Computer memory is the medium of storage for the computer
system. The computer memory stores data, information, programs in itself for
use.
These are 2 main types of computer memory. They are:-
i.
Internal/Main/Primary memory
ii. External/Auxiliary/Secondary
Memory
Internal Memory: this memory is considered to be part of the
Central Processing Unit (CPU). It stores data and information that are needed
for the immediate execution and programs currently run are held in it.
Generally, the large capacity of the internal memory makes a computer to be
extra powerful by being able to accommodate and run multiple programs during
simultaneous execution and assessment. Also, it increases the speed of program
execution.
The
internal memory is divided into two parts, they are;-
-
random access memory (RAM)
-
read only memory
(ROM)
(1) Random Access Memory;- form the larger
part of the internal memory inmost computers. This is the part that users have
access to because it is ion this part that currently run programs are been held
temporally until they are transferred (saved) into the external memory, they
are liable to get lost except there is provision for backup facility on the
computer.
(2) Read Only Memory;- is a permanent (non
volatile) memory that holds important frequently used programs which are made
available for each time they are needed. Programs stored inside the ROM cannot
be altered by the user(s) by any means, thereby rendering security (protection)
for such programs (because users do not have access to it (ROM) rather than
making use of it when required). For example, the operating system is kept in
the ROM.
Difference between RAM and ROM
|
s/n
|
Random Access
Memory
|
Read Only Memory
|
|
1
|
Information can be written on a RAM
|
Information cannot be written on a ROM
|
|
2
3
|
Information can be retrieve
from a RAM
RAM has no fixed size
|
Information can not be retrieve from a ROM
ROM has a fixed
size
|
|
4
5
|
In formation are not permanent
Application programs are processed through the RAM
|
Information are permanent in ROM
ROM contains system programs, which is responsible for
booting processing of the computer system as well as the configuration of the
system.
|
The External Memory:
There are some programs which need not
to be kept in the internal memory because they are not often needed for use,
although the internal memory cannot even contain them since some of them are
very are large. This set of program are stored in the external memory (but will
be loaded in the internal memory when needed for execution) which is not part
of the CPU but different on its own as component though it is connected on-line
to the CPU. It is permanent storage medium; therefore stands as effective
backup in case of any damage or loss of data in the RAM of the internal memory.
It has larger memory capacity than the internal memory.
Common examples of external devices are:-
i.
Magnetic disk,
ii.
Magnetic tapes,
iii.
Floppy disk(diskette),
iv.
Hard disk,
v.
CD-ROMs, etc.
The memory capacities (size) of these devices are measured in
the unit known as byte. A byte refers to the number of bit required to
represent each character on the computer and it’s generally equal to eight bits
i.e. 1byte=8bits (bits are in 0s and 1s) by extension we can say I
kilobyte=1000bytes, though in the real sense of it, it 1024 bytes that makes
1kb
One
Kilobyte or 1kb = 1000bytes
One
Megabyte or 1Mb=1000000bytes
One
Gigabyte or 1 GB = 1000, 000,000bytes
Different between
Internal and External Memory
|
S/N
|
Internal Memory|
|
External Memory|
|
|
1
2
3
4
5
|
It is very fast in its operation
It is very expensive
It is within the computer Central Processing Unit(CPU)
It is very volatile(Temporal)
It is limited in capacity for storage
|
It is slow its operation
It is not expensive
It is not within the Central Processing Unit(CPU)
It is not volatile but permanent
It has unlimited for storage
|
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