Memory Flashcards
What is computer memory often called? (2 things)
Main memory or primary storage
What forms does computer memory come in? (4 forms)
Random Access Memory (RAM)
Read only Memory (ROM)
Virtual memory
Flash memory
How can main memory be directly accessed?
By the CPU
What is RAM?
Random Access Memory
What is ROM?
Read Only Memory
Where are software programmes stored long term?
On the hard disk
The CPU can’t access a programme directly from the hard disk. How is it loaded and where?
It needs to be loaded by the operating system into RAM
Why do we call Ram Random Access Memory?
Because the CPU can access any memory location, at any time, in any order.
This makes programmes held in RAM able to run very quickly
The CPU can access any memory location, at any time, in any order. What does that mean for programs held in RAM?
It means that programmes held in RAM can run very quickly
What is RAM measured in?
Gigabytes (GB)
What would a typical PC have as RAM and what might it go up to for people using heavy applications?
4GB of RAM for a typical PC and up to 64GB of RAM for heavy application users
Why do we call RAM volatile and ROM non-volatile
Because RAM needs constant electrical power, if power is lost, everything stored in RAM will be lost, whereas ROM is non-volatile so it doesn’t require power to store the information inside it
What type of memory loses its data once power to the memory chip is broken?
Volatile memory
When RAM fills to capacity, how does the operating system create virtual memory?
The OS can mark sections of the hard disk to use as virtual memory
Why is virtual memory classified as ‘main memory’?
Because it can be accessed by the CPU
What does the operating system do with data and programmes that are in RAM but are not currently being used?
Moves the data and programmes into virtual memory
What does the operating system do with data and programmes that are in RAM but are currently being used?
Nothing, they remain in RAM
What is disk thrashing?
The constant switching between RAM and virtual memory can lead to a high rate of hard disk access - you can hear the hard disk working when it is being thrashed
What happens to the computers performance when the virtual memory is being heavily used?
It slows down
what two things are characteristics of ROM
Its contents cannot be overwritten / changed
It is non volatile - it keeps data even if there is a power cut
Until recently, ROM was used to store computer boot up instructions (BIOS). Where is BIOS stored nowadays?
In the flash memory
What is ROM still used for?
ROM is still used to store the MAC address on a network card
When you switch on your computer, what does BIOS do?
The BIOS checks the hardware is installed correctly (e.g. memory, graphics card)
What three things does the BIOS do when the computer is switched on?
1) Check the hardward is properly installed
2) Check the input/output devices
3) It loads the operating system
Flash is a non-volatile memory, however, unlike ROM, Flash memory can be used to both read and write data.
What else is often stored on flash?
It is often used to store the BIOS (so that changes to the instructions can be made when needed)
