Notes of central processing Unit & storage devices

1. Topic :-
1. CPU
2. ALU
3. CU
4. MU
Memory Devices
Primary Memory Devices( RAM,
ROM,PROM,EPROM,EEPROM
Secondary Memory Devices ( Hard disk , Solid
sate disk , DVD, CD, Optical Disk , Pen Drive )
Presented by-Pragati kachhi

2. Central Processing Unit
 The computer's central processing unit
(CPU) is the portion of a computer that
retrieves and executes instructions.

 The CPU is essentially the brain of a
CAD system.
 It consists of an arithmetic and logic unit
(ALU), a control unit, and various
registers.
 The CPU is often simply referred to as
the processor.

3.  Responsibilities:-
 The CPU, Central Processing Unit (or simply processor) is the main chip
in a computer responsible for carrying out all tasks.
 It's responsible for telling all the other components in a computer what to
do, according to the instructions it is given by the programs (software)
running on that computer.
 Gigahertz:-
 The clock speed measures the number of cycles your CPU executes per
second, measured in GHz (gigahertz).
 A “cycle” is technically a pulse synchronized by an internal oscillator, but for
our purposes, they're a basic unit that helps understand a CPU's speed.

4.  Main purpose:-
 The central processing unit (CPU) guides the computer through
the various steps of solving a problem.
 Data enters the computer through an input unit, is processed by the
central processing unit, and is then made available to the user
through an output unit.
3 major parts of CPU :-
1) Register Set
2) ALU
3) Control

5. Function :-
CPU is considered as the brain of
the computer.
 CPU performs all types of data
processing operations.
It stores data, intermediate results,
and instructions (program).
It controls the operation of all parts
of the computer.

6.  ALU ( Arithmetic Logical Unit ):-
 In computing, an arithmetic logic unit is a combinational digital circuit that
performs arithmetic and bitwise operations on integer binary numbers.
 This is in contrast to a floating-point unit, which operates on floating point
numbers.
 Instructions:-
 The register operands used by an instruction are specified
by fields of that instruction.
 ALU is used to calculate an arithmetic result, compute a
memory address, or perform a comparison for a branch.
The result of an arithmetic/logical instruction is written back
into the register file.

7.  Function :-
 The ALU performs simple addition, subtraction,
multiplication, division, and logic operations,
such as OR and AND.
 The memory stores the program's instructions and
data.

8.  Control Unit :-
 The control unit of the central processing unit regulates and integrates the
operations of the computer.
 It selects and retrieves instructions from the main memory in proper
sequence and interprets them so as to activate the other functional elements
of the system at the appropriate moment.
 The control unit is the main component of a central processing
unit (CPU) in computers that can direct the operations during
the execution of a program by the processor/computer.
 The main function of the control unit is to fetch and execute
instructions from the memory of a computer.

9. Functions:-
The functions of the control unit include the following.
•It directs the flow of data sequence between the processor and other devices.
•It can interpret the instructions and controls the flow of data in the processor.
•It generates the sequence of control signals from the received instructions or commands from the
instruction register.
•It has the responsibility to control the execution units such as ALU, data buffers, and registers in the
CPU of a computer.
•It has the ability to fetch, decode, handle the execution, and store results.
•It cannot process and store the data.
•To transfer the data, it communicates with the input and output devices and controls all the units of the
computer.

10.  Memory Unit :-
 A memory unit is the amount of data that the memory can
hold.
 Besides, we measure this storage capacity in terms of bytes.
Moreover, there are different units of memory as per the
requirement.
 Primary storage, or memory, means the space on your hard drive that is
briefly used for working space.
 This usually occurs in a chip.
 Memory consists of four types of memory chips RAM, ROM, CMOS and
flash drive .

11. Memory Devices ( Storage Devices )
 Primary storage, or memory, means the space on your hard drive that is
briefly used for working space.
 This usually occurs in a chip.
 Memory consists of four types of memory chips RAM, ROM, CMOS and
flash memory .
Memory is primarilyof two types:-
•InternalMemory −cachememoryand primary/main memory
•External Memory−magnetic disk / optical disk etc.

13.  CharacteristicsofMemoryHierarchyarefollowing whenwe go fromtop to bottom.
 Capacityin termsofstorageincreases.
 Costperbitofstoragedecreases.
 Frequencyof accessofthememory bytheCPU decreases.
 Access time bytheCPU increases.

14.  RAM:-
 A RAM constitutes the internal memory of the CPU for storing data, program and program result. It is read/write memory. It is called
randomaccessmemory(RAM).
 Since access time in RAM is independent of the address to the word that is, each storage location inside the memory is as easy to reach
asotherlocation&takesthesameamountof time.
 Wecanreachinto thememoryatrandom&extremelyfastbutcanalsobequiteexpensive.
 RAM is volatile, i.e. data stored in it is lost when we switch off the computer or if there is a power failure. Hence, a backup
uninterruptiblepowersystem(UPS)is oftenusedwithcomputers.
 RAMis small, bothin termsofitsphysicalsizeandin theamountofdataitcan hold.
 RAMis oftwotypes:-
 StaticRAM(SRAM)
 DynamicRAM(DRAM)

15.  Static RAM (SRAM):-
 The word static indicates that the memory retains its contents as long as power remains applied. However, data is lost when the power gets down due
to volatile nature.
 SRAMchips use a matrix of 6-transistors and no capacitors.
 Transistors do not requirepower to prevent leakage, so SRAMneed not have to be refreshed on a regular basis.
 Because of the extra space in the matrix, SRAM uses more chips than DRAM for the same amount of storage space, thus making the manufacturing
costs higher.
 Static RAMis used as cachememory needs to be very fast and small.
 Characteristic of Static RAM:-
 Long life.
 No need to refresh.
 Faster.
 Used as cache memory.
 Large size.
 Expensive.
 High power consumption.

16.  Dynamic RAM (DRAM):-
 DRAM, unlikeSRAM,must be continuallyrefreshed in order for it to maintain thedata.
 This is done byplacing thememory on a refresh circuit that rewrites the data several hundredtimes per second.
 DRAMis used for most system memory becauseit is cheap and small.
 All DRAMs are made up of memorycells. Thesecells arecomposed of one capacitor and one transistor.
 Characteristics of Dynamic RAM:-
 Short data lifetime
 Needs to be refreshed continuously
 Slower as comparedtoSRAM
 Used as RAM
 Smaller in size
 Less expensive
 Less power consumption

17.  Functions of RAM :-
 1.) Reading Files. This is also the work of RAM memory.
 2.) Temporary Storage. That program or files of the computer which have
been used, then RAM saves the data in a temporary way, which is the main
function of the computer RAM.
 3.) Loading Applications. Loading a software application is also the main
function of RAM.

18.  ROM:-
 ROMstands for Read Only Memory.
 Thememory from which wecan only read but cannot
write on it. This type of memory is non-volatile.
 Theinformation is stored permanently in such
memories during manufacture.
 A ROMstores such instructions that arerequired to
start a computer.
 This operation is referred to as bootstrap.
 ROMchips are not only used in the computer but also
in other electronic items like washing machine and
microwave oven.
 Features of ROM (Read-
Only Memory):-
 ROM is a non-volatile
memory.
 Information stored in ROM
is permanent.
 Information and programs
stored on it, we can only
read.
 Information and programs
are stored on ROM in
binary format.
 It is used in the start-up
process of the computer.

19.  Characteristics:-
 ROM information can be easily updated.
 ROM provides very large amounts of inexpensive Data storage.
 Data in ROM is Nonvolatile, that is , it remains there even without electrical
power.
 ROM chips are easily Swapped between different brands of computers.
 What is the purpose of ROM:-
 The main purpose of ROM is to store the commands needed to start the
computer. So that the computer system can be started.
 Read-Only Memory As the name suggests the data in this memory can
be read-only.
 Another main purpose of ROM is to update the firmware software of the
computer.

21.  MROM:-
 MROM stand for Mask Read Only Memory. It is also a type of ROM,
which was the first ROM hard wired device.
 MROM contains a software mask that is burned onto the chip during the
semiconductor design manufacturing process.
 MROMs are also known as masked ROMs, which are cheap.
 MROM is used by computer systems that keep running for a long time.

22.  2. PROM:-
 The full form of PROM is Programmable Read Only Memory.
 This means that a user can program data into the PROM only once.
 The feature of PROM is that the user can program any data according to him.
 The person who writes the program in the PROM is called the PROM programmer or PROM burner
 PROM never deletes the program itself. It means your programs are permanently saved in PROM.
 Once the data is programmed in the PROM, you cannot make any changes to it.
 Applications of PROM
 Some examples of devices that use PROM, which names are given below.
 TV Remote
 Mobile Phones
 Early Computer Bios
 Video game consoles
 Radio-Frequency Identification

23.  3. EPROM:-
 The full form of EPROM is Erasable Programmable Read Only Memory.
 This means that the EPROM memory chip has these features that you can erase the data of this
memory chip and program the new data again and you can erase the new data again if you want.
 Erasing EPROM data is not easy, it is difficult.
 The device whose EPROM data is to be erased, then the EPROM has to be ejected from that
device only then can the data in the EPROM be erased.
 Ultraviolet light has to be used to erase the data of EPROM and it takes about 40 minutes to
erase the data of EPROM.
 EPROM data can be erased and programmed by a professional who is also called a PROM
programmer or PROM burner.
 Applications of EPROM
 Some examples of devices that use EPROM, which names are given below.
 Modem
 Video Card
 Compact Flash
 Smart Memory
 Memory Stick
 Computer BIOS Chip

24.  4. EEPROM:-
 The full form of EEPROM is Electrically Erasable and Programmable Read Only Memory.
 This means that the EEPROM memory chip has this feature that you can easily erase the data of the
EEPROM memory chip and can also program new data easily.
 Erasing EEPROM data is easy compared to EPROM. Because there is no need to take it out of the device
to erase the data of the EEPROM memory chip.
 Whereas to delete the data of EPROM, the EPROM chip has to be removed from the device.
 To erase the data of EEPROM, electric power has to be used so that you can erase the data of EEPROM
according to you.
For example, if you want, you can erase the data of the entire EEPROM memory chip at once or if you
want, you can also erase and program the data of the EEPROM memory chip part by part.
 You can erase and program the data of the EEPROM memory chip 10000 thousand times.
 Applications of EEPROM:-
 Some examples of devices that use EEPROM, which names are given below.
 Computer Bios Chip
 Microcontrollers for Smart Cards

25. RAM ROM
RAM is a temporary storage. ROM is permanent memory.
RAM stores data in MBs. ROM stores data in GBs.
RAM is a Volatile memory. ROM is a Non-Volatile memory.
RAM used in normal operations.
ROM used for startup process of
computer.
Writing data is faster in RAM
memory.
Writing data is slower in ROM
memory.
Difference between RAM & ROM

27. Secondary Storage Devices
 Characteristics of Secondary
Memory
These are magnetic and optical
memories.
It is known as backup memory.
It is non-volatile memory.
Data is permanently stored even if
power is switched off.
It is used for storage of the data in the
computer.
Computer may run without secondary
memory.
Slower than primary memories
 This type of memory is also known
as external memory or non-volatile.
 It is slower than 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.
Contents of secondary memories
are first transferred to main
memory and then CPU can access
it. For example, disk, CD-ROM,
DVD, etc.

28. secondary storage devices include:
•Solid-state drives (SSDs).
•Hard disk drives (HDDs).
•Cloud storage.
•CD-ROM drives.
•DVD drives.
•Blu-ray drives.
•USB flash drives.
•SD cards.
•Floppy diskette.

29. Hard Disk
All primary computer hard drives are found inside a computer case and
are attached to the computer motherboard using an ATA, SCSI, or SATA
cable. Hard drives are powered by a connection to the PSU (power supply
unit).
What is hard disk:-
A hard drive is a a magnetic disk on which you can store computer data. The
term hard is used to distinguish it from a soft, or floppy disk. Hard disk holds more
data and is faster than floppy disks. In general, hard disks are less portable than
floppies, although it is possible to buy removable hard disks.

30. Hard Disk

32.  A hard disk typically works on the principle of simple
magnetism to store the data and information.
 A hard drive typically consists of a large plate that is usually
made up of a magnetic material and is known as a platter.
 The platter is usually constructed in a circular shape.
How does a hard disk store data?
Data is stored on a hard drive in binary code, using 1s and 0s.
The information is spread out on the magnetic layer of the disk(s)
and are read or written by the read heads that 'float' above the
surface thanks to the layer of air produced by the ultra fast rotation
of the disk.

33. Characteristics of Hard Disk:-
•The hard disk provides a large storage capacity. ...
•It is much faster than the floppy disk.
•It is the primary media for storing data and programs.
•It is more reliable than a floppy disk.
•Data stored on the hard disk is safer than the floppy disk.
Advantages of HDD:
•It has a large capacity for storing data
•It is much faster than optical disks like DVD’S
•It has Persistent storage
•HDD easily replaced and upgraded.
Disadvantages of HDD:
•It depends upon on moving parts
•The disk surface can be damaged easily.
•It consumes heavy power.
•It makes more noise.
•Its read/write speed is slower than RAM.

34. What Is an SSD?
1. SSDs got their name—solid state—because they use solid-state
devices under the hood.
2. In an SSD, all data is stored in integrated circuits. This
difference from HDDs has a lot of implications, especially in size
and performance.
3. Without the need for a spinning disk, SSDs can reduce to the
shape and size of a stick of gum (what’s known as the M.2 form
factor) or even as small as a postage stamp.
4. Their capacity—or how much data they can hold—varies,
making them flexible for smaller devices, such as slim laptops,
convertibles, or 2 in 1s. And SSDs dramatically reduce access time
since users don’t have to wait for platter rotation to start up.
5. SSDs are more expensive than HDDs per amount of storage (in
gigabytes (GB) and terabytes (TB)), but the gap is closing as SSD
prices decline at a faster pace that HDD prices year over year.

35. SSD Technology
A solid-state drive (SSD) :-
1. is a data storage device that
uses solid-state memory to
store persistent data.
1. SSDS do not have any moving
mechanical components,
which distinguishes them from
traditional magnetic disks such
as HDDs or floppy disks.
1. SSDs use NAND-based flash
memory or DRAM to store
data.
The problems with today's Hard
Disks?
1. Hard Disk Drives Processors
have increased in speed by
orders of magnitude over the
years.
2. But spinning hard disk drives
(HDD) have not.
3. Performance gap between how
fast processors demand data
and how quickly HDD responds.
4. HDD speed lags behind
processors because it is
constrained by physical
components.

37. DISSADVANTAGES OF SSD:-
1. They are more expensive than
traditional hard drives.
1. Recommend Said State Drives
They currently offer less
storage space than traditional
hard drives.
1. Solid State Other Slower Write
Speed on low-end Models
(MLC based types).
SSD APPLICATIONS:-
• Servers
• Hybrid SDD
• Desktop computers
• Laptops
• Ultrabook's
• HD Camcorders
• Smart Tv
• CCTV Digital Video Recorder (DVR)

38. Characteristics of SSD :-
•Fast Speed. SSDs have 100 times greater throughput and instantaneous
access times for quicker boot ups, faster file transfers, and overall snappier
performance than hard disk drives.
•Ultra-Light Weight.
•Great Durability.
•Sound of Silence.
•Low Power Consumption.
•Cool Running.
•Excellent Cost-Efficiency.

39. Basis SSD HDD
Stands for Solid State Drive Hard Disk Drive
Heat, Electricity and Noise
Less rotation required.
Uses less power.
Less heat or noise.
More heat generation.
More noise.
More electricity to rotate the platters.
Speed
SSD has lower latency
SSD has faster read/writes
SSD has supported more input-
output operations per second.
HDD supports fewer input-output
operations per second.
HDD has higher latency
HDD has longer read/write times
Components
SSD architecture has NO moving
parts.
HDD architecture has moving parts.
Defragmentation
Performance doesn’t care about
fragmentation.
Defragmentation is not compulsory
as in HDD.
The performance is not better and
the main reason is disk
fragmentation. We need frequent
defragmentation.
Weight Less in weight. Heavy in weight.

40. Optical Disk
An optical disk drive (ODD) uses a laser light to read
data from or write data to an optical disc. These
include CDs, DVDs, and Blu-ray discs. This allows
you to play music or watch movies using pre-
recorded discs.
CD = Compact Disk
DVD = Digital video disk

41. C D = Compact Disk
 compact disc (CD), a molded plastic disc containing digital data that is scanned by a laser beam
for the reproduction of recorded sound and other information.
 Since its commercial introduction in 1982, the audio CD has almost completely replaced the phonograph
disc (or record) for high-fidelity recorded music
CD-ROM (Compact Disk)The compact disc-CD was inverted in 1982 by two well known companies, Philips and
Sony. Initially it was an audio CD. It is a small optical disk on which data such as music, text, or graphic images
is intelliy encoded. CD contains data in the same way as the hard disk.A CD is a fairly simple piece of plastic about of an
inch (1.2mm) thick. The data is recorded by creating pits by a laser beam.
Types of Compact Disk:
1. CD-DA: Audio CD, Digital audio
2. Photo-CD: developed to hold digitized photograph and sound
3. Video-CD: Can hold around 70 min of video.
4. CD-R: (write once and read many)
5. CD-RW: Rewritable CD.

42. •CD-ROM (Compact Disk – Read Only Memory) − The data on these CDs are
recorded by the manufacturer. Proprietary Software, audio or video are released
on CD-ROMs.
•CD-R (Compact Disk – Recordable) − Data can be written by the user once on
the CD-R. It cannot be deleted or modified later.
•CD-RW (Compact Disk – Rewritable) − Data can be written and deleted on
these optical disksagain and again

43.  DVD (Digital Versatile Disk) :-
 DVD drives are replacing CD-ROM drives in
personal computer and as a medium for storing
computer programmers.
 DVD-ROM is an optical disc storage media
format that can be used for data storage, which
include movies with high video and sound quality.
 DVD-ROM is a non-volatile optical storage
medium similar to CD-ROM , which contain
computer data that cannot be erased or rewritten.
 DVD-RW stands for digital versatile disk
Rewritable.
 Allows up to 17 gigabytes of storage (from 4.7
GB to 17 GB).

44.  Pen Drive:-
 Pen drive is a portable memory device that
uses solid state memory rather than magnetic
fields or lasers to recorddata.
 It uses a technology similar to RAM, except
that it is nonvolatile. It is also called USB drive,
key driveor flash memory.
 To meet different needs, there are different
types of USB flash drives based on the ports,
respectively
 USB 2.0 flash drive
 USB 3.0 flash drive
 USB 3.1 flash drive
 and 3.2 drive.
 The biggest difference between them is the
price and speed.

45. S. D. cards
A secure digital card (SD card) is a small flash memory device designed to provide high-
capacity memory in a portable size.
A standard SD card measures 32mm x 24mm x 2.1mm and weighs approximately 2 grams,
whereas mini SD and microSD cards are physically much smaller but contain a similar capacity of
memory.
3 cards are as follows:
•(Full Size) SD – 32mm x 24mm
•Mini SD – 21.5mm x 20mm
•Micro SD – 15mm x 11mm
Each type of card has a memory capacity range, and these are:
•SD standard – Up to 2GB SD memory card using FAT 12 and 16 file
systems
•SDHC standard – over 2GB-32GB SDHC memory card using FAT32
file system
•SDXC standard – over 32GB-2TB SDXC memory card using exFAT
file system.

46. Blue Ray Disk Drive :-
 Blu-ray is an optical disc format designed to
display high definition video and store large
amounts of data. Blu-ray is the successor to
DVD.
 The standard was developed collaboratively by
Hitachi, LG, Matsushita (Panasonic), Pioneer,
Philips, Samsung, Sharp, Sony, and Thomson.
 Blu-ray aimed to answer DVD's shortcomings.
 It allows you to see more depth, a wider range of color shades, and
more image detail. DVD uses red laser technology.
 The Blu-ray Disc format uses blue laser technology and
sophisticated video compression to achieve high-definition video
playback on a standard DVD-sized disc.
 Comparing to a standard
DVD, it offers almost 5
times greater storage
capacity.
 However blue-violet rays
suffers from shorter
wavelength compared to
a red laser used by a
DVD player.

47. Floppy Disk
 Alternatively referred to as a floppy or floppy disk, a floppy diskette is a storage
medium capable of holding electronic data, like a computer file.
 The floppy diskette was created in 1967 by IBM as an alternative to buying hard drives,
which were extremely expensive at the time.
 The picture is an example of a 3.5" floppy diskette, one of the most commonly used floppy
diskettes, capable of storing 1.44 MB of data.
function of a floppy disk?
Floppy disks were used to store data and
back up important information.
Recording data onto a disk and storing the
disk was, at the time, the best way of
retaining information.
Advantages of a floppy disk :
•Small.
•Easy to carry.
•Cheap.
•Easy to transport and handle.
•Data on a floppy disk device can be write-protected from
being changed accidentally.
•Floppy disk can be used to transfer data from one
computer to another computer.
•Portable and inexpensive.

49. Cloud Storage
 In this fast-moving world it become necessary to store data on the cloud
storage.
 The biggest advantage of cloud storage is that we can store any type of data in
digital form on the cloud.
 Another advantage of cloud storage is that we can access data from anywhere,
anytime on any device.
 There are many cloud storage providers such as, Google Drive, Dropbox,
OneDrive, iCloud, etc.
 They provide free service for limited storage but if you want to store beyond the
limit, you have to pay.
 In this section, we will discuss what is cloud storage, uses of cloud
storage, and its architecture in detail.