Dec 072012

Environmental pollution can simply be defined as the addition of any unwanted or undesirable changes in the physical and biological characters of the environment. As a result of pollution, human life, useful organisms, living conditions, environment, ecosystem, raw materials etc. are being greatly affected due to which they are being badly damaged. This can even lead to their permanent destruction. Various human activities have resulted in the phenomenon of environmental pollution.


Pollutants are the chemical substances or any other things which change the natural balance of the environment and thus result in pollution. These pollutants get accumulated or collected in the environment in huge quantities due to different human activities. Pollutants stimulate, initiate or terminate the vital reactions of an organism. These activities may also bring about changes in the organisms and thus entire ecosystem may also be modified.

Types of Pollutants
According to their degradability, pollutants can be classified into two different types which are listed and described below:

  1. Degradable (Bio-degradable) pollutants: Domestic sewage, cloth, paper, wood etc. lie under degradable pollutants because they can easily be decomposed by the microorganisms present in the environment. However, the decomposition becomes difficult when such materials get accumulated in the environment in a large quantity.
  2. Non-degradable pollutants: Non-degradable pollutants are those pollutants which are neither decomposed by microorganisms nor do they break down by physical and chemical agents which are present in the environment. There is no treatment in nature for their recycling. Therefore, they continue to be accumulated in the nature and occupy large useful space on the earth. For example, aluminium cans, plasticwares, compounds of mercury, Dichloro Diphenyl Trichloroethane (DDT), glass etc. Non-degradable pollutants not only accumulate in the environment but pass from one organism in the food chain to another until it reaches the last trophic level. During this transport, the amount of pollutants continues to increase with each level. This is called biomagnification. The pollutants from more toxic substances come in combination with other substances when they pass through different trophic levels. Such substances are harmful and even kill the biotic components of the ecosystem.
Dec 062012

C (Brain) Virus:

C (Brain) virus was created by Pakistani brothers Amjad and Basit Alvi in the year 1985 A.D. at Lahore. Originally, it was created and designed to prevent unauthorized use of software sold by ‘Alvis’ Brain computer shop at Lahore, Pakistan. It was put into programs like Lotus 123 and WordStar and sold at heavy discounts to foreign tourists. Once the host used the infected disk, it became the carrier of the virus and copied itself quickly to

uninfected computers and diskettes. The virus, hiding in the boot sector replicated quickly and within months it spread throughout the world of personal computers. Later, various strains of this computer virus appeared which were fatal and malicious.

The Stone: The Stone affects the boot sector computers. It affects the Master Boot Record containing partition table, in hard disks. This virus is written in two sections – the resident portion and the installation portion.

The Vienna-648 Virus: The Vienna-648 virus is probably the simplest file infector virus ever created. It is not very efficient and can be written in far less number of instructions. It infects COM files, increasing their size by 648 bytes by appending its code at the end of the file. It doesn’t infect files having size less than 10 bytes. It is also known as the 1-in-8 virus, since on every eighth infection, it creates an instruction for rebooting the computer. Due to this, the file becomes unexecutable and the computer reboots. In case this happens with COMMAND.COM, the computer never boots because every time COMMAND.COM gets recalled and tries to reboot the computer.

The 8290 (Print Screen) Virus: This virus is a boot sector infector. This virus checks for the word, ‘8290 hex’ at a certain place in the boot record. If the word is not present, it won’t be able to affect the computer and its data and instruction. Due to this reason, it is called the 8290 virus. It moves the original boot record to the 11th sector on the floppies and 114th sector on 20 MB hard disks and then transfers its own programs as the boot record.

The Joshi Virus: The Joshi virus is one of the intelligent types of viruses which use stealth techniques in order to baffle affected hackers. This virus affects the Master Boot Record which contains the partition table in hard disks. On 5th January of every year, the virus gets activated. Due to its activation, the whole computer system gets hanged and a message is displayed as “type Happy Birthday Joshi”. The computer can be saved from hanging and it can be used again if the use types the message “Happy Birthday Joshi” in his hanged computer.

The Bloody Virus: The Bloody Virus is also taken as the reincarnation of the Stone virus. This virus affects the Master Boot Record of hard disks which contains the partition table. It was modeled after the Stone virus.

The Ping-Pong Virus: The Ping-Pong virus affects the boot sector of hard disks. The virus gets activated in every 30 minutes and displays a bouncing dot on the monitor of the computer. The dot passes through any text that is displayed on the screen. This virus has no other major effect rather than the creation of 1 KB bad sector where it places the original boot sector.

The Dark Avenger: The Dark Avenger is one of the most dangerous and infectious viruses. Once it infects a disk, it becomes too much difficult to remove it from the disk. It affects the EXE and COM files by attaching itself to the end of the file and puts a JMP instruction at the start of the file. It is a memory resident virus and becomes a resident when an infected file is run. The message “Program too big to fit in memory” is displayed on the screen and the computer gets hanged. The size of the infected files are increased in size by 1800 bytes.