard disk
You can treat a CD-RW like a hard drive but the transfer rate is less and the time taken to locate a file is greater
- The media is not as robust as a hard drive
DVD (Digital versatile disc)
- DVDs have a much higher storage capacity than CDs
- are ideal for the storage of multimedia files such as MP3, digital images and video clips
DVD-ROM (Digital versatile disk-read only memory)
- Is used for the distribution of movies where you can only read the data off the disk
- A DVD-ROM drive can also be used for the reading of data off a CD
DVD+RW (Digital versatile disk +read/write)
What are they?
What they are also called?
storage capacity?
A DVD plus RW drive can be used to write to as well as read data from a CD
Also called DVD burners as they are able to be written on¬ just read from
-storage capacity=8.5 GB
Flash/pen drive
- Very popular stories media which offer cheap and large storage capacities and are an ideal media for photographs, music and other data files
- consist of printed circuit boards in a plastic case
Advantages and disadvantages of flash drive
A:-Small and lightweight& can be used with any computer-large storage capacity 4-30 GB -not affected by scratches like optical media
D: -small size means they are easily stolen or lost -turn left in computer by mistake&lost -do not have as high a transfer rate as magnetic hard disk drive
Magnetic tape What it is? Storage capacity? Used for? What is not used for?
- Magnetic tape stores the data on a plastic magnetic coated tape which is stored on a reel
- very large storage capacity (800 Gb) Sony introduced: 185 TB
- use for the backup of data&programs in large Systems(backs up data from a e-commerce business)
- not used for storage needed quickly as it has a large access time e.g used for data backup (lots of data, but rarely only accessed in an emergency)
Memory cards drives and memory cards
- memory cards are the thin cards found in digital cameras
- ideal storage media for photographs but can also be used for storing other types of data
- many computers and printers have drives that will read the data on different sized memory cards
- there are also portable memory card drives which attache to the USB socket of the computer
Data stored at different physical location from where it is used:
- websites
- emails
- those people who don’t have their own Internet servers will need to store their webpages and website on the server of an Internet service provider
- for a home user of the Internet their emails are stored on the storage devices of your Isp
Backup storage
What it is used for
Main requirements
Backup media/devices
- Used to hold copies of the original files in case they are lost
- main requirement for backup storage is that it should be portable& have a high storage capacity
- Pen/flash drives
- CD-RW and DVD-RW can be used as backup but are slow compared to other methods
