1.2: MEMORY AND STORAGE Flashcards
What is RAM?
Random access memory; which is main memory
What is ROM?
Read only memory
What is the purpose of Ram?
Stores data and instructions for programs that are currently in use and the operating system
How is primary memory obtained? and why is it used?
- Data and instructions are copied into main memory when they are required
- because it would be too slow to access everything directly from the hard disk.
What is the purpose of ROM?
It stores data and instructions that are required for the BIOS and embedded systems
Define volatile and non-volatile
Volatile- loses all its data and contents when the device is switched off
Non-volatile- keeps all its data and contents even when the device is turned off
Can the instructions of RAM and ROM be overwritten?
RAM- yes, the contents of RAM can be changed at any time, simply by overwriting them with other data and/or instructions.
ROM- no, it is read-only memory, the instructions cannot be overwritten once it has been set by the manufacturer
3 differences between ROM and RAM
ROM:
- non volatile
- read only
- stores data and instructions for the BIOS/embedded systems
RAM:
- volatile
- can be read and written to
- stores data and instructions for programs that are currently open
EQ: An increase in RAM capacity can improve the speed of your computer. Explain why an increase in ROM size would not have the same effect.
-Rom is only required to be as large as the BIOS/ start up instructions inside it,
-therefore any additional space will make no difference.
New files cannot be written into the new space as it is read only
Why is primary memory effective? (3)
- built inside the computer.
- can be read from and written to extremely quickly.
- gives processor fast access to data and instructions
In what way is primary memory NOT effective?
Primary memory is comparatively limited in size, especially when compared with secondary storage.
What is virtual memory?
A section of a computer storage drive/ hard disk which is temporarily used as RAM.
What does virtual memory enable to happen and why is it effective?
- enables data in RAM and not currently being used to be transferred to the hard disk.
- frees up room in RAM for other programs and data
What happens when data from the hard drive is needed again?
any other unused data is transferred to the hard disk before the original data is SWAPPED back to RAM.
why is swapping not very time efficient? + additional reason
- secondary storage devices have slower access times than RAM, therefore the computer’s processing performance can be severely impaired and it will be noticeably slower
- disk thrashing
How could you improve processing performance
increasing the size of the RAM, thereby reducing the need for virtual memory.
What is cache memory?
-high-speed random access memory (RAM) built into processor.
What does cache store?
stores frequently used data and instructions
what is the correlation between cache and a computer’s processing speed?
The more cache memory a computer has, the faster it runs.
why does cache tend to be expensive? and what assumption can you make from this?
- due to high-speed performance, cache memory is more expensive to build than RAM.
- Therefore, cache memory tends to be very small in size.
What is Flash memory?
Flash memory is non-volatile memory than can be read from and written to
Characteristics of Flash memory: what is it ideal for?
requires little power and contains no moving parts,
making it an ideal storage medium for many modern devices
What can Flash memory also be used as?
external secondary storage, e.g) USB memory sticks and solid-state drives.
Explain why secondary storage is needed:
- long term (permanent), non-volatile storage/storing when the device is turned off
- to store data and files
Why is secondary storage crucial to a device?
Without secondary storage all programs and data would be lost the moment the device is switched off.
Do all devices need secondary storage? Give an example. (3 points)
- No
- embedded systems do not need to store data when the power is turned off.
- the instructions needed to run them are stored in ROM and any user data is held in RAM
Additional negative of magnetic SS? and how could this affect the SS?
- They are vulnerable to magnetic fields.
- a strong magnet might possibly erase the data the device holds.
What do SSDs use and for what reason?
-use non-volatile random access memory (RAM) to store data indefinitely.
What are some major advantages of SSD? (2)
- tends to have much faster access times than other types of devices and,
- because they have no moving parts, are more durable.
the 8 units of data storage:
o Bit o Nibble (4 bits) o Byte (8 bits) o Kilobyte o Megabyte o Gigabyte o Terabyte o Petabyte
