Computer - Intranet & Internet

• Internet is a world-wide/global system of interconnected computer networks.
• Internet uses the standard Internet Protocol (TCP/IP)
• Every computer in internet is identified by a unique IP address.
• IP Address is a unique set of numbers (such as 110.22.33.114) which identifies a computer location.
• A special computer DNS (Domain Name Server) is used to give name to the IP Address so that user can locate a computer by a name.
• For example, a DNS server will resolve a name http://www.tutorialspoint.com to a particular IP address to uniquely identify the computer on which this website is hosted.
• Internet is accessible to every user all over the world.

Intranet

• Intranet is system in which multiple PCs are networked to be connected to each other.
• PCs in intranet are not available to the world outside of the intranet.
• Usually each company or organization has their own Intranet network and members/employees of that company can access the computers in their intranet.
• Each computer in Intranet is also identified by a IP Address, which is unique among the computers in that Intranet.

Similarities in Internet & Intranet

• Intranet uses the internet protocols such as TCP/IP and FTP.
• Intranet sites are accessible via web browser in similar way as websites in internet. But only members of Intranet network can access intranet hosted sites.
• In Intranet, own instant messengers can be used as similar to yahoo messenger/gtalk over the internet.

Differences in Internet & Intranet

• Internet is general to PCs all over the world where Intranet is specific to few PCs.
• Internet is wider access and provides a better access to websites to large population whereas Intranet is restricted.
• Internet is not as safe as Intranet as Intranet can be safely privatized as per the need.

Computer - Operating System

• An operating system is a program that acts as an interface between the software and the computer hardware.
• It is an integration set of specialised programs that are used to manage overall resources and operations of the computer.
• It is a specialised 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

• Making a 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 and making it easier for the users to access and use other resources.
• Manage the resources of a computer system.
• Keep track of who is using which resource, granting resource requests, according for resource using and mediating conflicting requests from different programs and users.
• The efficient and fair sharing of resources among users and programs.

Characteristics of Operating System

• Memory Management -- It keeps track of primary memory, i.e., what parts of it are in use by whom, what parts are not in use, etc. Allocates the memory when the process or program requests it.
• Processor Management -- Allocates the processor (CPU) to a process. Deallocate processor when processor is no longer required.
• Device Management -- Keeps tracks of all devices. This is also called I/O controller. Decides which process gets the device when and for how much time.
• File Management -- Allocates the resources. Deallocates the resource. Decides who gets the resources.
• Security -- By means of passwords & similar other techniques, preventing unauthorized access to programs & data.
• Job accounting -- Keeping track of time & resources used by various jobs and/or users.
• Control over system performance -- Recording delays between requests for a service & from the system.
• Interaction with the operators -- The interaction may take place via the console of the computer in the form of instructions. Operating System acknowledges the same, do the corresponding action and inform 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

What is a Computer Network?

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

Characteristics

• 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 network.

Following is the list of hardwares required to set up a computer network:

• Network Cables
• Distributors
• Router
• Internal Network Cards
• External Network Cards

Network Cables

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

Distributors

• Each and every 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 part of a network.
• A router is equipped with holes called ports.
• Computers and other devices are connected to a router using network cables.
• Nowadays, 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.
• Also known as network adapter or Network Interface Card (NIC).
• Most of 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:
• First type uses Peripheral Component Interconnect (PCI) connection.
• Second type uses Industry Standard Architecture (ISA).
• Network cables are required to provide network access.

External Network Cards

• Comes in two flavors: Wireless and USB based.
• Wireless network card needs to be inserted into the motherboard but no network cable is required to connect to network.

• USB cards are easy to use and connect via USB port.
• Computer automatically detects USB card and can install the drivers required to support the USB network card automatically.

Computer - Data

What is Data?

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 like alphabets (A-Z, a-z), digits (0-9) or special characters(+,-,/,*,<,>,=, etc.).

What is Information?

Information is organised or classified data so that it has some meaningful values to 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 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 & add values for particular purpose.
Data processing consists of basic steps input, processing and output. These three steps constitute the data processing cycle.

• Input - In this step, the input data are 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 could be recorded on any one of several types of input mediums, such as magnetic disks, tapes and so on.
• Processing - In this step, input data are changed to produce data in a more useful form. For example, pay-checks may be calculated from the time cards or a summary of sales for the month may be calculated from the sales orders.
• Output -Here, the results of the proceeding processing step are 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.

Computers - Number Conversion

There are many methods or techniques, which can be used to convert numbers from one base to another. We'll demonstrate here 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

Steps

• 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 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: 11101₂.

Other base system to Decimal System

Steps

• 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

Steps

• 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

Steps

• 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

Steps

• 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

Steps

• 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

Steps

• 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: 10101₂