RAM is memory used
for storing programs
and data in use
Features of RAM
• volatile and so lost when the
computer power is switched off
• allows computer to
read data quickly
•allows computer to
run applications
ROM - Read Only Memory
Used for Firmware programs
needed to boot up a device,
referred to as Boot Strap
and Start-up.
Firmware is permanent software
programmed into ROM.
Features of ROM
• is non-volatile and keeps its content
when the computer power is switched off
• allows computer to check hardware devices are
working during start up it will report any errors
• it stores the BIOS, Basic Input Output system
and allows you to setup your computer
• locates the operating system and passes control to it
Virtual Memory
additional memory to a computer’s
RAM, held on the storage device
either a Hard disk or Flash memory.
Volatile and it is used when the RAM
is low on small and the computer
wants to run additional processes.
Disadvantages
It is slower than
RAM as data has to
transfer between
the CPU and the
storage device
If used extensively can lead to Disk
Thrashing and possibly a Head crash,
which could damage the hard disk and
loose data
Disk Thrashing - is when a computer's virtual
memory subsystem is in a constant state of
paging. This sometimes occurs if a CPU is
attempting many processes at once
Flash Memory
a type of non-volatile memory (that is it
retains its data when the power is turned
off). Data is stored in units called blocks.
Advantages
• It takes less space
Transfer of data
Being Solid State, they
are more mobile
Disadvantages
• Cost more than traditional drives,
• Less space than equivalent hard disks
a Flash drive on a
laptop might be 160 or
250 Mega Bytes but a
Hard disk on a laptop
might be 1 or 2 Terra
bytes.
E.g. -Smart phones, tablets
and some laptops.
Storage
Input Output and Storage Devices
An Input Device is used to enter
of data. E.g. a Computer Mouse
or Keyboard
An Output Device is used to
present information, the result of
processing to the user. E.g. a
Printer or a screen
A Storage Device is some hardware to
hold data in a binary format for
processing later.
Computer Storage is somewhere to store
electronic data. Data stored in random
access memory or RAM and cache memory
are referred to as Primary storage.
Hard disks and other devices
such as solid-state devices
and optical drives are called
Secondary storage.
Secondary storage is used to
store programs, data and
other files that would
otherwise be lost when the
power is turned off
Types of
Secondary
Storage
Magnetic hard disks- cheap, large capacity, slower
than flash, commonly used within personal and
commercial computers to store operating systems,
and other files and programs.
Optical disks (CD, DVD and Blue Ray) - distribute
programs, videos and large data files as read only
files. CD-RW and DVD-RW (RW is Read, Write) are
used to store backup copies of files and to transfer
files. Slow, inexpensive and have capacities of
700MB (CD), 4.7 GB (DVD) and 9GB (Blue Ray).
Flash (Solid State) memory is very flexible and can store
many GB of data in a small space. It has good access times,
more expensive than Magnetic or Optical storage. It is used
to store data in smart phones, cameras and tablets. The
pen drive or USB stick is a very example of a Flash drive and
is used extensively to transfer files and backup.