Department Of Computer Application (BBA)

Dr. Rakesh Ranjan

BCA Sem - 2
Memory System

Computer memory is any physical device capable of storing

information temporarily, like RAM (random access memory), or
permanently, like ROM (read-only memory). Memory devices
utilize integrated circuits and are used by operating
systems, software, and hardware.

Memory is technically any form of electronic storage, it is used

most often to identify fast, temporary forms of storage. If our
computer's CPU had to constantly access the hard drive to
retrieve every piece of data it needs, it would operate very
slowly. When the information is kept in memory, the CPU can
access it much more quickly. Most forms of memory are intended
to store data temporarily.

Application Of memory

 The computer loads data from read-only memory (ROM) and

performs a power-on self-test (POST) to make sure all the
major components are functioning properly. As part of this test,
the memory controller checks all of the memory addresses
with a quick read/write operation to ensure that there are no
errors in the memory chips. Read/write means that data is
written to a bit and then read from that bit.
 The computer loads the basic input/output system (BIOS)
from ROM. The BIOS provides the most basic information about
storage devices, boot sequence, security, Plug and Play (auto
device recognition) capability and a few other items.
 The computer loads the operating system (OS) from the hard
drive into the system's RAM. Generally, the critical parts of
the operating system are maintained in RAM as long as the
computer is on. This allows the CPU to have immediate access
to the operating system, which enhances the performance and
functionality of the overall system.
 When we open an application, it is loaded into RAM. To
conserve RAM usage, many applications load only the essential
parts of the program initially and then load other pieces as
needed.
 After an application is loaded, any files that are opened for use
in that application are loaded into RAM.
 When you save a file and close the application, the file is
written to the specified storage device, and then it and the
application are purged from RAM.
In the list above, every time something is loaded or opened, it
is placed into RAM. This simply means that it has been put in
the computer's temporary storage area so that the CPU can
access that information more easily. The CPU requests the data
it needs from RAM, processes it and writes new data back to
RAM in a continuous cycle. In most computers, this shuffling
of data between the CPU and RAM happens millions of times
every second. When an application is closed, it and any
accompanying files are usually purged (deleted) from RAM to
make room for new data. If the changed files are not saved to
a permanent storage device before being purged, they are lost.
 Cost & Speed capacity

Memory May be categories as

Volatile vs. non-volatile memory

Volatile memory is memory that loses its contents when the
computer or hardware device loses power. Computer RAM is an
example of volatile memory. It is why if your computer freezes or
reboots when working on a program, we lose anything that hasn't
been saved.
Non-volatile memory, sometimes abbreviated as NVRAM, is memory
that keeps its contents even if the power is
lost. EPROM,EEPROM,FLUSH ROM is an example of non-volatile
memory.

All the Secondary memory comes under Non-Volatile Memory

Primary Vs Secondary Memory

1) Primary Memory (Main Memory)(Electronic memory)

It is also referred to as Main Memory. It is volatile. The reason

behind is, Primary memory holds only those data and
instructions on which the computer is currently working i.e. it
does not store the data permanently.

 It stores the operating system and data required to run

the computer.
 It is a limited capacity memory and data or information is
lost when power is switched off. Primary Memory is
generally constructed with a semiconductor device.
 Registers are much faster than these memories but it is
faster than secondary memory.
 It contains all the data and instructions that are required
to be processed.

It is further divided into two subcategories RAM and

ROM.

1. RAM (Random Access Memory)

t is Random Access Memory because of the random selection

I

of memory locations. It performs both read and writes

operations on memory. It stores data temporarily.
If power failures happen in the system during memory access
then you will lose your data permanently. So, RAM is a volatile
memory.

RAM categorized into following types:

a. SRAM
b. DRAM
c. SDRAM
d. DDR RAM
e. DDR2 RAM
f. DDR3 RAM
g. DDR4 RAM

2. ROM (Read Only Memory)

ROM offers huge types of standards to save data as it is a

permanent memory location. But it works with the read-only
operation. whenever power failure occurs during the ROM
memory work in computers then no data lose happens.

 It is Used where the programming requires no change and

also in embedded systems or.
 It is Used in peripheral devices and calculators.

Types of Read Only Memory (ROM)

a. PROM (Programmable read-only memory)

b. EPROM (Erasable Programmable read only memory)
c. EEPROM (Electrically erasable programmable read only
memory)
d. Flush ROM
2)Secondary Memory
Primary memory has limited storage capacity and is volatile.
Secondary memory overcome this limitation by providing
permanent storage of data and in bulk quantity. Secondary
memory is also termed as external memory and refers to the
various storage media on which a computer can store data and
programs. The Secondary storage media can be fixed or
removable. Fixed Storage media is an internal storage medium
like hard disk that is fixed inside the computer. Storage medium
that are portable and can be taken outside the computer are
termed as removable storage media.
Fixed and Removable Storage

Fixed Storage

A Fixed storage is an internal media device that is used by a

computer system to store data, and usually these are referred to
as the Fixed Disks drives or the Hard Drives.
Fixed storage devices are literally not fixed, obviously these can
be removed from the system for repairing work, maintenance
purpose, and also for upgrade etc. But in general, this can’t be
done without a proper toolkit to open up the computer system to
provide physical access, and that needs to be done by an
engineer.
Technically, almost all of the data i.e. being processed on a
computer system is stored on some type of a built-in fixed
storage device.
Types of fixed storage:
 Internal flash memory (rare)
 SSD (solid-state disk) units
 Hard disk drives (HDD)
Removable Storage-
A Removable storage is an external media device that is used by
a computer system to store data, and usually these are referred
to as the Removable Disks drives or the External Drives.
Removable storage is any type of storage device that can be
removed/ejected from a computer system while the system is
running. Examples of external devices include CDs, DVDs and
Blu-Ray disk drives, as well as diskettes and USB drives.
Removable storage makes it easier for a user to transfer data
from one computer system to another.
In a storage factors, the main benefit of removable disks is that
they can provide the fast data transfer rates associated with
storage area networks (SANs).

Types of Removable Storage:

 Optical discs (CDs, DVDs, Blu-ray discs)
 Memory cards
 Floppy disks
 Magnetic tapes
 Disk packs

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