-PRIMARY STORAGE is used to store programs
and data currently used by the computer. When a
user needs to run a program, it is loaded from disk to
primary storage.
-Another term for primary storage is RAM or
Random Access Memory. It is given this name
because data can be stored anywhere within the
available memory.
-RAM is volatile (i.e. any data stored in RAM is lost
when the device is powered off)
-ROM or Read Only Memory is non-volatile (i.e.
any data stored in RAM is not lost when the device is
powered off) –it is stored permanently.
-ROM can be used to store the BIOS (i.e. the
program that boots up and loads the Operating
System when the computer turned on)
-VIRTUAL MEMORY is used when the computer
is short of RAM. This involves the hard disk
being used as memory instead of RAM.
-This is not ideal as the speed of a hard disk is
MUCH slower then RAM.
GCSE COMPUTING
KNOWLEDGE ORGANISER 1.2 MEMORY AND STORAGE
The need for primary storage
The difference between RAM and ROM
The purpose of RAM in a computer system
The purpose of ROM in a computer system
Virtual memory
The need for secondary storage
Common types of storage:
Optical
Magnetic
Solid state
1.2.1 PRIMARY STORAGE (MEMORY)
1.2.2 SECONDARY STORAGE)
1.2.3 UNITS
-Optical Storage includes CD, DVD and Blu-ray.
Data is written to optical storage media using a laser.
- The capacity of this type of media ranges from 640
megabytes (CD) to 50 gigabytes (Blu-ray)
- Since it involves the use of moving parts,
access/data transfer speeds are slower than for
other types of media.
-Magnetic Storage media include hard drives and
tape and can have a huge capacity (100’s of
terabytes)
- Magnetic storage media devices involve the use of
moving parts.
- This means that they have comparatively slow data
read and write speeds and can be prone to damage.
-Solid state media is also known as electrical or
flash storage.
- Solid state has the fastest transfer speed out of all
the three types of media, since it features no
moving parts
- This also makes it more robust than other forms of
storage and in addition they consume less power
- However this form of storage offers lower capacity
than other forms of media and is still comparatively
expensive.
Examples –CD, DVD, Blu-ray Examples –hard drive, magnetic tape, external hard drive
Examples –Solid State Drive, flash drive, SD Card
Criteria for
choosing
secondary
storage
REVISION NOTE
When recommending
a method of
secondary storage,
always consider the
context in which the
data will be used
The units of data storage:
Bit
Nibble (4 bits)
Byte (8 bits)
Kilobyte (1,000 bytes or 1KB)
Megabyte (1,000 KB)
Gigabyte (1,000 MB)
Terabyte (1,000 GB)
Petabyte (1,000 TB)
How data needs to be converted into a binary format
to be processed by a computer
Data capacity and calculation of data capacity
requirements
Computers are electrical devices;
their components are made up of
millions of circuits. Each circuit
contains switches which can be
Either ‘on’ or ‘off’. These can be
represented by the values 1 and
0. This is called binary. 10
ALL data is stored and processed in binary form –this
includes text, images, sound and video.
SPEED/COST
This shows speed vs capacity of
primary/secondary storage
CAPACITY
