Question Discussion & Solution

Spam:

• the word spam is commonly used to describe unsolicited e-mails that are sent in bulk.
• It is the use of electronic messaging systems like emails and other digital delivery systems to send unwanted bulk messaged indiscriminately.
• Spamming means posting or emailing unsolicited advertising messages to a wide audience.
• It is used by companies to market their products, sometimes they are also used for dubious purposes to scam innocent people.

A virus

• It is a program that can infect other programs by modifying them to include a possibly evolved copy of itself.
• A computer Virus is nothing but a computer program that does unwanted things with your computer resources e.g. you are working on PC and you are repeatedly receiving the annoying message.
• A computer virus passes from computer to computer like a biological virus passes from person to person
• Common types of virus: File virus, Macro virus, Trojan Horse, Worm

Worm:

• A computer worm is a type of malware that spreads copies of itself from computer to computer.
• A worm can replicate itself without any human interaction, and it does not need to attach itself to a software program in order to cause damage.

Threat:

• A computer threat can be "intentional" such as hacking or "accidental" such as malfunctioning or physical damage.
• Security threat is defined as a risk which can potentially harm computer systems and organization.

Hence, it is clear that An unsolicited e-mail message sent to many recipients at once is called Spam.

Concept:

Classes in java are the collection of objects which has some similar properties. A class in java contains fields, methods, constructors, blocks, interfaces.

Explanation:

Everything is associated with classes and objects. An object is an instance of the class which has some state and behavior.

An object class(java.lang.object) is the parent class of all the java classes.  It can be used when we do not know about the type of the object. By having the object as the super class , without knowing the type we can pass around objects using the object declaration.

The correct answer is Leeuwenhoek.

Key Points

Additional Information

• Penicillin:
  • Penicillin is one of the first and still one of the most widely used antibiotic agents, derived from the Penicillium mold.
  • In 1928 Scottish bacteriologist Alexander Fleming first observed that colonies of the bacterium Staphylococcus aureus failed to grow in those areas of a culture that had been accidentally contaminated by the green mold Penicillium notatum.
  • He isolated the mold, grew it in a fluid medium, and found that it produced a substance capable of killing many of the common bacteria that infect humans.
  • Australian pathologist Howard Florey and British biochemist Ernst Boris Chain isolated and purified penicillin in the late 1930s, and by 1941 an injectable form of the drug was available for therapeutic use.
• Microscope:
  • Microscope is an instrument that produces enlarged images of small objects, allowing the observer an exceedingly close view of minute structures at a scale convenient for examination and analysis.
  • Although optical microscopes are the subject of this article, an image may also be enlarged by many other waveforms, including acoustic, X-ray, or electron beam, and be received by direct or digital imaging or by a combination of these methods.
  • The microscope may provide a dynamic image (as with conventional optical instruments) or one that is static (as with conventional scanning electron microscopes).
• Reverse transcriptase:
  • Reverse transcriptase also called RNA-directed DNA polymerase, an enzyme encoded from the genetic material of retroviruses that catalyzes the transcription of retrovirus RNA (ribonucleic acid) into DNA (deoxyribonucleic acid).
  • This catalyzed transcription is the reverse process of normal cellular transcription of DNA into RNA, hence the names reverse transcriptase and retrovirus.
  • Reverse transcriptase is central to the infectious nature of retroviruses, several of which cause disease in humans, including human immunodeficiency virus (HIV), which causes acquired immunodeficiency syndrome (AIDS), and human T-cell lymphotropic virus I (HTLV-I), which causes leukemia.
• Bacteria:
  • Bacteria, singular bacterium, any of a group of microscopic single-celled organisms that live in enormous numbers in almost every environment on Earth, from deep-sea vents to deep below Earth’s surface to the digestive tracts of humans.
  • Bacteria lack a membrane-bound nucleus and other internal structures and are therefore ranked among the unicellular life-forms called prokaryotes.
  • Prokaryotes are the dominant living creatures on Earth, having been present for perhaps three-quarters of Earth history and having adapted to almost all available ecological habitats.
  • As a group, they display exceedingly diverse metabolic capabilities and can use almost any organic compound, and some inorganic compounds, as a food source.

The correct answer is Amlanand Ghosh.

Key Points

• Prof Amlanand Ghosh excavated the Kalibangan site in 1952.
• The Kalibangan civilization is supposed to older than 4000 BC.
• This Rajasthan civilization was the first metropolis state in India.
• Kalibangan lies along with the left Bank of the dried-up bed of river Ghaggar.
• The site contains both pre-Harappan and Harappan remains, and therein can be seen the transition between the two cultures.
• Although the pre-Harappan culture worked copper and produced pottery, it had no writing system, and its ruins lack the orderly layout and use of baked brick that is found in the later Harappan sites.
• The Harappan remains include a cemetery and a fortified citadel. 

Additional Information

• Ratna Chandra Agrawal: 
  • Bhinmal Civilization was first founded by Ratna Chandra Agrawal in 1953-54 AD.
  • Bhinmal civilization is founded in the Jalore District of Rajasthan.
• Ratan Lal Mishra: 
  • Ganeshwar civilization was first founded in 1977 by historian Ratan Lal Mishra.
  • This Ganeshwar civilization is more than 4000 years old and the estimated time period was 2500 – 2000 BC.

The correct answer is Single-User Operating System.

Important Points

• Single-User Operating System
  • Performs a single task for Single-user.
  • This operating system is designed to manage the computer so that one user can effectively do one thing at a time.
  • Examples include Microsoft Windows.

Additional Information

• The different types of Operating System:
• Batch Operating System
  • There is no direct communication between the computer and the OS.
  • There is an intermediate, the Operator.
  • The operator distributes the work into batches.
• Real-Time Operating System
  • The processing time is very small between the user’s command and the output such that there is no operator.
• Time-Sharing Operating System
  • Multiple people at various computers can use a program at the same time.
• Distributed Operating System
  • When two or more systems are connected to each other and one can open each other's files.
• Embedded Operating System
  • These special Operating systems are built into larger systems.
  • They are limited to single specific functions like an ATM.
• Network Operating System
  • They have one main server which is connected to other client servers.
  • It provides a secure operating system for working with multiple users.