Computer - Operating System

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The Operating System is a program with the following features −

• An operating system is a program that acts as an interface between the software and the computer hardware.

• It is an integrated set of specialized programs used to manage overall resources and operations of the computer.

• It is a specialized software that controls and monitors the execution of all other programs that reside in the computer, including application programs and other system software.

 

Objectives of Operating System

The objectives of the operating system are −

• To make the computer system convenient to use in an efficient manner.

• To hide the details of the hardware resources from the users.

• To provide users a convenient interface to use the computer system.

• To act as an intermediary between the hardware and its users, making it easier for the users to access and use other resources.

• To manage the resources of a computer system.

• To keep track of who is using which resource, granting resource requests, and mediating conflicting requests from different programs and users.

• To provide efficient and fair sharing of resources among users and programs.

Characteristics of Operating System

Here is a list of some of the most prominent characteristic features of Operating Systems −

• Memory Management − Keeps track of the primary memory, i.e. what part of it is in use by whom, what part is not in use, etc. and allocates the memory when a process or program requests it.

• Processor Management − Allocates the processor (CPU) to a process and deallocates the processor when it is no longer required.

• Device Management − Keeps track of all the devices. This is also called I/O controller that decides which process gets the device, when, and for how much time.

• File Management − Allocates and de-allocates the resources and decides who gets the resources.

• Security − Prevents unauthorized access to programs and data by means of passwords and other similar techniques.

• Job Accounting − Keeps track of time and resources used by various jobs and/or users.

• Control Over System Performance − Records delays between the request for a service and from the system.

• Interaction with the Operators − Interaction may take place via the console of the computer in the form of instructions. The Operating System acknowledges the same, does the corresponding action, and informs the operation by a display screen.

• Error-detecting Aids − Production of dumps, traces, error messages, and other debugging and error-detecting methods.

• Coordination Between Other Software and Users − Coordination and assignment of compilers, interpreters, assemblers, and other software to the various users of the computer systems.

Computer -Networking

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A computer network is a system in which multiple computers are connected to each other to share information and resources.

Characteristics of a Computer Network

• Share resources from one computer to another.

• Create files and store them in one computer, access those files from the other computer(s) connected over the network.

• Connect a printer, scanner, or a fax machine to one computer within the network and let other computers of the network use the machines available over the network.

Following is the list of hardware's required to set up a computer network.

• Network Cables
• Distributors
• Routers
• Internal Network Cards
• External Network Cards

Network Cables

Network cables are used to connect computers. The most commonly used cable is Category 5 cable RJ-45.

Distributors

A computer can be connected to another one via a serial port but if we need to connect many computers to produce a network, this serial connection will not work.

The solution is to use a central body to which other computers, printers, scanners, etc. can be connected and then this body will manage or distribute network traffic.

Router

A router is a type of device which acts as the central point among computers and other devices that are a part of the network. It is equipped with holes called ports. Computers and other devices are connected to a router using network cables. Now-a-days router comes in wireless modes using which computers can be connected without any physical cable.

Network Card

Network card is a necessary component of a computer without which a computer cannot be connected over a network. It is also known as the network adapter or Network Interface Card (NIC). Most branded computers have network card pre-installed. Network cards are of two types: Internal and External Network Cards.

Internal Network Cards

Motherboard has a slot for internal network card where it is to be inserted. Internal network cards are of two types in which the first type uses Peripheral Component Interconnect (PCI) connection, while the second type uses Industry Standard Architecture (ISA). Network cables are required to provide network access.

External Network Cards

External network cards are of two types: Wireless and USB based. Wireless network card needs to be inserted into the motherboard, however no network cable is required to connect to the network.

Universal Serial Bus (USB)

USB card is easy to use and connects via USB port. Computers automatically detect USB card and can install the drivers required to support the USB network card automatically.

Computer - Data and Information

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Data can be defined as a representation of facts, concepts, or instructions in a formalized manner, which should be suitable for communication, interpretation, or processing by human or electronic machine.

Data is represented with the help of characters such as alphabets (A-Z, a-z), digits (0-9) or special characters (+,-,/,*,<,>,= etc.)

What is Information?

Information is organized or classified data, which has some meaningful values for the receiver. Information is the processed data on which decisions and actions are based.

For the decision to be meaningful, the processed data must qualify for the following characteristics −

• Timely − Information should be available when required.

• Accuracy − Information should be accurate.

• Completeness − Information should be complete.

 

Data Processing Cycle

Data processing is the re-structuring or re-ordering of data by people or machine to increase their usefulness and add values for a particular purpose. Data processing consists of the following basic steps - input, processing, and output. These three steps constitute the data processing cycle.

• Input − In this step, the input data is prepared in some convenient form for processing. The form will depend on the processing machine. For example, when electronic computers are used, the input data can be recorded on any one of the several types of input medium, such as magnetic disks, tapes, and so on.

• Processing − In this step, the input data is changed to produce data in a more useful form. For example, pay-checks can be calculated from the time cards, or a summary of sales for the month can be calculated from the sales orders.

• Output − At this stage, the result of the proceeding processing step is collected. The particular form of the output data depends on the use of the data. For example, output data may be pay-checks for employees.

Computer - Number Conversion

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There are many methods or techniques which can be used to convert numbers from one base to another. In this chapter, we'll demonstrate the following −

• Decimal to Other Base System
• Other Base System to Decimal
• Other Base System to Non-Decimal
• Shortcut method - Binary to Octal
• Shortcut method - Octal to Binary
• Shortcut method - Binary to Hexadecimal
• Shortcut method - Hexadecimal to Binary

Decimal to Other Base System

Step 1 − Divide the decimal number to be converted by the value of the new base.

Step 2 − Get the remainder from Step 1 as the rightmost digit (least significant digit) of the new base number.

Step 3 − Divide the quotient of the previous divide by the new base.

Step 4 − Record the remainder from Step 3 as the next digit (to the left) of the new base number.

Repeat Steps 3 and 4, getting remainders from right to left, until the quotient becomes zero in Step 3.

The last remainder thus obtained will be the Most Significant Digit (MSD) of the new base number.

Example

Decimal Number: 29₁₀

Calculating Binary Equivalent −

Step	Operation	Result	Remainder
Step 1	29 / 2	14	1
Step 2	14 / 2	7	0
Step 3	7 / 2	3	1
Step 4	3 / 2	1	1
Step 5	1 / 2	0	1

As mentioned in Steps 2 and 4, the remainders have to be arranged in the reverse order so that the first remainder becomes the Least Significant Digit (LSD) and the last remainder becomes the Most Significant Digit (MSD).

Decimal Number : 29₁₀ = Binary Number : 11101_2.

Other Base System to Decimal System

Step 1 − Determine the column (positional) value of each digit (this depends on the position of the digit and the base of the number system).

Step 2 − Multiply the obtained column values (in Step 1) by the digits in the corresponding columns.

Step 3 − Sum the products calculated in Step 2. The total is the equivalent value in decimal.

Example

Binary Number: 11101₂

Calculating Decimal Equivalent −

Step	Binary Number	Decimal Number
Step 1	111012	((1 x 24) + (1 x 23) + (1 x 22) + (0 x 21) + (1 x 20))10
Step 2	111012	(16 + 8 + 4 + 0 + 1)10
Step 3	111012	2910

Binary Number : 11101₂ = Decimal Number : 29₁₀

Other Base System to Non-Decimal System

Step 1 − Convert the original number to a decimal number (base 10).

Step 2 − Convert the decimal number so obtained to the new base number.

Example

Octal Number : 25₈

Calculating Binary Equivalent −

Step 1 - Convert to Decimal

Step	Octal Number	Decimal Number
Step 1	258	((2 x 81) + (5 x 80))10
Step 2	258	(16 + 5)10
Step 3	258	2110

Octal Number : 25₈ = Decimal Number : 21₁₀

Step 2 - Convert Decimal to Binary

Step	Operation	Result	Remainder
Step 1	21 / 2	10	1
Step 2	10 / 2	5	0
Step 3	5 / 2	2	1
Step 4	2 / 2	1	0
Step 5	1 / 2	0	1

Decimal Number : 21₁₀ = Binary Number : 10101₂

Octal Number : 25₈ = Binary Number : 10101₂

Shortcut Method ─ Binary to Octal

Step 1 − Divide the binary digits into groups of three (starting from the right).

Step 2 − Convert each group of three binary digits to one octal digit.

Example

Binary Number : 10101₂

Calculating Octal Equivalent −

Step	Binary Number	Octal Number
Step 1	101012	010 101
Step 2	101012	28 58
Step 3	101012	258

Binary Number : 10101₂ = Octal Number : 25₈

Shortcut Method ─ Octal to Binary

Step 1 − Convert each octal digit to a 3-digit binary number (the octal digits may be treated as decimal for this conversion).

Step 2 − Combine all the resulting binary groups (of 3 digits each) into a single binary number.

Example

Octal Number : 25₈

Calculating Binary Equivalent −

Step	Octal Number	Binary Number
Step 1	258	210 510
Step 2	258	0102 1012
Step 3	258	0101012

Octal Number : 25₈ = Binary Number : 10101₂

Shortcut Method ─ Binary to Hexadecimal

Step 1 − Divide the binary digits into groups of four (starting from the right).

Step 2 − Convert each group of four binary digits to one hexadecimal symbol.

Example

Binary Number : 10101₂

Calculating hexadecimal Equivalent −

Step	Binary Number	Hexadecimal Number
Step 1	101012	0001 0101
Step 2	101012	110 510
Step 3	101012	1516

Binary Number : 10101₂ = Hexadecimal Number : 15₁₆

Shortcut Method - Hexadecimal to Binary

Step 1 − Convert each hexadecimal digit to a 4-digit binary number (the hexadecimal digits may be treated as decimal for this conversion).

Step 2 − Combine all the resulting binary groups (of 4 digits each) into a single binary number.

Example

Hexadecimal Number : 15₁₆

Calculating Binary Equivalent −

Step	Hexadecimal Number	Binary Number
Step 1	1516	110 510
Step 2	1516	00012 01012
Step 3	1516	000101012

Hexadecimal Number : 15₁₆ = Binary Number :

Computer - Number System

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When we type some letters or words, the computer translates them in numbers as computers can understand only numbers. A computer can understand the positional number system where there are only a few symbols called digits and these symbols represent different values depending on the position they occupy in the number.

The value of each digit in a number can be determined using −

• The digit

• The position of the digit in the number

• The base of the number system (where the base is defined as the total number of digits available in the number system)

Decimal Number System

The number system that we use in our day-to-day life is the decimal number system. Decimal number system has base 10 as it uses 10 digits from 0 to 9. In decimal number system, the successive positions to the left of the decimal point represent units, tens, hundreds, thousands, and so on.

Each position represents a specific power of the base (10). For example, the decimal number 1234 consists of the digit 4 in the units position, 3 in the tens position, 2 in the hundreds position, and 1 in the thousands position. Its value can be written as

(1 x 1000)+ (2 x 100)+ (3 x 10)+ (4 x l) (1 x 103)+ (2 x 102)+ (3 x 101)+ (4 x l00) 1000 + 200 + 30 + 4 1234 

As a computer programmer or an IT professional, you should understand the following number systems which are frequently used in computers.

S.No.	Number System and Description
1	Binary Number System Base 2. Digits used : 0, 1
2	Octal Number System Base 8. Digits used : 0 to 7
3	Hexa Decimal Number System Base 16. Digits used: 0 to 9, Letters used : A- F

Binary Number System

Characteristics of the binary number system are as follows −

• Uses two digits, 0 and 1

• Also called as base 2 number system

• Each position in a binary number represents a 0 power of the base (2). Example 2⁰

• Last position in a binary number represents a x power of the base (2). Example 2^x where x represents the last position - 1.

Example

Binary Number: 10101₂

Calculating Decimal Equivalent −

Step	Binary Number	Decimal Number
Step 1	101012	((1 x 24) + (0 x 23) + (1 x 22) + (0 x 21) + (1 x 20))10
Step 2	101012	(16 + 0 + 4 + 0 + 1)10
Step 3	101012	2110

Note − 10101₂ is normally written as 10101.

Octal Number System

Characteristics of the octal number system are as follows −

• Uses eight digits, 0,1,2,3,4,5,6,7

• Also called as base 8 number system

• Each position in an octal number represents a 0 power of the base (8). Example 8⁰

• Last position in an octal number represents a x power of the base (8). Example 8^x where x represents the last position - 1

Example

Octal Number: 12570₈

Calculating Decimal Equivalent −

Step	Octal Number	Decimal Number
Step 1	125708	((1 x 84) + (2 x 83) + (5 x 82) + (7 x 81) + (0 x 80))10
Step 2	125708	(4096 + 1024 + 320 + 56 + 0)10
Step 3	125708	549610

Note − 12570₈ is normally written as 12570.

Hexadecimal Number System

Characteristics of hexadecimal number system are as follows −

• Uses 10 digits and 6 letters, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F

• Letters represent the numbers starting from 10. A = 10. B = 11, C = 12, D = 13, E = 14, F = 15

• Also called as base 16 number system

• Each position in a hexadecimal number represents a 0 power of the base (16). Example, 16⁰

• Last position in a hexadecimal number represents a x power of the base (16). Example 16^x where x represents the last position - 1

Example

Hexadecimal Number: 19FDE₁₆

Calculating Decimal Equivalent −

Step	Binary Number	Decimal Number
Step 1	19FDE16	((1 x 164) + (9 x 163) + (F x 162) + (D x 161) + (E x 160))10
Step 2	19FDE16	((1 x 164) + (9 x 163) + (15 x 162) + (13 x 161) + (14 x 160))10
Step 3	19FDE16	(65536+ 36864 + 3840 + 208 + 14)10
Step 4	19FDE16	10646210

Note − 19FDE₁₆ is normally written as 19FDE.

Computer - Software

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Software is a set of programs, which is designed to perform a well-defined function. A program is a sequence of instructions written to solve a particular problem.

There are two types of software −

• System Software
• Application Software

System Software

The system software is a collection of programs designed to operate, control, and extend the processing capabilities of the computer itself. System software is generally prepared by the computer manufacturers. These software products comprise of programs written in low-level languages, which interact with the hardware at a very basic level. System software serves as the interface between the hardware and the end users.

Some examples of system software are Operating System, Compilers, Interpreter, Assemblers, etc.

Here is a list of some of the most prominent features of a system software −

• Close to the system
• Fast in speed
• Difficult to design
• Difficult to understand
• Less interactive
• Smaller in size
• Difficult to manipulate
• Generally written in low-level language

Application Software

Application software products are designed to satisfy a particular need of a particular environment. All software applications prepared in the computer lab can come under the category of Application software.

Application software may consist of a single program, such as Microsoft's notepad for writing and editing a simple text. It may also consist of a collection of programs, often called a software package, which work together to accomplish a task, such as a spreadsheet package.

Examples of Application software are the following −

• Payroll Software
• Student Record Software
• Inventory Management Software
• Income Tax Software
• Railways Reservation Software
• Microsoft Office Suite Software
• Microsoft Word
• Microsoft Excel
• Microsoft PowerPoint

 

Features of application software are as follows −

• Close to the user
• Easy to design
• More interactive
• Slow in speed
• Generally written in high-level language
• Easy to understand
• Easy to manipulate and use
• Bigger in size and requires large storage space

Computer - Hardware

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Hardware represents the physical and tangible components of a computer, i.e. the components that can be seen and touched.

Examples of Hardware are the following −

• Input devices − keyboard, mouse, etc.

• Output devices − printer, monitor, etc.

• Secondary storage devices − Hard disk, CD, DVD, etc.

• Internal components − CPU, motherboard, RAM, etc.

 

Relationship between Hardware and Software

• Hardware and software are mutually dependent on each other. Both of them must work together to make a computer produce a useful output.

• Software cannot be utilized without supporting hardware.

• Hardware without a set of programs to operate upon cannot be utilized and is useless.

• To get a particular job done on the computer, relevant software should be loaded into the hardware.

• Hardware is a one-time expense.

• Software development is very expensive and is a continuing expense.

• Different software applications can be loaded on a hardware to run different jobs.

• A software acts as an interface between the user and the hardware.

• If the hardware is the 'heart' of a computer system, then the software is its 'soul'. Both are complementary to each other.