1.3: Primary Storage (Memory)
Eduqas / WJEC
Storage in a computer system is split into two categories.
Very quick to access because it is attached to the motherboard.
Typically smaller in storage size.
Sometimes called ‘main memory’.
Slower to access because it is not directly embedded on the motherboard.
Typically larger in storage size.
Sometimes called ‘backing storage’.
Storage is also split into two types - volatile and non-volatile.
Volatile storage is temporary - data is lost whenever the power is turned off.
Non-volatile storage saves the data even when not being powered. Data can be stored long-term and accessed when the computer is switched on.
Types of Primary Storage (Memory)
Random Access Memory (RAM)
RAM is volatile (temporary) storage that stores all programs that are currently running. RAM also stores parts of the operating system to be accessed by the CPU.
RAM is made up of a large number of storage locations, each can be identified by a unique address.
ROM is non-volatile storage that cannot be changed.
ROM stores the boot program / BIOS for when the computer is switched on. The BIOS then loads up the operating system to take over managing the computer.
Cache memory is volatile (temporary) storage that stores data that is frequently accessed.
It is very quick to access because it is closer to the CPU than other types of memory like RAM.
The three levels of cache memory are explained in more detail in 1.5.
(Random Access Memory)
(Read Only Memory)
Flash memory is editable so it can be read and written to. It is also non-volatile so it can be used for long-term data storage even when the system is not powered on.
Flash memory is also used for secondary storage devices like USB sticks and solid-state drives - see 1.4.
When a computer system is running slowly and RAM is near full capacity, the operating system will convert storage space on the drive into temporary memory.
This virtual memory slows the system down because it takes longer to access the drive than it does to manage RAM.
Transferring data between RAM and virtual memory is called paging.
1.3 - Primary Storage (Memory):
1. Describe the differences between primary and secondary storage. This could be done in a table with the column headings 'access speed', 'storage size' and 'also known as'. 
2. Explain the difference between volatile and non-volatile storage. State an example of both types. 
3. For each type of memory below, describe it and state what information is stored within it:
a. Random Access Memory (RAM) 
b. Read-Only Memory (ROM) 
c. Cache memory 
d. Flash memory 
e. Virtual memory