2.1: Primary Storage (Memory)
Primary vs Secondary Storage
Storage in a computer system is split into two categories:
Very quick because it is directly accessed by the CPU.
Typically smaller in storage size.
Sometimes called ‘main memory’.
Includes RAM and ROM.
Volatile vs Non-Volatile 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.
Why do Computers need Primary Storage?
Primary storage is low-capacity, internal storage that can be directly accessed by the CPU.
Program instructions and data must be copied from the hard drive into RAM to be processed by the CPU because primary storage access speeds are much faster than secondary storage devices like the hard drive.
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.
(Random Access Memory)
(Read Only Memory)
Programs must be stored in RAM to be processed by the CPU. Even if there is insufficient space in RAM for all programs the computer can use the hard disk drive (HDD) as an extension of RAM - this is called virtual memory.
If new data is needed to be stored in RAM then unused data in RAM is moved to the hard drive so the new data can be transferred into RAM.
When required, the data can be moved back from virtual memory into RAM. Using virtual memory allows users to run more programs simultaneously with less system slow down.
2.1 - Primary Storage (Memory):
1. Describe the differences between primary and secondary storage. 
2. Explain the difference between volatile and non-volatile storage. State an example of both types. 
3. Explain why the computer requires primary storage. 
4. 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. Virtual memory 
Secondary Storage: (Section 2.2)
Slower because it is not directly accessed by the CPU.
Typically larger in storage size.
Used for the long-term storage of data and files because it is non-volatile.
Includes magnetic, optical and solid state storage.