Computer System Overview

Chapter 1

Computer System Overview

A. Multiple Choice Questions

1. Which of the following components is the main memory of computer

(a) CD (b) DVD

2. Which component of a computer connects the processor to the other hardware?

(a) System Bus (b) CPU

3. Which of the following in referred to the brain of computer?

(a) Processor (b) RAM

4. What is the name of programs that control the computer system?

(a) Hardware (b) Keyboard

5. The physical components of a computer are called?

(a) Software (b) Hardware

6. Which of the following is the common measurement of unit of computer memory?

(a) IQ (b) Byte

7. What is the name of the component that used to both read and writes data?

(a) ROM (b) RAM

8. The CPU is also known as:

(a) The brain (b) The Processor

9. Which smaller unit of the CPU directs and coordinates all activities within it and determines the sequence in which instructions are executed, sending instructions sequence to other smaller unit.

(a) CU (b) ALU

10. Which smaller unit of the CPU performs all arithmetic and logic functions in a computer?

(a) CU (b) ALU

11. Component of CPU which is responsible for comparing the contents of two pieces of data is

(a) ALU (b) CU

12. In a computer, CU stands for:

(a) Control Unit (b) Cache unit

13. Arithmetic and logic unit along with control unit of a computer, combined into a single unit, is known as

(a) Central Processing Unit (b) Memory Unit

14. Word Processor and Desktop Publishing program are the examples of

(a) Hardware (b) Software

15. Operating System is an example of

(a) Application Software (b) System Software

16. A disk fragmentor is an example of

(a) Application Software (b) System Software

17. Flash memory and Blu-Ray disk are the example of

(a) Hardware (b) Software

18. Flash memory is a type of _____ memory

(a) Primary (b) RAM

19. Which of the following memory types will store the data or information permanently?

(a) RAM (b) Cache

20. Which of the following memory types cannot store the data or information permanently?

(a) RAM (b) Pen Drive

B. Fill in the blanks.

1. _Computer organisation__ refers to the logical structure of a computer describing their interconnections and dependency.

2. RAM and ROOM are the types of internal/primary/main memory.

3. The Arithmetic and Logic Unit (ALU) is responsible for carrying out arithmetic and logic operations.

4. The Control Unit (CU) of the CPU controls or supervises the processing taking places.

5. The small memory providing units inside the CPU are called the registers.

6. The cache memory is a special high speed memory storing the most recently accessed data.

7. The power unit of a mobile system is called battery.

8. The set of programs necessary to carry out operations/task pertaining to a specific application, are called application software.

9. Software that controls and manages internal computer operations is called system software.

10. Utility programs are a type of application software.

11. Antivirus software is a type of application software/utility software.

12. Windows OS is a type of system software.

C. State True or False.

1. A computer system consists of both hardware and software. True

2. Hardware is a set of instructions called programs that the computer uses to carry out tasks while software are all the parts of the computer you can see and touch, also known as peripherals. False

3. The two smaller units of the Processor are CU and ALU. True

4. Main memory holds data and instruction being processed by the computer and is directly accessible by the CPU. True

5. A mobile system also contains CPU. True

6. A mobile system has its own little power unit. True

7. A cache memory is a type of RAM. True

8. Language processors are a type of application software. False

9. Customized software is a type of system software. False

D. Answer the following questions.

Q1. Briefly explain the basic architecture of a computer.

Ans. A computer system comprises of five basic components:

1. Input Unit — An input unit takes the input and converts it into binary form so that it can be understood by the computer. For example, keyboard, mouse etc.

2. Output Unit — It converts the output in binary form to human readable form. For example, monitor, speakers etc.

3. Central Processing Unit (CPU) — It is responsible for processing the data and instructions. It consists of two parts:

(i) Arithmetic and Logic Unit (ALU) — It performs all the four arithmetic operations (addition, subtraction, multiplication and division) and some logical operations (less than, greater than, less than equal to, greater than equal to, equal to, not equal to).

(i)

(ii) Control Unit (CU) — It acts as a supervisor by controlling and guiding the operation taking place.

4. Primary Memory — It is the internal volatile memory where data and instructions are stored during processing. It is of two types: Random Access Memory (RAM) and Read Only Memory (ROM).

5. Secondary Storage Unit — It refers to the external storage devices which provide permanent memory to the computer system. For example, hard disk, compact disk, flash drive etc.

Q2. What do you understand by input unit? What is its significance ? What does computer input consist of?

Ans. An input unit takes the input and converts it into binary form so that it can be understood by the computer.

Since a computer operates on electricity, it can understand only the language of electricity i.e., either ON or OFF or High/Low voltage or the binary language that uses just two symbols: 1 for ON and 0 for OFF. It cannot understand the data and instructions if they are not in binary language. Thus, input unit takes data and instructions from the user and converts them into binary form so that the computer can understand them.

Different input devices take input in different forms and pass them in digital form to CPU for processing. Computer inputs may consist of:

1. letters, digits, commands from the keyboard.

2. movement of pointer using a mouse or pointing device.

3. sound input from a microphone.

Q3. What is the function of CPU in a computer system? What are its subunits?

Ans. The CPU or the Central Processing Unit is the main control centre and processing unit. It is also called brain of the computer as it guides, directs, controls and governs the performance of a computer.

The CPU has three sub-components which are as follows:

Arithmetic and Logic Unit (ALU) — It is responsible for carrying out the arithmetic instructions (add, subtract, multiply, divide) and making logic decisions (greater than, less than, equal to).

Control Unit — It is responsible for controlling and supervising the processing.

Registers — The CPU uses these small units of data holding places to temporarily hold some important processing-information during the time the processing is taking place.

Q4. What functions are performed by the control unit? Can we call it the control centre of computer system? Why?

Ans. Control Unit is responsible for controlling and supervising the processing. It performs the following functions:

It controls and guides the interpretation, flow and manipulation of all data and information.

It sends control signals until the required operations are done properly by ALU and memory.

It fetches the program instructions from the memory unit one by one. The instructions are decoded and executed one after the other.

After an instruction is executed, it sends a signal to memory to send the next instruction in sequence to CU.

It controls the flow of data from input devices to memory and from memory to output devices.

Yes, we can call control unit the control centre of computer system because it acts as a supervisor by controlling and guiding all the other components of the computer system as well as the operations taking place.

Q5. What functions are performed by the ALU? Is it an independent unit? If not, which unit does ALU work in coordination with?

Ans. Arithmetic and Logic unit is responsible for carrying out the arithmetic instructions (add, subtract, multiply, divide) and making logic decisions (greater than, less than, equal to).

No, it is not an independent unit. It is a part of CPU. It works in coordination with the commands given by the Control Unit.

Q6. Distinguish between CPU and ALU.

CPU	ALU
CPU refers to Central Processing Unit.	ALU refers to Arithmetic and Logic unit.
CPU is one of the main components of a computer system.	ALU is a sub-unit of the CPU.
CPU guides, directs, controls and governs the performance of a computer.	ALU carries out arithmetic and logic operations on the operands in computer instructions.

Q7. What is the function of output unit in a computer system? Give examples of some output devices.

Ans. Output Unit converts the output in binary form to human readable form. The output coming from the CPU is in the form of binary signals which needs conversion in some human readable form i.e,, characters, graphical or audio visual form. This function of conversion is performed by output units.

Examples of some output devices are monitor, speaker, printers, plotters etc.

Q8. What role does memory play in the functioning of computer system?

Ans. The memory of a computer is more like a predefined working place, where it temporarily keeps information and data to facilitate its performance. When the task is performed, it clears its memory and memory space is then available for the next task to be performed.

There are two types of main memory:

1. Random Access Memory

2. Read Only Memory

Since computer's main memory is temporary, secondary memory space, such as hard disk, CDs, pen drive etc., is needed to store data and information permanently for later use.

Q9. Define the following.

(a) byte (b) kilobyte (c) gigabyte (d) terabyte

Byte: A bit is an elementary unit of the memory. Eight bits together form a byte.

Kilobyte: A kilobyte is equal to 210 bytes i.e., 1024 bytes.

Megabyte: A megabyte is equal to 210 kilobytes i.e., 1024 kilobytes.

Gigabyte: A gigabyte is equal to 210 megabytes i.e., 1024 megabytes.

Terabyte: A terabyte is equal to 210 gigabytes i.e., 1024 gigabytes.

Q10. What is the meaning of the term volatile primary memory? What can be done to overcome the problems of volatility?

Ans. Volatile primary memory means that when the power goes off, the contents of the primary memory get erased.

Since computer's primary memory is volatile or temporary, secondary memory space is used to store data and information permanently for later use. Secondary storage media are the hard disk, CD-RWs, pen drive etc.

Q11. Distinguish between internal and external memory.

Ans.

Internal memory	External memory
Internal memory is also known as primary storage or main memory.	External memory is also known as secondary storage.
It is volatile in nature in case of RAM but ROM is non-volatile.	It is non-volatile in nature.
It is used to store data temporarily (in case of RAM).	It is used to store data permanently.
Internal memory is a working memory.	External memory is not a working memory.
Examples are RAM and ROM.	Examples are hard disk, CD, DVD, flash drive etc.

Q12. What is the role of memory in a computer functioning? What types of memory does the computer work with?

The computer works with two types of main memory:

1. Random Access Memory

2. Read Only Memory

Since the main memory is volatile, the computer also uses secondary memory to store data permanently.

Q13. What are RAM and ROM? How are they alike? How are they different? What are EEPROM, PROM and EPROM?

Ans. RAM refers to Random Access Memory where both read and write operations can take place. But the RAM is a volatile memory and its contents are lost when power is turned off.

ROM refers to Read Only Memory where only read operation can take place. It does not have a write capability. ROM is a non-volatile memory.

RAM and ROM are the main memory of a computer and both of them are required for the smooth functioning of a computer system.

The RAM provides memory for reading as well writing and its contents can be modified as and when required. ROM, on the other hand, stores some instructions which are permanent. ROM cannot be written onto. One can only read instructions from ROM.

EEPROM refers to electrically erasable programmable ROM. In EEPROM, the EPROM is erased electrically which is faster. Also, with EEPROM, selective bytes can be erased unlike UV-EPROM which erases fully.

PROM refers to programmable ROM. It is a user-programmable memory in which information is burnt using special equipment called a ROM burner. It can be programmed only once.

EPROM refers to erasable programmable ROM. In EPROM, one can program the memory chip through various mechanisms (e.g., UV radiation) and erase it as many times as needed. The UV-EPROM can take up to 20 minutes for erasing EPROM contents.

Q14. What is cache memory? How is it useful?

Ans. The cache memory is a high speed memory available inside CPU in order to speed up access to data and instructions stored in RAM memory. Whenever some data is required, the CPU first looks in the cache, if it is there or not. If the data is found in cache, CPU does not access memory and hence the process becomes very fast.

Memory caching is effective because most programs access the same data or instructions over and over. By keeping as much of this information as possible in cache memory (SRAM), the computer avoids accessing the slower main memory (DRAM). Hence, cache memory is useful for improving the performance of the computer.

Q15. What are major functional components of a mobile system?

Ans. The major functional components of a mobile system are as follows:

1. Mobile Processor (Mobile CPU) — This is the brain of a smartphone. It has two sub-processor types:

(i) Communications Processing Unit — responsible for making and receiving phone calls.

(ii) Applications Processing Unit (APU) — responsible for governing, controlling all types of operations taking place on a mobile system by running various apps.

2. Display Subsystem — responsible for providing display facilities, touch sensitive interface and touch sensitive keyboards.

3. Camera Subsystem — designed to deliver a tightly bound image processing package.

4. Mobile System Memory — consists of RAM (work memory) and ROM (mobile's internal storage).

5. Storage — external storage of a mobile system.

6. Power Management Subsystem (Battery) — responsible for providing power to a mobile system.

Q16 . Draw a block diagram depicting organization of a mobile system.

Ans. Block diagram depicting mobile system organization is shown below:

Q17. What is the role of power management unit in a mobile system?

Ans. The Power Management Subsystem is responsible for providing power to a mobile system. The mobile systems work on limited power provided through an attached battery unit. This subsystem has a battery management system that works with a battery charger and a battery unit, and provides power to the mobile system in required form.

Q18. What does the communication processor do?

Ans. Communication processor of a mobile system is responsible for making and receiving phone calls on a mobile handset. It has a digital signal processor that helps it work with RF Transceiver and the Audio subsystem. Radio Signal Management Unit is responsible for connecting SIM to the base stations through radio signals.

Q19. What is the role of application processing unit in a mobile system?

Ans. Applications Processing Unit (APU) is responsible for governing and controlling all types of operations taking place on a mobile system by running various types of mobile applications (apps).

Q20. How does display subsystem of a mobile system work?

Ans. Display subsystem is responsible for providing display facilities, touch sensitive interface and touch sensitive keyboards.

Q21. What are different categories of software? Give examples.

Ans. There are broadly two categories of software:

1. System Software — This type of software controls internal computer operations. The system software can further be classified in two categories:

2. Operating System — An operating system is a program which acts as an interface between a user and the hardware. For example, Microsoft Windows 10, Linux OS.

3. Language Processor — This program is responsible for converting an HLL code (High Level Language code) into machine understandable code. For example, interpreter and compiler.

4. Application Software — An application software is the set of programs necessary to carry out operations for a specified application. For example, Microsoft Word, Adobe Photoshop, etc.

Q22. What is system software? What role does it play in the functioning of the computer?

Ans. The software that controls internal computer operations such as reading data from input devices, transmitting processed information to the output devices, checking system components, converting data/instructions to computer understandable form etc., is called System Software.

The system software can further be classified into two categories:

1. Operating System — It is a program which acts as an interface between a user and the hardware. For example, Microsoft Windows 10.

2. Language Processor — It is a special type of a computer software that can translate the source code into an object code or machine code. For example, interpreter and compiler.

Q23. Discuss the role of utility software in the context of computer performance.

Ans. Utilities are those application programs that assist the computer by performing housekeeping functions like backing up disk or scanning / cleaning viruses or arranging information etc.

Utilities bridge the gaps by helping to solve the problems and maximize our computer's potential. Some important utilities are as follows:

1. Text Editor — This utility program is used for creating, editing text files.

2. Backup Utility — This utility program facilitates the backing-up of disk so that in case of any damage or data-loss, this backed up data may be used.

3. Compression Utility — This utility program facilitates compression of files. Large files can be compressed so that they take less storage area.

4. Disk Defragmentor — This program speeds up disk access by rearranging the files and free space on our computer, so that files are stored in contiguous units and free space is consolidated in one contiguous block.

5. Antivirus Software — This utility program ensures virus-free work environment. It scans our disk for viruses and removes them, if any virus is found. Moreover, some antivirus software remains present in memory all the time so that they can detect the viruses and counterattack them.

Q24. What is the importance of an OS?

Ans. An Operating System is a program which acts as an interface between a user and the hardware. For example, Microsoft Windows 10, Linux etc.

The primary goal of an operating system is to make the computer system convenient to use and secondary goal is to use computer hardware in an efficient manner. It performs the following functions:

1. It controls all other components of the computer system.

2. It coordinates the use of the hardware among the various application programs for the various users.

3. It manages the CPU time.

4. It manages the main memory of the computer.

5. It executes all the programs.

Q25. How are software libraries useful? Name some software libraries of Python.

Ans. Software libraries provide pre-written and tested code for a specific set of functions or features that can be included in a software program, saving programmers time and effort. By utilizing existing libraries, programmers can avoid having to write complex code from scratch and can benefit from the experience and knowledge of other developers who have contributed to the library. This results in more efficient coding, faster development, and more reliable software.

Some software libraries of Python are as follows:

1. NumPy (Numerical Python)

2. SciPy (Scientific Python)

3. Panda Library

Q26. How is system software different from application software?

Ans.

System Software	Application Software
It is designed to control the operations of a computer system.	It is designed to carry out specific tasks such as creating documents etc.
These programs help in the running of other software.	These programs allow a computer to perform useful tasks beyond the running of the system itself.
For example - Windows 10	For example - MS Word

Q27. What is the utility of these software?

(i) disk defragmenter software (ii) backup software

Answer

Utility software:

A file is fragmented when it becomes too large for our computer to store in a single location on a disk. When this happens, our computer splits the file up and stores it in pieces. We can use fragmented files, but it takes our computer longer to access them.

Disk Defragmenter utility program speeds up disk access by rearranging the files and free space on our computer, so that files are stored in contiguous units and free space is consolidated in one contiguous block.

Backup software:

Backup utility program facilitates the backing-up of disk. Back-up means duplicating the disk information so that in case of any damage or data-loss, this backed up data may be used.

Q28. To run your computer system, what types of software are necessary ? What role does each type play in computer's functioning?

Ans. To run our computer system, the following two types of software are necessary:

1. System Software — This type of software controls internal computer operations. The system software can further be classified in two categories:

(i) Operating System — An operating system is a program which acts as an interface between a user and the hardware. For example, Microsoft Windows 10, Linux OS.

(ii) Language Processor — This program is responsible for converting an HLL code (High Level Language code) into machine understandable code. For example, interpreter and compiler.

2. Application Software — An application software is the set of programs necessary to carry out operations for a specified application. For example, Microsoft Word, Adobe Photoshop etc.

Q29. What is the function of memory? What are its measuring units?

Ans. The memory temporarily holds the data and information during processing. The smallest unit of memory is byte (8 bits). A byte can store one character in binary for. Other measuring units are kilobyte (KB) equal to 1024 bytes, Megabyte (MB0 equal to 1024 Kilobyte, Gigabyte (GB) equal to 1024 Megabyte and Terabyte equal to 1024 Gigabyte.

Q30. Why is primary memory termed as ‘destructive write’ memory but ‘non-destructive read’ memory?

Ans. When a memory location is read from in the primary memory, the contents of the memory word remain the same; they are not altered. Therefore, a primary memory is termed as ‘non-destructive read’ memory since the read operation does not destruct the contents of a memory word. When write operation takes place, the previous contents of the memory word are overwritten. Thus, the primary memory is termed as ‘destructive write’ memory as the write operation destructs the contents of a memory word.

Q31. What is the difference between RAM and ROM?

Ans. RAM refers to random access memory where both read and write operations can take place. But the RAM is a volatile memory; its contents are lost when power is turned off. ROM refers to read only memory where only read operation can take place. The ROM is a non-volatile memory. Both RAM and ROM are parts of the primary memory.

32. What is Cache memory? Why is it considered crucial for a microprocessor’s performance?

Ans. Cache memory is a special high-speed memory that stores most recently used data in order to speed up the process of instruction execution. a cache can speed up data retrieval because recently used data is likely to be used again by the computer.

Q33. What is the difference between an interpreter and compiler?

Ans. An interpreter converts an HLL program into machine language line by line and simultaneously executes the converted line. Also, an interpreter must always be present in the memory along with the program for its execution. If an error occurs in a line, the line is displayed and interpreter does not proceed unless the error is rectified.

A compiler converts HLL program in machine language in one go. If there are errors in the program, It gives the error list along with the line numbers. Once the errors are removed, error-free object code is made available and after this compiler is no more needed in the memory.

Q34. What is application software? Why it is required?

Ans. Application software is a software that pertains to one application. Application software is required because system software cannot carry out the routine jobs performed by the user which application software can easily do.

Q35. What is system software? What role does it play in the functioning of the computer?

Ans. System software is the software that controls internal computer operations such as reading data from input devices, transmitting processed information to the output devices, checking system components, converting data/instructions to computer understandable from.

Q36. Discuss the role of utility software in the context of computer performance.

Ans. Some utility software are used to remove out-dated files, compress the large files, defragment the disks and provide security against virus threats. Hence, enhance the performance of the computer.

Q37. How does the computer understand a program written in high level language?

Ans. The program written in high level language is first converted/translated into machine language by language processor, which is then handed over to computer. Thus, the computer is able to understand the programs written in high level language.

Q38. What is the need for secondary memory?

Ans. The primary memory holds the data and instructions permanently on RAM. To store data permanently the secondary memory is required.

Q39. What do you understand by input unit? What is its significance? What does computer input consist of?

Ans. Computer input unit is formed by the input devices attached to the computer. These units are important to take input and convert it into computer understandable form (binary form which is sent to the CPU for processing. Computer input consists of data on which the action to be performed and the instructions, according which the action to be taken.

Q40. What is the function of CPU in a computer system? What are its subunits?

Ans. The CPU (Central Processing Unit) is the main control centre and processing unit. It controls, directs and governs the performance of a computer. The CPU has the following subunits:

(a) Arithmetic Logic Unit (ALU) (b) Control Unit (CU) (c) Registers

Q41. What functions are performed by the control unit? Can we call it the control centre of computer system? Why?

Ans. The control unit controls and guides the interpretation, flow and manipulation of all the data and information. It sends control signals to complete the operations. It also receives the program instructions from memory and executes them. It can be called control centre of computer because it controls the flow of instructions and other sub units to get the operations done.

Q42. What functions are performed by ALU? Is it an independent unit? If not which unit does ALU work in coordination with?

Ans. ALU performs arithmetic and logical operations. No, ALU is not an independent unit. It works in coordination with CU.

Q43. Distinguish between CPU and ALU.

Ans. CPU is central processing unit that is responsible for directing, guiding and governing of the all the processes of computer. It is made up of different subunits. ALU is a subunit of the CPU that performs arithmetic and logical operations.

Q44. What is the function of output unit in a computer system? Give examples of some output devices.

Ans. The output unit is formed by the output devices attached to the computer. Some output devices are: Monitor, printer, speaker, etc.

Q45. What role does memory play in the functioning of a computer system?

Ans. Memory stores the data and instructions in the computer system. The primary memory is very important for the functioning of the computer. The secondary memory of a computer system is mainly used for storing the data and application software in the computer system.

Q46. What is the meaning of the term volatile primary memory? What can be done to overcome the problem of volatility?

Ans. The term volatile is used with the primary memory of the computer (RAM). It means temporary memory as it holds the data so long as the computer has power. When power to the computer goes off, the contents in the RAM get erased. To overcome the volatility, the data must be saved on secondary memory.

Q46. What are the major functional components of a mobile system?

Ans. These are the major functional components of a mobile system-Mobile processor, Display Subsystem, Camera Subsystem, Mobile System Memory storage, Power Management System.

Q47. What is the role of power management unit in a mobile system?

Ans. This subsystem is responsible for providing power to the mobile system. The power is provided through an attached battery unit.

Q48. What does the communication processor do?

Ans. The communication processor is responsible for making and receiving phone calls on a mobile handset. It has a digital signal processor that helps it work with RF Transceiver and the Audio subsystem.

Q49. What is the role of application processing unit in a mobile system work?

Ans. Application processing unit is responsible for governing, controlling all types of operations taking place on a mobile system by running various types of mobile applications.

Q50. How does display subsystem of a mobile system work?

Ans. Display subsystem of mobile provides display facilities, touch sensitive interface and touch sensitive keyboards.

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