DATA REPRESENTATION AND GENERATIONS OF COMPUTER

 

DATA REPRESENTATION -

 

Memory Units:

 

4 bit = 1 nibble

8 bit = 1 byte

1024 B = 1 KB (Kilo Byte)

1024 KB = 1 MB (Mega Byte)

1024 MB = 1 GB (Giga Byte)

1024 GB = 1 TB (Tera Byte)

1024 TB = 1 PB (Peta Byte)

1024 PB = 1 XB (Exa Byte)

1024 XB = 1 ZB (Zeta Byte)

1024 ZB = 1 YB (Yota Byte)

 

bit < Byte < KB < MB < GB < TB < PB < XB < ZB < YB

 

    bit (b)

    Byte (B)

 

Mbps – mega bits per sec.

MBps – mega Bytes per sec.

 

    The information you put into the computer is called Data

    Information of a computer is stored as Digital Data

    A number system defines a set of values that is used to represent Quantity

    In which number system, the modern computers are operated?

 

Binary Number System

 

    Name the most significant bit, which represent 1 and 0 for a positive number and negative number, respectively.

 

Sign Bit

 

    Which coding scheme represents data in a binary form in the computer system? ASCII, EBCDIC and Unicode are the most commonly used codes under this scheme.

 

Binary Coding Scheme

 

    EBCDIC is a 8-Bit code with 256 different representations of characters. It is mainly used in mainframe computers.

    EBCDIC stands for Extended Binary Coded Decimal Interchange Code

    In the Hexadecimal Number System each number represents a power of 16. To represent the decimal numbers, this system uses numbers from 0 to 9 and characters from A to F to represent numbers 10-15, respectively. It is commonly used as a shortcut notation for groups of four binary digits

    BCD is a method that represents the decimal digits with the help of binary digits. It takes advantage that one decimal numeral can be represented by 4-bit pattern. BCD stands for Binary Coded Decimal

    This coding system is used to represent the interval storage area of the computers. In this system, every character is represented by a combination of bits. Binary Coding System

    The Base or Radix of the decimal number system is 10

    The arithmetic operations (addition, subtraction, multiplication and division) performed on the binary numbers is called Binary Arithmetic

    What is the standard code the computer industry created to represent characters? American Standard Code for Information Interchange (ASCII)

    ASCII is a code used for standardizing the storage and transfer of information amongst various computing devices.

    It is required for representing more than 64 characters. At present, the mostly used coding systems are ASCII and EBCDIC

    Which code is also known as Reflected Code? Gray Code

    The 7-bit ASCII code is widely used for Two (0 or 1)

    In the binary language, each letter of the alphabet, each number and each special character is made up of a unique combination of Eight Bits.

 

GENERATIONS OF COMPUTER

 

    Which was the first general purpose computer, designed to handle both numeric and textual information? Universal Automatic Computer (UNIVAC) (1951)

 

First Generation (1940-1956) Vacuum Tubes:

 

    The first computers used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous, taking up entire rooms.

    The UNIVAC and ENIAC computers are examples of first-generation computing devices.

    In first generation of computer, this operating system allowed only one program to run at a time and a number of input jobs are grouped for processing. It is known as Batch Processing.

 

Second Generation (1956-1963) Transistors:

 

    Transistors replaced vacuum tubes and ushered in the second generation of computers.

 

Third Generation (1964-1971) Integrated Circuits:

 

    The development of the integrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.

 

Fourth Generation (1971-Present) Microprocessors:

 

    The microprocessor brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip.

    What in the first generation filled an entire room could now fit in the palm of the hand

    Fourth generation computers also saw the development of GUIs, the mouse and handheld devices

 

Fifth Generation (Present and Beyond) Artificial Intelligence:

 

    Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today.

    In 1981 IBM introduced its first computer for the home user, and in 1984 Apple introduced the Macintosh.

VIRUS

 

 What is Computer VIRUS ? Everything you need to know

 

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When I first read about computer virus, I was surprised to know it is not ‘virus’ – but VIRUS!

 

VIRUS is actually an acronym for Vital Information Resource Under Siege!

 

Everyone says computer technology is changing every day – true – so are viruses changing and evolving every single day; thus it only makes sense we know a little about these mischief makers.

 

To help with the MCQs, I have italicized and bold-ended the proper terms.

 

Here we go:

 

What is a VIRUS?

It is actually a program, created by people who have knowledge to write software programs. In proper terms, it is called an ‘executable program’, with bad intentions!

 

Viruses are a type of malware, i.e., it is malicious software. You’ll read about it some more later…

How does it work? (Or, how does it make out lives difficult!)

A come attached with another program, and once it is in our system and we execute our program- we run the virus too!

 

The virus replicates itself; that is multiplies when has attached itself to a computer through an infected program.

 

So, suppose we download an mp3 song from some suspicious looking website, and we do not have anti-virus software on our PC, in such a case a virus may get downloaded along with the mp3.

 

Once, the virus is in our computer, it then starts making copies of itself on our computer. So, you can imagine, once it replicates, it must need space, thus a virus uses up the hard disk space and that makes our PC/system slow and makes it hang or crash!

What other damages does it do? (-apart from crashing our PC and frustrating us?)

Depending on what the intention of the person programming the virus was, a virus can do many different types of damages, like :

 

(i) modification of data (Transformers movie anyone?)

(ii) files maybe overwritten with false information

(iii) files maybe damaged, so you can not open them anymore or work on them

(iv) it may even wipe out an entire drive!

(v) it may make your system to re-boot again and again

(vi) high threat viruses which target databases of big organizations and MNCs may even leak top security information of the companies…

 

A Virus can be programmed to do anything, so its threat can be anything; it’s a creepy virtual world out there!

Famous Viruses?

Yep, Viruses are sometimes accorded celebrity status too!

 

(i) First actual virus – Creeper (1970s), detected on ARPANET.

                                    It displayed a message on the screen, “I am the creeper, catch me if

                                    you can!”

 

(ii) First actual personal computer virus – Elk Cloner (1982), it affected Apple OS

                                                                    through a floppy and displayed a short poem!

 

(iii) First virus to hit Microsoft’s DOS – Brain (1986)

 

(iv) Most destructive virus – MYDoom (January 2004)

 

(v) Most widespread and fast spreading virus – ILOVEYOU, also known as the love letter! (2000)

Categories of Viruses?

Yes, Viruses are categorized based on what/where/how they affect.

 

(i)File Virus/Parasitic Virus: most of the viruses fall in this category. In this type the viruses come attached to a file, usually a file which is executable, i.e., it can be run.

 

(ii) Boot sector Virus: these viruses, as the name suggest, affect the boot sector. Which means it will load before the operating system. It infects through floppy disks/ hard disks drives.

 

Imagine, a virus loading before the operating system does! This can only mean trouble!

 

(iii) Macro Viruses: Macro programs consist of a set of commands which executes itself every time it is run. So, this type of virus affects a program/application/software’s macros programming feature, to infect documents.

 

(iv) Multipartite Viruses: spread and infect in multiple ways, they can effect the boot sector as well as infect documents/files. They can have multiple means of transmission and of infection.

 

 

6. What are worms, malware etc.?

 

(i) Malware – is the short for malicious software, as the standard definition goes – is any software which can disrupt normal computer operation, gather sensitive information or gain access to private system.

 

It is also sometimes referred to as badware. Malwares are essentially of two types: (1) Viruses and (2) Worms.

 

(ii) Worms: worms are like viruses in the sense that they do the same damages that viruses do, they also replicate themselves.

 

However the main difference being, it is a standalone malware – i.e., it does not need to attach itself to any host/executable file. It on its own actively transmits itself through a network and infects computers.

 

In other words for virus infection to happen, a user has to actually run the virus infected program, only then will the virus program run too. But worms spread by themselves!

 

(iii) Trojan horse: This is my favorite malware as it is named on a very interesting piece of history which involves Achilles and his heel!

 

Also known as the Trojan, it is a malicious software which run without the knowledge of the user, to gather sensitive information.

 

Its specialty is it can run undetected, or when the system is shut down. It can encrypt/decrypt files and documents and transmit them to those who want it.

 

Trojan are disguised in the form of a legitimate and desirable program, that any user would without suspicion run. User thinks that the program it is running has nothing wrong with it, whereas the Trojan is secretly doing its work!

 

Trojan can also be called a ‘Spyware’; but it is NOT a virus. Why? Simply because Trojans do not replicate like viruses do!

 

(iv) Rootkits: are programs that modify setting in the operating system to keep the malwares hidden from detection.

How can we keep viruses away?

 

By installing anti-virus softwares!

 

This is probably something every one you must have heard or seen or installed one yourself!

 

Anti-virus software protects your system by periodically scanning its files/documents/programs to check for hidden executable programs.

 

It works by searching for those which are a match to any pre-defined virus already stored in its virus definition file. When there is a match, the anti-virus tells you that your PC has been infected by ‘so-and-so’ virus, and will proceed to remove it.

 

If it finds that there exists a program which is suspicious, but the anti-virus does not know its name, then it’ll ask you to take appropriate action.

 

Every other day new viruses are programmed and unleashed, and every other day thousands of e-mails are opened, movies/songs/files/softwares etc. are downloaded and these viruses find their way into out PCs.

 

That is why it is very essential for any PC to have an updated anti-virus all the time!

 

I hope this topic was informative and enjoyable!

 

Next time you run a virus scan on your PC, take some time and read the descriptions written alongside the viruses detected; some will be malwares, some worms and some Trojans!

 

Beware!

 

But keep learning and sharing knowledge and giving enthusiastic feedbacks!

DBMS - Basics, Terms and Points to Remember

 

 DBMS - Basics, Terms and Points to Remember

 

  

 

I am going to start writing on Computer topics, starting with, what most you (the non-engineering ones), consider as a difficult topic – DBMS.

 

Only because it sounds so serious and technical doesn't actually mean it’s a tough topic to understand. Trust me, when I first read the chapter, every thing sounded Greek and Latin* to me, so, I re-read it couple of more times and I forgot what had been so difficult!

 

So, what is DBMS? It is Data Base Management System. Off course!

 

I’m sure all you know the full form, but have you really ever given a thought to the words that make up the full form – ‘cause that is where the entire secret lies in understanding the core of this chapter!

 

 

Data – is any input which has been processed. It can be in numeric, alphabetic or alphanumeric form. Try to imagine data as physical files…the kind of dusty files found in government offices.

 

This processed data (or dusty files) needs to be stored and kept somewhere, so that when we need them we can easily retrieve it.

 

But where do we keep it? How do we keep it?

 

Don’t worry; the computer experts have solved your problem by creating the ‘database’.

 

Database – is simply a ‘place’ where all the data are collected and stored in an organized manner.

 

Think of it as a collection of many steel racks, like the ones found in old government offices! All the files/data are kept according to their serial numbers/file/folder names (or any other identification style), and stored in the racks/database.

 

Management system – In government officers, there are peons who are responsible for keeping the files in the right place, bringing required files to the senior officers, putting it back again after updating the files etc., this is nothing but the system of file management in the office.

 

Similarly, in computer’s database, it’s ‘management system’ is doing the work of the peon; bring the required files, putting back in the right place, etc. but more efficiently than a peon and faster too!!

 

I really do hope some vapour-ish ideas are forming in your head about DBMS!

 

Thus, putting down all our ideas in definition form – DBMS is a software,

(i) which helps a user in creating a collection of records and information and storing them on the computer in a systematic way (database),

(ii) it also helps in organizing, sorting and retrieval of the records/information from the database, when required by the user, to help the user in decision making (management system).

DBMS MODEL

Benefits of DBMS:-

 

    Faster storage and retrieval time

    Accessing data is easy and fast

    Data integrity(credibility of the data) and security. In govt. offices, anyone can pick up any file! But DBMS requires password authorization to access important files.

    Backups and recovery are possible only in digital world, hence today physical files are becoming extinct.

 

Points to remember in DBMS

 

    In DBMS data are stored in relational model, using tables with rows and columns (remember the steel racks!).

 

    There are two types of Data Manipulation Languages (DML), Structured Query Language (SQL) and Data Definition Language (DDL).

 

    DML are computer languages also known as query language, it is used for accessing and working on the data.

 

    In other words, DML (SQL and DDL), are like the languages people use, Hindi or English, in an office to give orders to the peon!

 

    Data redundancy – which means there are no duplications of data. No multiple files of the same kind.

 

    Data dictionary – is like a normal dictionary, but containing metadata.

 

    Metadata – contains information about all the data in the DBMS.

 

    The Keys – Primary key is used to identify a particular or specific record (file). It is unique to a particular file.

 

    Foreign Key makes a connection between a component (field) in one table with a component identified by a primary key.

 

    Relational database – is the kind of database model, where there are logical connections between the various files, which are kept in tables.

 

    For example: In the given diagram, the information is stored in tables (with rows and columns), in this particular case in two relational tables.

    Every column has a Field name (employee ID, first name, last name, e-mail ID, Department ID and Department name).

    The relation between the two tables is created by the field ‘Department ID’, which connects the Employees name/ID/e-mail to a particular Department like HR or software or accounts.

 

    This is relational database, where a relation is made between items of the database.

 

    

    DBMS

 

That’s all folks.

 

I am hoping that DBMS is no more vapour-ish but solid concrete! It can not get simpler than this!

 

Keep learning and keep sharing the knowledge - that’s the best way to gain knowledge

Computer Networks

 

Computer Networks

1. Computer Network is for aiding ‘Data Communication’, i.e., sending and receiving of data between terminals situated at different places.

 

2. There are 3 types of ‘Transmission Channels’, namely, Simplex, Half Duplex and Full Duplex Channels.

 

3. A(sender) à B(receiver) : is the simplex channel, where data transmission is in one way direction. Here the receiver can not send any communication back to the sender via the same channel.

 

4. Half Duplex channel – where the transmission of data is from both ends, but at any particular time only one is happening, either incoming or outgoing transmission. The diagram bellow shows a gap in space between the sender and receiver messages, to denote the gap in time where at one time only one message (either form the sender or from the receiver) will get transmitted.

Half duplex

 

5. Full Duplex channel, is where the data gets transmitted in both directions at the same time, i.e., there is no time lag or delay in communication.

 

Full duplex

 

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Network Topology

6. There are 4 main types of ‘Network Topology’, namely, Mesh, Star, Ring and Bus Network.

 

7. Topology means the arrangement of various components of a network (such as server/hubs/nodes/links/information flow channels etc.), and depicts the structure of a network.

 

8. The following diagrammatic representation is of ‘Mesh Networking’ – the small rectangular boxes are ‘Nodes’.

 

In mesh network, each node is independent, and is used for high traffic transmission through multiple available routes. This is a fully connected network, where each node in the network to the other.

Mesh topologies

 

As you can see in the diagram, each node is connect to the other four, which is why this type of network is highly reliable for data transmission as there are more than one route for transmission.

 

Plus is a particular route fails – then the transmission can automatically switch to other available routes and the transmission will be successfully completed.

 

 

9. In ‘Star Network’, there is a ‘Cental Node’, which is also called the ‘Hub’. For your easy understanding, think of hub as a Server and the other nodes attached to it are the client nodes.

 

Star topologies

The communication between the clients takes place through the server. A client (sender) send information to the hub, the hub then transmits the information to the client (receiver) for whom the information was meant to be transmitted.

 

In this type of network, if the transmission line between the hub and a node fails, then that node will become isolated from the network.

 

And if the central node fails, then the whole network fails!

 

 

10. In ‘Ring Network’ topology, each node is connected to two other nodes only.

 The data flow is usually one way in a ring network, and hence if any line/node fails then the entire network crumbles.

Ring topologies

 

11. ‘Bus Network is the type of topology in which the nodes are connected by a single communication line. This single communication line is called a bus.

Bus network

 

The bus networks are the simplest of networks, but it has a critical drawback. It can transmit from one node at a time, because of the single line of communication.

 

12. Node is a connection point where data transmission originates or ends.

 

Network Terminals

13. Terminal is a computer network means a computer equipment, it could be anything – a computer, an ATM machine, the PNR and Train time requesting machines at railway stations.

 

14. Dumb Terminals are those terminals which cannot do any processing or storage of data. It is simply an input/output device wired into another computer. It takes the input, transmits the data to the computer (computers can process!) to which it is connected and then displays the output.

 

Examples: Like PNR status checking booth at Railway stations. They have a Cathode Ray Tube (Screen), a Keyboard, or screen with touch input and gives the output on the screen.

 

15. Intelligent Terminals is the kind of terminal which can do its own processing…which would mean it is fitted with a processor and has memory (storage) capacity and thus is actually a computer (but not the kind which looks like our PC!)

 

16. Smart Terminals have processing capacities and memory too, but lesser than intelligent terminals.

 

So the hierarchy would be (lowest to highest ) – Dumb – Smart – Intelligent Terminals.

 

 

There you go guys computer network and its absolute basics – hope this was helpful!

 

Have a good day. Keep learning and keep sharing!