1.2 Memory and Storage Flashcards by A A

What does primary storage consist of/

Random Access Memory (RAM)
Read Only Memory (ROM)
Registers & Cache

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State three items that are stored in RAM

Programs currently in use
Data currently in use
OS currently in use

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Purpose of primary storage

To hold the data and instructions which the CPU needs access to while a computer is running

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Properties of Primary Storage

With exception of ROM all volatile

Relatively small storage capacity compare to secondary storage devices. E.g. RAM is typically measured in GB, while SSD are normally measured in TB.

Very fast access times compared to secondary storage

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Properties of Secondary storage

All non-volatile
Much larger capacity compared to primary storage
Very slow access times compared to primary storage

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Define access speeds

how quickly can we read from and write to a device

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Given that RAM is volatile and has a relatively small capacity, whereas secondary storage is non-volatile and has a much larger capacity, then “What is the point in primary storage at all?”

WHAT IS THE NEED FOR PRIMARY STORAGE

Access times for primary storage is much faster than secondary storage

This speed of access is the main need for primary storage

The CPU can much more quickly access data from primary storage than secondary storage

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Different types of storage

Primary storage
Secondary storage

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Describe the purpose of ROM

Store BIOS (Basic Input Output System) -the boot up instructions

Stores data that should not be changed

Stores data that must be retained when the computer turns off

Stores firmware/OS fundamentals

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What is rom

Small piece of read only memory located on the motherboard

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what is rom

Software stored on the ROM

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Characteristics of ROM

Non-volatile

Programs may be stored in ROM in embedded systems

Small in comparison to RAM

Read only

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What is RAM

RAM is temporary storage of instructions and data

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Key characteristics of RAM

Holds the operating system, programs and data in use by the CPU when the computer is running

Volatile

It is readable and writeable

Much faster than the hard disk

Large in comparison to ROM

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Why is it important for ROM to be non-volatile

Store BIOS (Basic Input Output System) -the boot up instructions

Stores data that must be retained when the computer turns off

If rom was volatile (and contents were lost when the power was turned off), then the computer will not know how to start up.

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Define volatile

Volatile - When contents are lost when the power is turned off

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Define non-volatile

Non volatile (contents remains when power

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Explain how virtual memory can compensate for the lack of RAM in a computer

VM is used when RAM is full

Part of the secondary storage used as (temporary) RAM

Data from RAM is moved to the
secondary storage/VM (to make space in RAM)

RAM can then be filled with new data

When data in VM is needed it is moved back to RAM

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Explain why it is beneficial to get more RAM instead of relying on virtual memory

More RAM will improve the
performance of the computer
(//More RAM will speed up the access to data)

Excessive use can cause disk
thrashing which decreases performance

VM is slower to access than RAM directly (because it has to go back to RAM first)

Moving data between RAM and VM takes processor time

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Why might virtual memory be needed in a system

Virtual memory is needed when there is not enough physical RAM to store the open programs

What happens to programs to programs when they are not currently being executed and what happens to programs when they are needed - regarding virtual memory

Programs are transferred out to virtual memory from the RAM, when they are not currently being executed.

Programs are transferred back to the RAM from virtual memory when they are needed

Where is virtual memory held

It is held on the hard disk (a location on secondary storage)

Why computers have secondary storage

Secondary storage is needed because ROM is read-only and RAM is volatile

What is secondary storage needed for

Storage of programs and data when the power is turned off

Semi-permanent storage of data that can change

Backup of data files

Archive of data files

a. What does solid state media mean?

Storage media with no moving parts Device that uses flash memory

State some types of programs that are held on secondary storage media

The operating system Programs and data are held here when not in use

Three common types of secondary storage

Optical Magnetic Solid state

Define a 'drive'

The device that reads and writes data from secondary storage

Define 'media'

What the data is actually stored on (is referred to as the media)

Types of optical media/storage devices

CD - Compact disc Compact disc read-only (or CD-R) Compact disk read-write (or CD-RW) Digital Versatile disc read-only (or DVD-R) Digital Versatile disc read-write (or DVD-RW) Blu-ray

On average how much data can CDs, DVDs and Blu-Ray discs hold

CD - 700 MB DVD - 4.7 GB Blu-Ray 25GB

a. Which type of secondary storage is most suitable for distributing a movie?

Optical

b. What is the most suitable storage device for distributing a movie?

DVD/Blu Ray

c. What is the most suitable secondary storage device for distributing music tracks?

Positives of optical storage media

Portable Cheap (byte for byte) compared to other types of storage Light weight, thin

Negatives of Optical storage media:

Slow access times (slow read/write speeds) Prone to scratches. (These scratches could result in the optical media not functioning properly) Low capacity compared to other types of storage

d. What are reasons you chose the device (cd) you did for distributing music tracks?

* Cheap to produce. * Easily portable. * Enough capacity for the music tracks. * Can be read by other devices. * Read only/can’t be over written.

Types of magnetic storage media

Hard disk drive Magnetic tape

State the disadvantages for using magnetic tape to store data

* Slow to write to and read from memory. * All data has to be read before reading the data you want. * Data could be corrupted if close enough to a magnetic field. * Additional equipment needed to read data from tape. Fragile (disadvantage in general)

Positive of magnetic storage media

Cheap (BYTE FOR BYTE) Large capacity

Adv. of magnetic

Hight storage capacity Quick to access data Cheaper (byte for byte) than SSD Hard disks perform better if they are defragmented

Disadv. of magnetic

Has moving parts, which eventually fail

Solid state advantages

No moving parts, very reliable Very quick to access data Medium storage capacity No noise Low power No need to defragment Portable/robust

Solid state disadv.

Limited number of read/write cycles Expensive (byte for byte) compared to other types of storage * Can get lost easily. (memory stick) * The metal part that is inserted into the USB port can become bent or damaged

Types of solid state storage media

SSD, Memory sticks, Flash memory cards

Fastest to slowest in terms of average read/write speed

Slowest Optical disc Memory card Magnetic tape HDD SSD Fastest

Cheapest to Priciest in terms of average cost (per GB - BYTE FOR BYTE)

Cheapest Magnetic tape Optical disc HDD Memory card SSD

Lowest to highest in terms of average capacity

Lowest Optical disc Memory card SSD HDD Magnetic tape