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Main » 2013 » August » 11 » PRIMARY STORAGE
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PRIMARY STORAGE
Primary storage is also called internal storage or memory. It is used to store programs and data
currently being processed by CPU. Primary storage circuits like light bulbs need electricity to
stay on. If the power to the computer is turned off, all the circuits will turn off and all data in
primary storage will be lost. When computer is turned back on the data will not reappear. The
data is lost forever. Because of this characteristics primary storage is called volatile storage. This
type of primary storage is called RANDOM ACCESS MEMORY or RAM. RAM is the main
type of primary storage used with computers and it is volatile.
ROM – Many computers have another type of primary storage called ROM – Read Only
Memory. ROM is non-volatile storage. This means that when the power to the computer is
turned off, the content of the ROM is not lost. ROM can store preset programs that are always
put by computer manufactures. When you turn on a PC, you will usually see a reference on
BIOS (Basic Input output System). This is part of the ROM chip containing all the programs
needed to control the keyboard, monitor, disk drive and so on.
There are different types of ROM, including PROM EPROM and EEPROM.
PROM – Programmable Read Only Memory – In this type of ROM, data or program can be
stored once in PROM but never changed.
EPROM – Erasable Programmable Read Only Memory – In this type of ROM, data or program
can be erased by removing the device and exposed it to ultraviolet light.
EEPROM – Electrically Erasable Programmable Read Only Memory – data or program can be
completely erased using a special device and new programs or new data can be stored in it.
The Use of Primary Storage (RAM)
Main Memory has several uses:
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- Input area – where the data is stored when it is read into CPU, awaiting processing.
- Operating system – controls the operation of the computer.
- Working storage – where calculations are performed and data is stored temporarily.
- Output area where the information is stored prior to output. Both the input and output areas
are buffer.
- Application program area – where the user program is held.
The Use of Main Memory (RAM)
Input Area
Operating System
Output Area Application area (Program)
Working storage area
2.4 SECONDARY STORAGE
Secondary Storage is an optional attachment, which is cable –connected to the CPU. Secondary
is nonvolatile. Any data or programs stored in secondary storage stays there, even with the
computer power turned off, unless someone purposely erases them. Secondary storage is a
permanent from of storage.
Difference between ROM and RAM
ROM RAM
ROM is nonvolatile RAM is volatile
ROM is cheaper than RAM RAM is very expensive
The contents of ROM are always known
and can be verified
The contents are not known
ROM can not be updated or corrected RAM can be updated and corrected
ROM serves as permanent data storage RAM can serve as temporary data storage
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Difference between Primary and Secondary Storage
Primary Secondary
Primary storage/memory is also called
Internal or main storage. High speed
Secondary storage or memory is also called
External or auxiliary storage. Low speed
It is very expensive It is not expensive as primary storage
It holds data or programs temporary It holds data or programs permanently
It holds programs and data in current use in
CPU
It holds program or data that will still be
used in primary storage
It is faster than secondary It is not fast as primary
It holds less data It holds large volume of data or files
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