Primary & Secondary Storage Flashcards
All 32 cards in this deck
What is primary storage?
Storage that holds the data, programs and instructions currently in use by the processor.
Why does a computer system need primary storage?
So the processor can access the data and instructions it is currently using very quickly.
What is cache memory?
High-speed volatile memory built into the processor that temporarily holds data and instructions the processor is likely to reuse.
Why does cache memory speed up processing?
The processor does not have to wait to fetch the data and instructions from the slower RAM.
True or false? Cache memory is slower than RAM but much larger.
False. Cache is faster than RAM, but it is very small and more expensive to build.
What is RAM?
Volatile primary storage that loses its contents when power is switched off and can be read from and written to.
What is ROM?
Non-volatile primary storage that keeps its contents when power is switched off and can only be read from, not written to.
What does RAM hold while a computer is running?
The operating system and the programs and documents currently open/in use.
State two items that would be stored in the ROM of an embedded system.
e.g. a car's 'Follow Me' distance-keeping system
- Start-up instructions / BIOS / bootstrap (where to find the OS).
- Firmware / the instructions to run the 'Follow Me' system.
State three items of data that would be stored in RAM in a car's 'Follow Me' distance-keeping system.
Current distance from the car in front; the set distance from the car in front; the current speed of the vehicle. ('speed' or 'distance' alone is not accepted.)
What is virtual memory?
The use of secondary storage, such as a hard disk, as extra primary memory when RAM is insufficient.
What is the name of the process of transferring data between RAM and the hard disk when using virtual memory?
Swapping.
What are the steps showing how virtual memory works when RAM becomes full?
e.g. opening another program when RAM is already full
- Data in RAM not currently being used is transferred to the hard disk.
- The freed RAM space is used by the new program.
- When the swapped-out data is needed again, other unused data is moved to disk and it is swapped back into RAM.
True or false? Using virtual memory makes a computer run faster.
False. It runs slower, because the processor must wait while data is swapped to and from the slower secondary storage.
How can a computer's need to use virtual memory be reduced?
By increasing the amount of RAM, so it is less likely to become full.
Give two reasons why an embedded system might not need virtual memory.
e.g. a car's 'Follow Me' distance-keeping system
It only stores a few specific items in RAM, so is unlikely to run out of RAM; only one/few programs run at a time (no memory-intensive tasks) and the RAM is designed to meet the system's requirements.
What is secondary storage?
Non-volatile storage used to hold data, files and programs permanently, including when the computer is switched off.
Why does a computer need secondary storage?
Because RAM is volatile and limited in size, so data and programs must be stored permanently somewhere with a large capacity.
Give two differences between primary and secondary storage.
Primary storage is much faster and directly accessible by the processor; secondary storage is slower, non-volatile and has a far larger capacity.
True or false? A program stored on a hard disk must be loaded into RAM before the processor can run it.
True. The processor works with data and instructions held in primary storage.
Name the three common types of secondary storage.
Optical, magnetic and solid state.
Give two examples of optical storage media.
CD, DVD or Blu-ray disc.
Give two examples of magnetic storage devices or media.
Hard disk drive (HDD) and magnetic tape.
Give two examples of solid state storage devices or media.
Solid state drive (SSD) and USB memory stick (also SD/memory cards).
What is flash memory?
Non-volatile memory that can be read from and written to, is fast (but slower than RAM), uses little power and has no moving parts.
True or false? Solid state storage contains moving parts.
False. It has no moving parts, making it robust, portable and faster to access than magnetic or optical storage.
Name the six characteristics used to compare storage devices and media.
Capacity, speed, portability, durability, reliability and cost.
Give one advantage and one disadvantage of a solid state drive compared with a magnetic hard disk drive.
Advantage: faster access with no moving parts, so more durable and lower power. Disadvantage: higher cost per gigabyte.
Why is flash (solid state) memory suitable for tablets, smartphones and digital cameras?
It is small and light, has no moving parts so is robust, uses little power and is fast to read from and write to.
Which type of storage is most suitable for backing up very large amounts of data as cheaply as possible?
Magnetic storage (hard disk drive or magnetic tape) — large capacity at a low cost per gigabyte.
Give two drawbacks of storing data in the cloud rather than locally.
You need internet access (speed depends on the connection), and you have no control over security, relying on the provider; there may also be an ongoing subscription cost.
Give two advantages of storing data remotely (in the cloud) rather than locally.
Data can be accessed from anywhere with an internet connection and shared easily; no need to buy and maintain your own storage hardware.