Primary memory

Q2. a)  Primary memory is of two basic type RAM and ROM.
Give difference between  ROM (Read Only Memory)  and  ROM (Random Access Memory) .

ROM (Read Only Memory)	RAM (Random Access Memory)
ROM is a Non-volatile Permanent memory.	RAM is a Volatile Temporary memory.
It holds the data even when the power is switched OFF.	It loses data when the power is switched OFF.
It stores the programs and data that do not need to be changed.	It stores the programs that are currently currently in use and always need to be changed.

b)  Give two  applications of ROM and RAM  memory.

Applications of ROM memory :

1.  ROM stores the Basic Input/Output System (BIOS).
2.  It stores factory settings and startup programs which is needed when the device is switched ON.

Applications of RAM memory :

1.  RAM is used to store the parts of Operating System.
2.  It stores data and programs currently in use.

Q3.  The two Primary Memory used in computers are RAM and ROM which are available in different types based on the technology used.

Identify  different types of RAM and ROM. 

⇒  The two main variants of RAM are : SRAM (Static RAM) and DRAM (Dynamic RAM)

⇒  The three main variants of ROM are : PROM (Programmable ROM), EPROM (Erasable Programmable ROM) and EEPROM (Electrically Erasable Programmable ROM)

Q4. a)  Describe the following  two types of RAM  memory.

1.  DRAM :

✬  DRAM stands for Dynamic Random Access Memory.

✬  It holds data by refreshing or re-charging it periodically. (1000 times per sec.)

✬  It contains a number of transistors and capacitors.

✬  Capacitors holds the data bits and Transistors acts like a switch to read and write data in the capacitors.

2.  SRAM :

✬  SRAM stands for Static Random Access Memory.

✬  It does not need to be refreshed or re-charged to hold data.

✬  It contains Flip-flop circuits that holds data bits as long as power is ON.

b)  Give two  advantages of DRAM over SRAM .

1.  DRAM is less expansive than SRAM.
2.  DRAM consumes less power than SRAM.
3.  DRAM has higher Storage capacity than SRAM.

c)  Give two  advantages of SRAM over DRAM .

1.  SRAM is much faster than DRAM.
2.  SRAM does not need to be refreshed to hold data.

Q5.  Describe the following  types of ROM  memory.

 PROM :

✬  PROM stands for Programmable Read Only Memory.

✬  The user can only store data or program using special devices (by applying high-voltage pulse).

✬  Once the program is written, it cannot be changed.

✬  Capacitors holds the data bits and Transistors acts like a switch to read and write in the capacitors.

 EPROM :

✬  EPROM stands for Erasable Programmable Read Only Memory.

✬  The user can erase and re-write data or programs using special devices (by shooting Ultra-violet light).

✬  When EPROM is used, its content can only be read.

 EEPROM :

✬  EEPROM stands for Electrically Erasable Programmable Read Only Memory.

✬  The user can read and write data or programs using electrical charge.

✬  So data stored in EEPROM can be easily modified. (Example : Pendrive)

Q6.  Describe  Cache. 

⇒  Cache is a very high-speed temporary memory, built using SRAM technology, placed between RAM and CPU.

⇒  It increases the CPU performance by holding frequently requested data and instruction for immediate use by CPU.

⇒  It is used to speed up and synchronize the main memory RAM with high-speed CPU.

⇒  When the CPU need to read memory, it will first check out the cache and then move to main memory RAM if the required data isn't there.

⇒  It is costlier than main memory RAM but economical than CPU registers.

Note : Cache means any area of storage used to quickly access frequently used data, other examples include web-cache, database cache, DNS cache, etc.

Secondary memory

Q7.  State different  categories of Secondary storage. ?

There are three main types of Secondary storage in a computer system :

1.	Magnetic storage device	It stores data on a magnetized medium, such as Magnetic tape, Floppy disks and Hard Disk Drives.
2.	Optical storage device	It stores data using Laser beam on optical media, such as Compact disk (CDs), DVD and Blu-ray disks.
3.	Solid state storage device	It stores data electronically with the controlled movement of electrons within NAND or NOR chips, such as Solid State Drive (SSD), Memory cards and USB memory sticks.

Q8.  Describe  how data is stored in Hard Disk Drive (HDD). 

⇒  HDD stores data in digital format by assigning magnetic charge on round Magnetic plates called Platters.

⇒  Each platter has its own Read-write Head to read and write data.

⇒  Data is stored on the platter in Concentric tracks and Sectors.

⇒  A Motor is used to rotate the platters around the spindle at a very high speed.

⇒  When data is requested to be stored on a particular area of a platter, the actuator arm moves the Read-write head to that track.

⇒  Read-write heads consist of electromagnets that are used to write data to or read data from the platters.

⇒  HDD uses data-cable (SATA / PATA) to receive or send data to the main memory RAM.

Q9. a)  Describe  how data is stored in Solid State Drive (SSD). 

⇒  SSD is a non-volatile re-writable memory that uses EEPROM technology.

⇒  SSD stores data by controlled movement of electrons within NAND or NOR chips.

⇒  The data is stored in millions of tiny transistors, arranged in a matrix of rows and columns within the chip.

⇒  At each intersection of the matrix, there is a floating gate and a control gate.

⇒  A positive charge on the control gate attracts the electrons from the channel into the floating gate. The dielectric tunnel oxide coating over the floating gate keeps the electrons trapped.

⇒  When charged, the floating gate has the value of 1 and a value of 0 when it isn’t, to store data.

⇒  It reads and writes data sequentially.

 Note : NOR device was first developed, which read data faster, but they are slower at writing data and do not store data efficiently.
NAND is the most common type of SSD called as Flash Memory. It is faster to write data and takes up significantly less space than NOR, which also makes it less expensive.  

b)  Give reasons  why SSD are better than HDD . (Advantages of SSD)

•  SSD do not have moving parts, so it do not generate heat and sound.
•  SSD stores data in chips, so it is very smaller in size and weightless.
•  SSD consumes less power than HDD.
•  SSD access data much faster than HDD.

c)  Give reasons  why SSD are not used in Servers . (Disadvantages of SSD)

•  SSD have limited Write cycle capacity.
•  SSD is expensive than a HDD.
•  SSD is available with small storage capacity (less than 160 GB) than a HDD.

Q10.  Identify  which type of storage device would be the most suitable for use in a web server  and justify your choice.

Type of storage : Hard Disk Drive (HDD)

Justification :

⇒  HDD is capable of handling more read/write request than SSD (has more longevity).

⇒  HDD is cheaper to buy for per unit of storage than solid state.

⇒  HDD is available with very high storage capacity than SSD, web server will likely need to store a lot of data.

⇒  No requirement for HDD to be portable, so moving parts does not matter.

Q11. a)  Describe  Dongle  with example.

Dongle is a small device that plugs into a computer and serves as an adapter to provide additional functionality, or security to enable the use of certain software.

Example :

• Software protection dongle.
• USB Wi-Fi adapters.
• Blue-tooth adapter to connect wireless Mouse.
• A Modem to connect Broadband Internet connection.

b)  Describe the use of  Flash memory as software protection Dongle. 

⇒  Flash memory (also known as Pen drive) could store a license key, the cryptographic algorithms and files that are needed to run a certain software.

⇒  Without this dongle, the software won’t work properly on a computer.

⇒  Hence, it prevents illegal or unauthorized use of software, and also prevents copying of software.

Q12.  Optical storage media like CD or DVD can be used to store data.

a)  Describe  how data is written (burnt) on the CD/DVD .

⇒  The data are stored on CD in a series of minute groves called pits in a spiral track.

⇒  The flat areas between two pits is called lands.

⇒  A Red or White laser (white is powerful than red laser) is used to write or burn the data on the surface of CD by creating lands and pits.

⇒  The non-reflective pit represents data bit ‘0’ and reflective land represents data bit ‘1’.

b)  Describe  how data is read from the CD/DVD .

⇒  The data is written in a series of non-reflective groves called pits and reflective flat surface called lands in a spiral track..

⇒  The CD-drive shines a Red laser beam on the surface of the CD to be absorbed by pits and reflected by lands.

⇒  The CD-drive converts the reflections into 1’s and 0’s to read the data.

Q13.  Give  difference between DVD and CD. 

⇒  DVD stands for Digital Versatile Disk, while CD stands for Compact Disk.

⇒  The lands and pits used to store data bits in DVD is much smaller than CD.

⇒  DVD use lasers with a shorter wavelength (650 nanometres) than CDs (780 nanometres). The shorter the wavelength of the laser light, the greater the storage capacity of the medium.

⇒  DVD can store more data (4.7 GB) than CD (700 MB).

⇒  DVD is made to store video files, while CD is made to store audio files.

⇒  DVD can be of single or double layered. Dual layer DVD can hold data (8.5 GB) twice the capacity of single layer.

⇒  In Dual layer DVD, two layers of a standard DVD are joined together with a semi-transparent polycarbonate spacer, and a very thin reflector.

⇒  In Dual layer DVD, reading and writing of the second layer is done by a red laser shifting the focus from first semi-transparent reflector to the second. layer.

Q14.  Give  difference between DVD-ROM and DVD-RAM. 

DVD-ROM :

1.  DVD-ROM stores data in a single spiral Track.
2.  DVD-ROM is Read Only Memory data cannot be errased to re-write.
3.  DVD-ROM access data Sequentially.

DVD-RAM :

1.  DVD-RAM stores data in multiple concentric circular Track.
2.  DVD-RAM can read and write data simultaneously at the same time (like Hard Disk).
3.  DVD-RAM access data directly in Random way.
4.  Programs can run from DVD-RAM like Hard disk.
5.  DVD-RAM has Re-writeable capacity 100 times than DVD-ROM (arround 100000 times).
6.  DVD-RAM can reliably store data upto 30 years (has great longevity).

Q15.  Describe  Blu-Ray Disk. 

⇒  Blu-ray disk uses Blue laser, with shorter wave length (405 nanometres instead of Red laser with 650nm) to read and write data over Optical media.

⇒  Blu-ray can store five times more data (around 25 to 50 GB) because its pits and lands are much smaller than normal DVD.

⇒  Blu-ray disks come with a secure encryption system which helps to prevent piracy and copyright infringement.

⇒  Blu-ray uses a single 1.1 mm thick polycarbonate disk to prevent Birefringence (light is Refracted into two separate beams causing reading errors).

Q16.  Give difference between  SSD /or/ Flash memory  and  CD-RW .

SSD or Flash memory	CD-RW
✬  Stores data in Semiconductor chips (or IC's).	✬  Stores data in Optical media.
✬  Direct transfer of data.	✬  Data need to be burnt before use.
✬  Plugs directly into the USB port.	✬  Requires a separate CD-drive.
✬  Data access is much faster than CD-RW.	✬  Slower data access speed than SSD.
✬  SSD do not have moving parts, so it do not generate heat and sound.	✬  CD-RW need to spin at a very high constant speed.
✬  SSD is expensive than CD-RW.	✬  CD-RW is cheaper than SSD.

Virtual Memory :

Q1. a)  What is  Virtual Memory ?

⇒  The Hard disk is partitioned to create Virtual Memory. It is ued to extend RAM memory.

⇒  It is created when a computer is running many processes at once and RAM is running low or out of space.

⇒  When RAM is full, the pages of data that are not currently in use are transfered from RAM to to Virtual Memory in secondary storage HDD/SSD.

⇒  It is a memory management technique of Operating System that creates an illusion of having a large physical memory RAM.

Virtual memory appears to exist as Main memory RAM although most of its data is held in Secondary memory Hard disk or SSD.

b)  What is the purpose of Virtual Memory?

⇒  To allow computer to process large amount of data beyond the capacity of RAM.

⇒  Enables the data held in RAM which is not currently in use by CPU, to be automatically moved to the hard disk.

⇒  It provides free space in RAM for other programs and data that need to be executed.

c)  A student is using video editing software. This process often requires the use of virtual memory.

Explain  why virtual memory is needed  for this purpose.

⇒  To allow computer to process large amount of data beyond the capacity of RAM required for video editing software.

⇒  It allows to extend the RAM capacity.

⇒  To prevent video editing software from freezing or crashing when the physical memory RAM is full.

Q2. a)  Describe  how Virtual Memory works. 

⇒  When RAM runs out of space, the OS moves data from the process that are not immediately needed for CPU out of the RAM, and stores them in virtual memory in HDD/SSD.

⇒  This action frees up the space on RAM and allows other new process to make use of it.

⇒  The area of the hard disk that stores the RAM image is called a Page file.

⇒  The OS moves the data back from virtual memory into RAM when the process is needed again called Swapping.

b)  Give advantages and disadvantages of Virtual Memory.

✬   Advantages : 

1. You can run more applications at once.
2. You can run larger applications with less storage capacity of RAM.
3. You don't have to buy large capacity expensive RAM.
4. No need to waste memory with data that isn't being used by CPU.

✬   Disadvantages : 

1. Using virtual memory makes a computer run slower.
   (As the processor has to wait while data is swapped between hard disk and RAM).
2. It takes more time to switch between applications.
3. Applications runs slower.
   (Because more and more data need to be swapped data between RAM and HDD/SSD leading to a very high rate of hard disk read/write head movements called Disk thrashing).
4. A point can be reached when execution of a process comes to a halt.
   (Because system gets so busy swapping data between RAM and HDD rather than executing the real process called Thrash point).

Cloud Storage :

Q1. a)  Describe  Cloud Storage. 

⇒  Cloud storage is a cloud computing model that stores data on remote third party servers.

⇒  The cloud storage system is owned and managed by a company that provides cloud-based services.

⇒  Multiple copies of same data is stored in many locations in more than one off-site server, rather than on an organization's own system.

⇒  It allows clients to access data, even if, any of its server goes through maintenance or repair called data redundancy.

b)  How you can use a Cloud storage?

⇒  To use cloud storage, you have to register and set up an account in cloud computing provider's website.

⇒  Then you could simply save your files via the internet using your unique username and password.

⇒  This ensures your data remains safe, secure and inaccessible to anyone else.

Q2.  What is meant by data redundancy and why it is important in clould operations?

⇒  Data redundancy is a condition created for a system in which the same data is held in multiple places.

⇒  It prevents loss of data; allows immediate access to the backed-up versions of data if any of its server becomes corrupted or unavailable.

Q3.  Give benefits and drawbacks of using Cloud storage.

✬   Benefits : 

1. Files could be accessed at any time from any device from anywhere in the world provided internet access is available.
2. The cloud storage system offers almost unlimited storage capacity.
3. No need to purchase and carry your offline storage devices.
4. Protects data against natural disaster and data loss due to human error.
5. Allows to recover data if the client's hard disk or backup device fails.

✬   Drawbacks : 

1. Clients may face problems in accessing or downloading their data/files if internet connection is slow or unstable.
2. It can be expensive to pay client's ISP (Internet Service Provider) for higher download/upload data transfer rate.
3. The potential failure of the cloud storage company could risk the loss of all backup data.

Q3.  Describe the following three  types of cloud storage. 

1)  Public cloud storage

⇒  A cloud storage system where the user's company and cloud storage provider are different companies.

⇒  Data can be accessed online by the user and anyone who the user authorizes.

⇒  The user's company doesn't need to maintain the cloud storage system.

2)  Private cloud storage

⇒  A cloud storage system where the user's company has their own internal cloud storage; data is stored in off-site servers connected through intranet.

⇒  Data is protected by the company's own firewall.

⇒  The responsibility of managing cloud storage lies on user's host company.

3)  Hybrid cloud storage

⇒  Hybrid cloud storage is a combination of Private and Public cloud storage system.

⇒  Data is be stored on the private cloud and data processing task for some less sensitive data is assigned to the public cloud.

⇒  It offers the security of a private cloud and the personalization of a pubic cloud.