RAM contains programs,
instructions and data that are
currently being worked on (in
use). RAM is volatile meaning that
when the power is removed then
all data is lost.
ROM (Read Only Memory) is
usually a flash memory chip on
the motherboard that contains
instructions needed to start up
(boot) the operating system. ROM
is non-volatile meaning that when
power is removed, data is retained
on the chip.
The ROM chip in a PC is usually called BIOS
Flash memory refers to memory that
is solid state (i.e. No moving parts)
that retains data even when power
is removed.
Virtual memory is for when
the computer runs out of
available RAM and so uses
part of the HDD (Hard Disk
Drive) instead. This is not
desirable however, as the
HDD is much slower than
RAM
1.3 Storage
Primary Storage (Sometimes
called Main Memory) refers
to the memory areas that the
CPU can access very quickly
(Cache, RAM and ROM).
Primary storage has the
fastest read/write speeds
and is mostly volatile.
Secondary Storage is non-volatile – it’s
where all data (operating systems,
applications and user files) are stored
when not in use (e.g. HDD, USB Flash
drive, SD card). Read/write speeds are
much slower compared to primary
storage.
Types of storage
Optical
CD (700MB), DVD(4.7GB), Blu-Ray(25GB)
Cheap per GB and portable. Can even be given away on magazines!
Prone to getting scratched (not durable) and is slower than magnetic or solid state
Use is declining
Magnetic
High capacity and reliable. HDDs are generally around 2TB at the moment
Portable versions of HDDs are useful for backing up and transporting large amounts of data
Sensitive to being dropped (i.e not durable)
Solid State
No moving parts (only uses memory chips, no spinning motors that are noisy/generate heat)
Fast, reliable and highly portable (light and small).
SD cards and USB Pen drives aren’t nearly as fast as SSDs, but still are very useful!