Chapter 5: Computer System | NEB Notes

Short Answer Questions

1. What do you understand by storage media? Why CDROM are more reliable than the floppy diskettes?

Storage media is the secondary memory of the computer. It is used for storing large amount of data for longer period of time. It is also used for transferring data from one computer to another. It is usually cheaper, slower and used in larger storage capacity. It is not directly accessible to CPU. It requires primary memory for its operations. Example: Hard disk, DVD, CD, Pen drive. Different types of storage media used are: magnetic memory, optical memory and flash memory.

Reliability of CDROM than Floppy Diskettes

CDROM are more reliable than the floppy diskettes due to following reasons:

  • Data corruption rate is higher in floppy disk, due to use of magnetic head, which is directly touch on Mylar plastic plate during read/ write data on floppy disk. But CD ROM does not have.
  • CD ROM does not have any mechanical read/write heads to rub against the disk surface. This makes CD ROM more reliable storage medium than floppy disk.
  • CD ROM has very high storage capacity (About 700 MB), whereas floppy diskettes has very low (About1.44 MB), due to high storage capacity of CD ROM, it is very useful to carry software from one computer to another.
  • CD ROM is relatively cheaper than floppy disk, cost per bit. (Cost of CD ROM is Rs. 10-15 and floppy diskette is Rs. 35.)
  • Due to use of sophistically technology in CD ROM; using Laser to read and write, it is much durable than floppy disk.

The access time of data and information stored in CD-ROM is faster than floppy disk, what’s why more and more computer users are liked to use CD ROM than floppy disk.


2. Define the term computer peripheral. Discuss about different types of printers with their merits and demerits.

Computer peripherals are the external or internal devices that are connected to the computer. It includes external devices like keyboard, monitor, speaker and internal devices like DVD-ROM, MODEM. Different types of printers are:

  • Impact printer
  • Non-impact printer

 Impact printer

In this type of printer, printing is done by physically touching the printing material. It uses mechanical method for printing. It use ink ribbon for printing. It is rarely used at present. Example: Dot matrix printer, Daisy wheel printer, Line printer.

Merits of impact printer:

  • It is cheaper.
  • It can print multiple copies at a same time by using carbon paper.

Demerits of impact printer:

  • It is noisy.
  • It is slow for printing.
  • It has low printing quality.
  • It is not appropriate for printing graphics.
  • It is usually single colored.

Non-impact printer

In this type of printer, printing is done by spraying liquid or powder ink without touching the printing material. It uses either electrostatic or electromagnetic mechanism for printing. It is commonly used at present. Example: Inkjet printer, Laser printer.

Merits of impact printer:

  • I It produces low noise.
  •  It is faster for printing.
  • It has better printing quality.
  • It is appropriate for printing graphics.
  • It can be single or multiple colored.

Demerits of impact printer:

  • It is expensive.
  • It cannot print multiple copies at a same time.

3. Write the importance of primary and secondary storage in a computer system.

Importance of Primary and Secondary Storage in a Computer System:

  • Primary memory is used for storing data and instructions during processing. It is the only memory which is directly accessible to CPU. It is the main memory of the computer. A computer cannot be operated without primary memory. It is usually expensive, faster of read/write operation and used in small storage capacity. Example: RAM, ROM, Cache Memory.
  • Secondary memory is used for storing large amount of data for longer period of time. It is also used for transferring data from one computer to another. It is the additional memory of the computer. It is usually cheaper, slower and used in larger storage capacity. It is not directly accessible to CPU. It requires primary memory for its operations. Example: Hard disk, DVD, CD, Pen drive.

4.  Distinguish between the terms ‘Hardware’, ‘Software’ and ‘Firmware’.

  • Hardware

Hardware is the physical component of the computer. Without hardware software can’t work. It includes input devices, output devices, processing device and storage device. It is developed by using electronic components. Examples of hardware are keyboard, monitor, CPU, hard disk, RAM.

  • Software

Software is a collection of program. A program is collection of instruction. An instruction is an order or command given to the computer to perform some specific task. So, software can be defined collection of instructions that instructs the computer for some specific operations. Without software, the hardware is useless. Examples of software are Windows 7, MS Windows XP, MS Office, Norton antivirus, VLC media player, Internet explorer.

  • Firmware

A Firmware is the combination of hardware and software. When a program is placed permanent memory like ROM, then the combination is called as firmware. So, it is combination of hardware (ROM) and software. Example of firmware is BIOS of computer, microcontroller chip of microwave oven, and ROM or PROM or EEPROM chips used in robots.


5. What do you mean by “Volatility”? Explain RAM and ROM with the concept and term.

  • Volatility

Volatility is the term referring to the characteristics of memory, whether the data stored in the memory will be lost after the computer is turned OFF or not. The memory is termed as volatile if the data stored in the memory is lost after the computer is turned OFF and it is termed as non-volatile, if the data stored in the memory is not lost after the computer is turned OFF.

  • RAM

RAM (Random Access Memory) is read/write memory. It is a volatile memory. It stores data and instructions required for processing, during process and after processing before providing it to the other components. It cannot store data permanently. Different types of RAM are: SRAM, DRAM.

  • ROM

ROM (Read Only Memory) is non-volatile memory. It stores programs required for operating the electronic hardware device. It stores programs permanently. Different types of ROM are: PROM, EPROM and EEPROM.

6. What is a purpose of a MODEM and where it could be used?

Purpose of a Modem and its Application:

The term MODEM is derived from the terms modulator and demodulator. Modulator is the component that translates digital signal into analog and demodulator translates analog signal to digital. So MODEM is used for translation of digital signal to analog and vice versa.

It is a network connecting device, used for connecting network mainly Internet connection by using traditional telephone system. It supports for the transmission of data over telephone or cable lines. Computer supports and requires digital data, whereas telephone lines transmit data in analog format. So, the translation is required while connecting them.

7. Describe the differences between serial and parallel interfaces.

The differences between serial and parallel interfaces are as follows:

Serial Interface Parallel Interface
It transmits data serially,1 bit at a time. It transmits data in parallel, 8 bits at a time.
It is slow. It is faster.
It is used for connecting slow speed device. It is used for connecting medium to fast speed device
It also provides electrical power supply to the connected devices. It may or may not provide power supply to the connected device as the power may not be enough.
It contains 9 pins. It contains 25 pins.
It connects devices like: keyboard, mouse.. It connects devices like: monitor, printer.

8. Describe the secondary memory in computer system with example.

Secondary Memory is the additional memory of the computer. It is also called as auxiliary memory or storage device of the computer. It is used for storing large amount of data for longer period of time. It has features like:

  • It can be magnetic, optical or flash memory.
  • It is used for permanent storage.
  • It is also used for transferring data from one computer to another.
  • It is usually cheaper.
  • Slower for read/write operation.
  •  It is used in larger storage capacity.
  • It is not directly accessible to CPU.
  •  It requires primary memory for its operations.
  • Example: Hard disk, DVD, CD, Pen drive, memory chip.

 

9.  Explain impact and non-impact printers.

Impact Printers

In impact printer, printing is done by physically touching the printing material.

Different features of impact printer are:

  • It uses mechanical method for printing.
  • It use ink ribbon for printing.
  • It is rarely used at present.
  • It is cheaper.
  • It can print multiple copies at a same time by using carbon paper.
  • It is noisy.
  • It is slow for printing.
  •  It has low printing quality.
  • It is not appropriate for printing graphics.
  • It is usually single-coloured.
  • Example: Dot matrix printer, Daisy wheel printer, Line printer.

Non-Impact Printers

Non-impact printer is a type of printer in which printing is done by spraying liquid or powder ink without touching the printing material. Different features of non-impact printer are:

  • It uses either electrostatic or electromagnetic mechanism for  printing.
  • It is commonly used at present.
  • It produces low noise.
  • It is faster for printing.
  •  It has better printing quality.
  • It is appropriate for printing graphics.
  • It can be single or multiple colored.
  • It is expensive.
  • It cannot print multiple copies at a same time.
  • It uses either liquid or powder ink for printing.
  • Example: Inkjet printer, Laser printer.

10. Describe computer virus and method of protection from virus.

Computer Virus

Computer virus is a malicious program, that disrupts the operation of 1 the computer, makes unwanted changes, modification or even deletion of data and files. It can degrade the performance of the computer. A virus can only spread from one computer to another when its host is taken to the target computer as a user sent it over a network or the internet, or carried it on a removable medium such as a floppy disk, CD, DVD, or USB drive.

The term computer virus is sometimes used to include all types of malware. Malware includes computer viruses, worms, Trojan horses, spyware, dishonest adware, crime-ware, and other malicious and unwanted software.

A computer can be protected from virus using latest updates and antivirus tools, stay informed about recent threats, and follow a few basic rules to surf the Internet, download files, and open attachments. Antivirus software periodically checks the computer system for the best-known types of viruses. It helps to protect a computer against being infected by a virus. It is used to detect and remove viruses from a computer. Having an antivirus program is essential to keep a computer running efficiently. For its effective use it needs to be updated periodically. Some of the commonly used antivirus software’s are AVG, NOD 32, Norton Antivirus and Kaspersky.

 

11. What is cache memory? How it helps to improve the performance of computer?

Cache Memory

Cache memory is a high speed memory present in between RAM and CPU. It is used for storing temporary data and instructions which are frequently required by CPU for processing.

Cache memory improves the performance of the computer by balancing the difference in working speed of RAM and CPU as CPU is much faster than RAM. When CPU requires any data, it first searches data in the cache and use from cache. Since cache memory contains frequently required data and instructions, most of the data required by CPU are available in cache. RAM is accessed only when required data is not available in the cache memory.

The performance of the computer is also increased as cache memory is normally dedicated exclusively for CPU usage while RAM is used by the Operating System and all active applications as well as by the CPU.

Cache memory is actually integrated in the CPU. This means that the CPU can directly access this memory.


Long Questions Answers

1. Define memory. Explain the types of memory in detail.

Memory is a hardware component that is capable of storing data, instruction, programs in the computer. It can store data temporarily during processing or permanently for future references. The main types of memories in a computer are: primary memory, secondary memory.

There are two types of Memories:

  • Primary memory or main memory
  • Secondary memory or auxiliary memory

 

Primary Memory

It is the main memory of the computer. It is used for storing data and instructions during processing. It is the only memory which is directly accessible to the CPU. It is usually expensive, faster for read/write operation and used in small storage capacity. Example: RAM, ROM, Cache Memory

  1. RAM (Random Access Memory) is read/write memory. It is a volatile memory. It stores data and instructions required for processing, during process and after processing before providing it to the other components. RAM are of two types: SRAM and DRAM.
    1. SRAM (Static Random Access Memory) stores data till the computer is ON state. It is faster for read/write operation than DRAM but expensive in cost. It is normally available in smaller storage capacity. It is rarely used at present.
    2. In DRAM (Dynamic Random Access Memory), the stored data will be lost after a few milliseconds even if the computer is in ON state. Refreshing circuit is required to prevent data loss. It is slower for read/write operation but cheaper in cost. It is normally available in larger storage capacity. It is commonly used at present.
  2. ROM (Read Only Memory) is non-volatile memory. It stores programs required for operating the electronic hardware device, Different types of ROM are: PROM, EPROM and EEPROM.
    1. PROM (Programmable Read Only Memory) is a blank ROM in which programs can be stored once. After storing programs in PROM, it is converted to ROM. It cannot be erased or updated.
    2. EPROM (Erasable Programmable Read Only Memory) can be erased and used multiple times. It can be erased by exposure to the UV rays. While erasing EPROM, it will be erased completely, bit by bit erasing is not possible.
    3. EEPROM (Electrically Erasable Programmable Read Only Memory) can be erased by using electrical current through the electronic circuit. Bit by bit erasing is possible.
  3.  Cache memory is a high speed memory present in between RAM and CPU. It is used for storing data and instructions which are frequently required by the CPU for processing. When the CPU requires any data, it first searches data in the cache and use from the cache. RAM is accessed only when required data is not available in the cache memory.

Secondary Memory

It is the additional memory of the computer. It is used for storing large amounts of data for a longer period of time. It is also used for transferring data from one computer to another. It is usually cheaper, slower and used in larger storage capacity. It is not directly accessible to the CPU. It requires primary memory for its operations. Example: Hard disk, DVD, CD, Pen drive. Different types of secondary memories used are: magnetic memory, optical memory and flash memory.

  1. Magnetic memory uses magnetic property for storing data. Data storing surface is coated by using magnetic oxide, the particles of the oxide stores data. It has been in use since the first generation of computers. Different magnetic memories used are: Magnetic drum, magnetic tape, magnetic disk.
    1. Magnetic tape uses thin plastic ribbon to store data. It is a sequential access memory. It is appropriate for storing audio, video, and backup. It is a rewritable, reliable memory. It has the storage capacity of up to a few GB. It requires a magnetic tape drive for its operation.
    2. Magnetic disks use circular disks made of metal or plastic. Different magnetic disk memories used are: Floppy disk, Hard disk.
  2. Floppy disks use a single plastic disk. It has the storage capacity of 1.2 MB and 1.44 MB. It is a removable disk, mainly used for transferring data from one computer to another. It requires a floppy drive for its operation.
    1. Hard disks use multiple metallic disks called platters. It has a storage capacity of up to a few TB. It is reliable, faster and has large storage capacity. So, it is used as the main storage device of the computer.
  3. Optical memory uses a laser beam for its operation. It is developed in the fourth generation of computers. It requires an optical drive for its operation. It is mainly used for storing backup, audio and video. Different optical memories used are: CD, DVD and BD (Bluray Disk).
    1. CD (Compact Disk) has a storage capacity of 700 MB. It is a circular plastic disk. Single side of the disk is used for storing data. Different types of CD are: CD-R, CD-ROM and CD-RW. CD-R (CD-Recordable) is a blank CD in which data can be [15) stored once, after storing data in CD-R, it is converted to CD ROM. A CD-ROM (CD-Read Only Memory) cannot be erased or modified. CD-RW (CD-Rewritable) can be erased and used multiple times.
    2. DVD (Digital Versatile/Video Disk) has the storage capacity of 4.7 GB to 17 GB. It is the popular storage device for storing audio and video at present. It can be single or dual sided and single or dual layered. It requires a DVD drive for its operation.
    3. BD (Bluray Disk) has the storage capacity of 25 GB to 50 GB. It is mainly used for storing HD (High definition) audio and video.
  4.  Flash memory is the semiconductor memory. It is also developed in the fourth generation of computers. Different flash memories used are: Pen drive, memory chip.
    1. Pen drive is a USB disk used as a data transferring device. It is connected to the USB port. It has a storage capacity of up to a few GB.
    2. Memory chip is the main storage device of present mobile computing devices. It has the storage capacity of up to a few GB.

3. What is CPU? Explain the major units of CPU.

The CPU (Central Processing Unit) is like the brain of a computer. Its primary function is to organize and execute instructions. CPU performs operations on data from main memory and returns the results of processing to main memory. The CPU of a microcomputer is called a microprocessor.

The functions of the CPU are:

  • To carry out processing.
  • To give commands to all parts of the computer system.
  • To control the sequence of operations.
  • To control the storage of data or instructions.

Major units of CPU are:

  • Arithmetic and Logic Unit (ALU)
  • Control Unit (CU)
  • Set of registers

Arithmetic and Logical Unit (ALU)

The function of an ALU is to perform arithmetic and logical operations. Arithmetic operations include addition, subtraction, multiplication and division. Logical operations include AND, OR, NOT operations. Arithmetic operations are used for calculations whereas logical operations are used for making comparisons and provide the capability of decision making.

Control Unit (CU)

Control Unit responsible for controlling all the components of the computer. It use control signal for controlling. It instructs the components of a computer system how to carry out a program’s instructions. It also directs the movement of electronic signals between different components of the computer.

Set of Registers

A register is a temporary memory location present inside a CPU reserved for a specific purpose. It is used for storing data and instructions during processing. CPU contains multiple registers, some of them are: Memory address register (MAR), Instruction register (IR), Accumulator register (AR).


4. What is computer software? Explain different types of software with examples.

Computer Software is a collection of programs that instructs the computer to perform some specific operation. A program is a collection of instructions. An instruction is an order or command given to the computer to perform some specific task. So, software can be defined as a collection of instructions that instructs the computer for some specific operations.

Different types of software are:

  • System software
  • Application software
  • Utility software

System software is hardware oriented software. It manages the hardware devices and creates the environment to use application software. It is the basic software required to make the hardware operate able. It is provided by the hardware developer along with the hardware. Example: Windows OS, compiler, driver of printer. Different types of system software used are:

  • Operating system is a master program that manages the hardware and software resources of the computer and makes the computer ready to use. It manages process, memory, input/output, file, data and security. Example: Windows, Linux, UNIX.
  • Language translator translates programs developed in either assembly or high level language into machine language and vice-versa. It translates source code into object code before the program is executed on the computer. Different language translators used are: assembler, compiler and interpreter.
  • Device driver is system software required to operate a particular hardware. It is provided by the hardware developer along with the hardware. Example: driver of printer, graphics, sound.

Application software is user oriented software. It is used to solve the problem of the user and make the user’s task easier. It requires system software for its operation. It is not provided by the hardware developer, the user needs to add as per need. Example: MS Office package and Banking software.

Different types of application software are:

  • Tailored software is software developed according to the needs of a particular user or organization. It contains limited features required by the user. Example: software used for billing in departmental stores, inventory management software.
  • Packaged software is ready-made software, developed with the target of a large number of users. It usually contains a large number of features. Example: MS Office package, tally, adobe Photoshop.

Utility software is the additional software used for supporting the system software for its operation. It makes the user’s task easier and effective. Example: antivirus, compression software, disk management software.


5. Define the term computer peripheral. Discuss about different types of printers with their merits and demerits.

Computer peripherals are the external or internal devices that are connected to the computer. It includes external devices like keyboard, monitor, speaker and internal devices like DVD-ROM, MODEM. Different types of printers are:

  • Impact printer
  • Non-impact printer

 Impact printer

In this type of printer, printing is done by physically touching the printing material. It uses a mechanical method for printing. It uses ink ribbon for printing. It is rarely used at present. Example: Dot matrix printer, Daisy wheel printer, Line printer.

Merits of impact printer:

  • It is cheaper.
  • It can print multiple copies at the same time by using carbon paper.

Demerits of impact printer:

  • It is noisy.
  • It is slow for printing.
  • It has low printing quality.
  • It is not appropriate for printing graphics.
  • It is usually single colored.

Non-Impact printer

In this type of printer, printing is done by spraying liquid or powder ink without touching the printing material. It uses either electrostatic or electromagnetic mechanisms for printing. It is commonly used at present. Example: Inkjet printer, Laser printer.

Merits of impact printer:

  • It produces low noise.
  • It is faster for printing.
  • It has better printing quality.
  • It is appropriate for printing graphics.
  • It can be single or multiple colored.

Demerits of impact printer:

  • It is expensive.
  • It cannot print multiple copies at the same time.

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