Memory
Organization
Memory Organization
hello@edutap.co.in 1|Page http://www.edutap.co.in
Contents
1 Memory Organization ........................................................................................................................... 3
2 Memory Hierarchy ................................................................................................................................ 3
3 Memory Management .......................................................................................................................... 3
Register Memory........................................................................................................................... 3
3.1.1 Types and Functions of Computer Registers: ....................................................................... 3
Cache Memory .............................................................................................................................. 4
Primary Memory ........................................................................................................................... 4
3.3.1 Random Access Memory (RAM) ........................................................................................... 4
3.3.2 Read Only Memory (ROM) .................................................................................................... 4
Secondary Memory (Auxiliary Memory) ....................................................................................... 5
3.4.1 Secondary Storage Devices ................................................................................................... 6
3.4.2 Cloud Computing .................................................................................................................. 8
4 Memory Measurement ....................................................................................................................... 10
hello@edutap.co.in 2|Page http://www.edutap.co.in
1 Memory Organization
The computer memory holds the data and instructions needed to process raw data and produce
output. The computer memory is divided into large number of small parts known as cells. Each
cell has a unique address which varies from 0 to memory size minus one.
2 Memory Hierarchy
The memory is characterized on the basis of two keys factors; capacity and access time. The lesser
the access time, the faster is the speed of memory.
3 Memory Management
Register Memory
✓ Register memory is the smallest and fastest memory in a computer. A register temporarily
holds frequently used data, instructions, and memory address that are to be used by CPU.
3.1.1 Types and Functions of Computer Registers:
✓ General Purpose Register- These register store data and intermediate results during the
execution of a program
✓ Data Register – It is a 16-bit register, which is used to store operands (variables) to be
operated by the processor. It temporarily stores data, which is being transmitted to or
received from a peripheral device.
✓ Program Counter (PC) – It holds the address of the memory location of the next
instruction, which is to be fetched after the current instruction is completed.
✓ Instructor Register – It is a 16-bit register. It stores the instruction which is fetched from
the main memory. The Control Unit takes instruction from Instructor Register, then
decodes and executes it.
✓ Accumulator Register – It is a 16-bit register, which is used to store the results produced
by the system. For example, the results generated by CPU after the processing are stored
in the AC register.
✓ Address Register – It is a 12-bit register that stores the address of a memory location
where instructions or data is stored in the memory.
✓ Memory Data Register- The data register (MDR) is the register of a computer’s control
unit that contains the data to be stored in the computer storage (e.g RAM) or the data
after a fetch from the computer.
✓ Memory Address Register- MAR holds the address of the next memory location where
the next instruction to be executed.
✓ I/O Address Register – Its job is to specify the address of a particular I/O device.
✓ I/O Buffer Register – Its job is to exchange the data between an I/O module and the CPU.
hello@edutap.co.in 3|Page http://www.edutap.co.in
Cache Memory
✓ Cache memory is a type of memory used to hold frequently used data. Cache memory is a
very high speed semiconductor memory, which can speed up the CPU.
✓ It act as the buffer between the CPU and the main memory.
✓ Once the data is stored in cache, it can be used by accessing the cached copy rather than
recomputing the original data.
✓ Cache memory provides backup storage for instructions and data that are not currently being
used by the processor. Cache memory is faster to access than RAM and ROM, making it ideal
for temporarily storing frequently accessed instructions and data to improve the overall
performance of the system.
Primary Memory
✓ Primary memory is also called as the main memory or internal memory of the computer as
it communicates directly with the CPU.
✓ It holds only those data and instruction on which computer is currently working. Its generally
made up of semiconductor device.
✓ It is divided into two subcategories: RAM and ROM
3.3.1 Random Access Memory (RAM)
✓ RAM performs both read and writes operations on memory. It stores data for temporally.
If power failures happened in systems during memory access then you will lose your data
permanently. So, RAM is a volatile memory.
✓ RAM categorized into following types.
3.3.1.1 Dynamic RAM
✓ Dynamic Random-Access Memory (DRAM) is a type of random-access memory used
in computing devices. It is made up of memory dell where each cell is composed of
one capacitors and one transistors.
✓ DRAM must be constantly refreshed, or it loses its contents. This type of memory is
more economical.
3.3.1.2 Static RAM
✓ Static Random-Access Memory (SRAM) is a type of RAM that holds data in a static
form, i.e., as long as the memory has power. SRAM does not need to be refreshed
periodically.
✓ It uses multiple transistor for each memory cell and does not use capacitor
✓ SRAM often uses cache memory due to its high speed.
3.3.1.3 Synchronous Dynamic RAM
✓ A type of DRAM that can run at much higher clock speeds.
3.3.2 Read Only Memory (ROM)
✓ ROM is a type of non-volatile memory.
✓ ROM is the memory from which we can only read. However the data stored in these chips
is either unchangeable or requires a special operation to change.
✓ The information is usually stored permanently in such memories during manufacture. A
ROM stores the instructions that are required to start a computer. This operation is
hello@edutap.co.in 4|Page http://www.edutap.co.in
referred to as bootstrap. ROM chips are not only used in the computer but also in other
electronic items like washing machines and microwave oven.
✓ There are four basic types of ROM:
3.3.2.1 Masked Read Only Memory (MROM)
✓ The first very ROMS were very hard-wired devices that contained a pre-programmed
set of data or instructions. These kinds of ROMs are known as Masked ROMs which
are inexpensive.
3.3.2.2 Programmable Read Only Memory (PROM)
✓ PROM is read-only memory that can be modified only once by a user. The user buys
a blank PROM and enters the desired contents using a PROM program. It can be
programmed only once and is not erasable.
3.3.2.3 Erasable Programmable Read Only Memory (EPROM)
✓ It is similar to PROM, but EPROM can be erased by exposing it to ultra-violet light. It
is also known as Ultra Violet Erasable Programmable ROM (UVEPROM).
✓ During programming, an electrical charge is trapped in an insulated gate region.
3.3.2.4 Electrically Erasable Programmable Read Only Memory (EEPROM)
✓ EEPROM is programmed and erased electrically. It can be erased and reprogrammed
about ten thousand times. Both erasing and programming take about 4 to 10 ms
(millisecond). In EEPROM, any location can be selectively erased and programmed.
✓ EEPROMs can be erased one byte at a time, rather than erasing the entire chip.
Hence, the process of reprogramming is flexible but slow.
Flash Memory
It is a kind of semiconductor based non volatile rewritable memory used in digital camera, mobile
phone, printer etc. Flash Memory is an example of quite recent type of storage technology known
as solid device.
Solid state devices
These are regarded as being robust and reliable because they have no moving parts with the data
stored in the semiconductor chips, this technology already exists in the forms of flash memory used
to store the Basic Input/Output system (BIOS) of a motherboard.
Secondary Memory (Auxiliary Memory)
✓ The main memory is very small and volatile in nature. To overcome these issues, another
memory is used in the computer system called as Secondary memory or auxiliary memory or
external memory.
✓ It is slower and cheaper than the main memory. These are used for storing data/information
permanently.
✓ CPU directly does not access these memories, instead they are accessed via input-output
routines.
hello@edutap.co.in 5|Page http://www.edutap.co.in
✓ The contents of secondary memories are first transferred to the main memory, and then the
CPU can access it. For example, disk, CD-ROM, DVD, etc.
3.4.1 Secondary Storage Devices
✓ These are the hardware devices that can hold information. These can either be external
or internal.
✓ Following are different types of Secondary storage devices.
3.4.1.1 Magnetic Storage Devices
✓ It is the manipulation of magnetic field on a medium in order to record data, audio or
video.
1. Floppy Disk/ Diskette
✓ Floppy disk is composed of a thin, flexible magnetic disk sealed in a square plastic carrier.
1 1
✓ Floppy Disks come in three basic sizes: 8-inch, 5 -inch and 3 -inch.
4 2
2. Zip Disks
✓ An advanced version of the floppy disk is known as Zip Disks. It was developed by Iomega.
Zip disks are available in 100 and 250-MB and 750 MB capacities and they are used to
store, share and back up large amounts of data.
3. Magnetic Tape
✓ Magnetic Tape was often used for digital data storage, because of its low cost and ability
to store large amounts of data.
✓ Its relative slowness and unreliability compared to other data storage solutions has
resulted in it now being largely abandoned as a media.
4. Hard Disk Drive
✓ It is a non-removable storage device containing magnetic disks or platters rotating at high
speeds. The hard drives store data in segments of concentric circles. It may spin at 5,400
to 15,000 RPM.
✓ It is a non-volatile storage device that can be modified or deleted multiple times without
any problem.
✓ HDD stands for Hard Disk Drive. HDD is also known as Hard disk, Hard drive, or Fixed disk.
Most computers and laptops have HDDs as their secondary storage device. HDDs are also
capable of storing operating system, large system files and are found in desktops, mobiles,
and consumer electronics.
5. Winchester disk
✓ It is also known as Winchester drive or Winchester disk drive, is an early form of hard disk
drive (HDD) technology that revolutionized data storage in computers. A Winchester disk
is a Disk Stack. The term Winchester comes from an early type of disk drive developed by
IBM that had 30MB of fixed storage and 30MB of removable storage.
6. Tape Cassette
hello@edutap.co.in 6|Page http://www.edutap.co.in
✓ It is also known as a music cassette. It is a rectangular flat container in which the data is
stored in an analog magnetic tape. It is generally used to store audio recordings.
Disk formatting
It is the process of configuring data-storage devices like hard drives, floppy disks, and flash drives for
initial usage or when additional storage space is needed. Formatting a disk erases all existing files on
it, making it ready for new data to be stored.
Formatting Description Performer Data Impact
Process
Low-level Involves marking cylinders and tracks Hard disk Erases all data on the
Formatting on a blank hard disk and dividing tracks manufacturers hard disk, making data
into sectors with sector markers. recovery impossible.
Partitioning Divides the hard disk into one or more Users Affects disk
regions called partitions. performance.
High-level Involves writing file system information, Users Erases the hard disk
Formatting cluster size, partition label, etc., for a and reinstalls the
newly created partition or volume. operating system.
3.4.1.2 Optical Storage Device
✓ It is the type of storage device in which data is written and read with a laser.
1. Compact Disc (CD)
✓ A compact disc is a portable storage medium that can be used to record, store data in
digital form. Its most popular and least expensive type of optical disc. A CD is capable of
being used as a data storage device along with storing of digital audio.
✓ CD is categorised into three main types as follows:
• CD-ROM : Compact Disc Read-Only Memory can be read but can’t change or delete
it.
• CD-R: Compact Disc Recordable are write once.
• CD-RW: Compact Disc Rewritable can be written and erased many times.
2. Digital Video Disc/ Digital Versatile Disc (DVD)
✓ DVDs offer higher storage than CDs while having same size.
✓ Depending upon the disc type DVD can store several GB of data (4.7-17.8GB). A Single
Layer DVD can hold 4.7 GB and a Dual Layer DVD can hold 8.5 GB of data.
✓ DVD is categorised into three main types as follows:
• DVD-ROM : DVD Read-Only Memory can be read but can’t change or delete it.
• DVD-R: DVD Recordable are write once.
• DVD-RW: DVD Rewritable can be written and erased many times.
hello@edutap.co.in 7|Page http://www.edutap.co.in
3. Blu-ray Disc
✓ The upgraded version of CD and DVDs and drives are the Blu-ray discs. Blu-ray refers to
the blue laser used to read the disc which allows the information to be stored at a greater
density.
✓ The Maximum capacity of BD disc is 25GB if single layer and 50 GB if dual layer.
✓ The variation in the format includes BD-ROM(Read only), BD-R(BD Recordable), BD-
RW(Rewritable), BD-RE(Rewritable)
Throughput
In the context of data storage and transfer, throughput refers to the rate at which data can be read from
or written to a memory storage device within a given unit of time. It measures the efficiency and speed of
data transfer between the storage device and other components of a computer system, such as the central
processing unit (CPU) or random access memory (RAM).
Throughput is typically measured in units such as bytes per second (B/s), kilobytes per second (KB/s),
megabytes per second (MB/s), or gigabytes per second (GB/s), indicating the amount of data that can be
transferred in one second.
Higher throughput values indicate faster data transfer rates and better performance of the storage device.
3.4.1.3 Solid State Storage
1. USB Flash Drives
✓ USB Flash drives are small, ultra-portable storage device. USB refers to the USB
connection that allows users to plug the device into the USB port of a computer. They are
often referred to as pen drives, thumb drives, or jump drives. Mostly they have a storage
capacity from 8 GB to 64 GB.
2. SD Card
✓ It is known as a Secure Digital Card. It is generally used with electronic devices like phones,
digital cameras, etc. to store larger data. It is portable and the size of the SD card is also
small so that it can easily fit into electronic devices. It is available in different sizes like
2GB, 4GB, 8GB, etc.
3. Memory Card
✓ It is generally used in digital cameras. printers, game consoles, etc. It is also used to store
large amounts of data and is available in different sizes. To run a memory card on a
computer you require a separate memory card reader.
3.4.2 Cloud Computing
✓ Cloud computing is a broad term encompassing various services and technologies that
utilize hosted services over the Internet. Nowadays, secondary memory has been
upgraded to virtual or cloud storage devices. We can store our files and other stuff in the
cloud and the data is stored for as long as we pay for the cloud storage.
hello@edutap.co.in 8|Page http://www.edutap.co.in
3.4.2.1 Cloud Computing Services
✓ Cloud computing services can be categorized into the following types:
• Infrastructure as a Service (IaaS): In the IaaS model, virtualized infrastructure is
provided and managed by external cloud providers for businesses. This includes
services such as automated backup, recovery, and other policy-driven operations.
• Software as a Service (SaaS): SaaS involves delivering software applications over
the Internet based on demand and subscription basis. Common examples of SaaS
include Microsoft Office 365, Oracle CRM, and Marketo.
• Platform as a Service (PaaS): PaaS offers an on-demand environment for
developing, testing, delivering, and managing software applications. Key players
in the PaaS domain include Bluemix, CloudBees, and Salesforce.com.
Cloud Storage
• Cloud Storage is a specific aspect of cloud computing. Cloud storage services provide scalable
and reliable storage solutions without the need for users to manage physical hardware.
• Cloud storage is like having a virtual hard drive that you can access from anywhere with an
internet connection. Instead of storing your files, photos, or videos on your computer's hard
drive or a physical storage device like a USB drive, you can store them securely on servers
maintained by a cloud storage provider.
3.4.2.2 Types of Cloud Deployments
✓ Cloud deployments are categorized based on an organization's ability to manage and
secure assets. There are three primary types:
• Public Cloud: Public clouds are managed by third-party providers who offer
services over the Internet to the general public. Public clouds are designed to
serve multiple users rather than a single customer.
• Private Cloud: Private clouds consist of distributed systems that operate on a
private infrastructure, providing users with dynamic provisioning of computing
resources.
• Hybrid Cloud: Hybrid clouds are created by combining the capabilities of both
public and private clouds. They are also known as heterogeneous clouds due to
their mixed nature.
Some Next Generation Memories
• FeFET or FeRAM A next generation ferroelectric memory.
• Nanotube RAM In R & D for years, nanotube RAM is targeted to displace DRAM. Others are
developing carbon nanotubes and next generation memories on the same device.
• Spin Orbit Torque MRAM(SOT-MRAM)- A next generation MRAM targeted to replace SRAM.
hello@edutap.co.in 9|Page http://www.edutap.co.in
4 Memory Measurement
The data is measured in term of bits in the memory.
Name Size
1 bit Single digit 0 or 1
1 nibble 4 bits
1 byte 8 bits
1 Kilobyte (KB) 1024 Bytes
1 Megabyte (MB) 1024 KB
1 Gigabyte (GB) 1,024 MB
1 Terabyte (TB) 1,024 GB
1 Petabyte (PB) 1,024 TB
1 Exabyte (EB) 1,024 PB
1 Zetta byte (ZB) 1,024 EB
1 Yotta Byte (YB) 1,024 ZB
1 Brontobyte (BB) 1,024 YB
1 Geop Byte 1,024 BB
hello@edutap.co.in 10 | P a g e http://www.edutap.co.in
