✅ 2. Memory and Storage Flashcards
What are the two types of storage?
Primary and Secondary Storage
Why do computers need primary storage?
- Computers need primary storage to temporarily store data, instructions and programs that the computer needs whilst it is in operation.
- Additionally, it is needed because it would be too slow to access eveything directly from the hard disk
What are the two types of primary storage?
- RAM
- ROM
What does RAM stand for?
Random Access Memory
What is the purpose of RAM in a computer system?
RAM stores data, instructions and programs that are currently being used by the processor
Describe 3 things about RAM?
- RAM is a volatile memory
- It can be written to and read from
- Directly accessible by the processor
What is volatile memory?
Volatile memory is when all the data is lost when the power is turned off
What are the advantages of having a computer with more RAM?
The more RAM a computer has, the more data and programs it can hold simultaneously
What does ROM stand for?
Read Only Memory
What is the purpose of ROM in a computer system?
ROM stores the start-up instructions for a computer and instructions and data that never need to be changed
Describe 3 properties of ROM
- Non-volatile
- Stores the start-up instructions for a computer
- The data is read-only and cannot be changed
Give 5 examples of instructions that are stored in the ROM?
- Store BIOS
- Stores the boot-up instructions
- Stores data that should not be changed
- Stores data that must be retained when the computer turns off
- Store firmware/OS fundamentals
What is BIOS?
BIOS stands for Basic input/output system that contains programs to check the hardware and load the operating system
What is virtual memory?
Virtual Memory is a small section of the secondary storage that is used as temporary RAM
When is virtual memory used?
Virtual memory may be needed if the computer does not have enough RAM to run a process because the RAM is full
Describe what happens in virtual memory
- A small section of the secondary storage is used as temporary RAM - known as VM
- Data that is not being used is moved from the RAM to the Virtual Memory
- The RAM can now be filled with new data
- When the program or data in the virtual memory is needed, then it is moved back to RAM and swapped with programs or data that are not needed in the RAM
- This is also known as swapping
Where is virtual memory located?
Virtual memory is located on the hard disk
What are the disadvantages of virtual memory?
- The processor has to wait while data is swapped between hard disk and RAM
- Constantly swapping data and programs between the RAM and the hard disk can cause disk thrashing, which decreases performance
- Virtual Memory has slower access times than RAM directly because it has to go back to the RAM first
What is secondary storage?
Secondary storage is the long term, non-volatile storage of data
Why do computers need secondary storage?
- Computers need secondary storage for the long term storage of files and data because it is non-volatile, which means that the data will not disappear when the computer turns off
- Computers also need secondary storage to store data and files
What types of data does secondary storage store?
- Programs
- Files
- OS
- Images, videos, text files
What are the 3 common types of secondary storage?
- Optical
- Magnetic
- Solid state
Give 3 examples of optical storage devices
CDs, DVDs and Blu-ray discs
Give 3 examples of magnetic storage devices
Hard Disk Drives, Magnetic Tapes, Old-fashioned floppy disks
Give 2 examples of solid state storage devices
Solid State drives and USB memory sticks
How do magnetic storage devices work?
- Magnetic storage devices use magnetic fields to magnetise a tiny section of a metal spinning disk
- Each tiny section is represented by a demagnetised 0 or a magnetised 1
- The magnetic read/write head is used to read and write data whilst the platter spins
How do optical storage devices work?
A laser light creates marks in a pattern
A laser light detects where the marks are and translates this into a readable format
Each 1 and 0 of the binary data is represented as microscopic holes (pits) on the surface of the disc
How do solid state storage devices work?
Solid State storage devices are made of microchips (switches)
The state of the switches determine if a 1 or 0 is stored
What do the following characteristics mean?
- Capacity
- Speed
- Portability
- Durability
- Reliability
- Cost
- Capacity - How much data can it store?
- Speed - How fast the data can be accessed
- Portability - How easy is it to move it from one place to another
- Durability - How well does it last e.g. if it is dropped
- Reliability - How consistently does it perform
- Cost - The cost per KB, MB or GB
What are the advantages of using hard disk drives?
- Cheap to buy
- Reliable
- Extremely large capacity
What are the disadvantages of using hard disk drives?
- Not very portable
- Not very durable as it can be affected by magnetic fields and heat
What are the advantages of using a solid state drive?
- Very fast read & write transfer speeds as there are no moving parts
- Very reliable
- Very Durable as Solid state has no moving parts so unlikely to break if dropped
- Very portable as they are very lightweight and small in size
- Silent
What are the disadvantages of using a solid state drive?
- Expensive per byte
- Smaller Capacity than HDD
What are the advantages of using an optical storage device?
- Very portable
- Cheap
- Reiable if looked after
What are the disadvantages of using an optical storage device?
- Low capacity
- Slow as it contains moving parts
- Easily damaged
Predict the characteristics of the optical storage type
Predict the characteristics of the magnetic storage type
Predict the characteristics of the solid state storage type
Describe the main disadvantage of primary memory compared with secondary storage
Primary memory is comparatively limited in size, compared to secondary storage
