OSI Model

Special features of the computer

• Various machines have been invented by man to transform data into information. Among them, the computer commands a vital role. Many reasons have influenced to gain this important position and given below are some of the main reasons.
• Speed – The computer is a machine which operates very fast. A task or calculation which takes a long time to be completed through other means can be completed in a very short period using the computer.
• Accuracy – The computer is a machine which operates with a very high rate of accuracy. If there is any error in the operation of the computer, such errors occur due to the errors of the given instructions and data. When preparing a program for the computer, it is a fundamental responsibility of the person who prepares the instructions to ensure the accuracy of it.
• Efficiency – As it is a machine a computer which is installed in a suitable environment can be operated in the same speed continuously without any rest for any duration you need. This will not feel monotony, fatigue and loss of concentration as human beings.
• Versatility – The ability to engage in a number of tasks is a special feature of the computer. Just after finishing one task, the computer can perform another completely different task with the same efficiency.
• Storing and Retrieving – The data and information can be saved in the computer as long as we wish and it can be retrieved instantly when we need them. This is another special feature of a computer.
• No intelligence – Intelligent computers have not been created so far and all computers operate according to the commands or programs given by human beings.
• No feelings – A computer is just another machine we use. Computers do not get feelings such as isolation, loneliness and exhaustion. Therefore, we can use computers to get our work done as we wish.

Basic functions of a computer

• Input or inserting data and instructions – Input can be defined as inserting data and instructions needed for a computer.
• Processing – The process of converting data inserted to the computer to information as required can be defined as processing.
• Output or retrieving data or information – Giving the processed data and information to the external force is done under output.
• Storing data or information – Data and information are stored in a way that they can be reused later as required. This is done under storing.
• Controlling – The functions of a computer system and its various devices should be controlled properly. Under controlling the controlling activities done by computer system are considered.

Classification of Computers

According to the generation

• First generation computers - Vacuum tubes were used to design computers of this generation.
• Second generation computers - Transistors were used to design computers of this generation.
• Third generation computers - Integrated Circuits (IC) were used to design computers of this generation.
• Fourth generation computers - Microchips or Microprocessors were used to design computers of this generation.
• Fifth generation computers - Computers that are supposed to have the thinking ability are called fifth generation computers. Scientists are trying hard to develop the fifth generation computers using 'Artificial Intelligence'.

According to the size

• Super computers - Computers which are designed for a specific purpose with very high performance and capabilities are called as such. 
• Mainframe computers - These are the large scale computers. 
• Mini computers - Medium size computers can be called mini computers. 
• Micro computers - Extremely small computers that can be called micro computers.

According to the technological development

• Personal computers (PCs) - Computers designed for individual's use are called personal computers and this type of computers has been widely developed now. Personal computers are also known as ' Desktop Computers'.
• Laptop computers - These are portable computers designed to be carried about. These are known as the 'Note book computers' or 'Portable computers'.
• Palmtop computers - These are the computers that can be held on palm. Palmtops are also called 'Personal Digital Assistants' (PDAs).
• Work station computers - The name 'Workstation computers' is used for desktop computers made with high capacities. These are widely used to design more complex graphic designing and 3D animations and also serve as server computers.

According to the purpose

• Computers designed for usual and day - to - day activities are called General Purpose Computers.
• Computers designed for special purposes such as scientific experiments, battle operations, discovery of oil rigs etc.. are called Special Purpose Computers.

According to the design technology

• Digital computers - Computers designed by using the binary digital number system are called digital computers.
• Analog computers - Computers which are designed considering the physical data such as temperature, thrust, and pressure are called analog computers.
• Hybrid computers - A combination of the above two types of computers can be called hybrid computers.

Computer Games

Sports have got a special place in our daily life. It not only provides enjoyment, but also increase physical and mental solace. Today the computer with its related equipment are used as gaming equipment. So, as mentioned earlier, it not only provides enjoyment but also helps to increase knowledge in various fields.
When we play computer games, it is an important fact that games can be set according to an individual's age, knowledge level or skill level. Especially games such as chess can be highlighted here.
Such sports will enhance our intelligence, skills to take quick decisions and creativity.
Computer games help to improve the knowledge, creativity and analyzing skills not only on mathematics, science and technology but also on many other subjects like language, music and art. Computer games are popular media that helps mental relaxation and reducing physical fatigue.
However, addiction to computer games and gambling are the bad sides of computer games.

Identify the various categories of website users and describe in detail.

• Expert users (meaning with extended experience in the application) expects advance features and capabilities. They will want more customization options. Since they have a stable mental model of the application structure they feel free to explore the application and try new things. They will not be too worried about making mistakes since they feel secure that they will know how to bypass them.
• Novice users: on the other hand, are new to the system and will need a simple and basic interface. Since they are new in the system they will expect more secure ways of doing things in the system (for example they will choose the templates or wizards to do their first steps in the system). Novice users' interface should provide simple ways to achieve important frequently performed tasks. When designing to novice users we should remember what the main use cases and don't shadow them with unnecessary features. 
• Users with special needs: Users with special needs who are not sufficiently visually impaired to require assisted technologies can still be frustrated by poor contrast, problematic color schemes, or tiny, unreadable text. Up to 10% of men are color blind to some extent, and the increasing number of older users is less likely to have 20/20 vision than those designing the pages.

Email

*What is meant by attachment facility?
  The attachment information with e-mail.
  These attached information can be sent as attached files.
  The files may be text files or document files.
  By the attachment facility we can send any number of files with email.
*What is the use of email dictionary?
  While sending email the email dictionary helps to know the meaning of the word, if we need.
*What is the use of spell check?
  It helps to make spelling corrections in the email which we typed.
*What is the use of treasures?
  The facility which gives different words in similar meaning.
*What is mean by inbox?
  Inbox is which we receives all the emails to a person who holds email address.
*How can we erase the unwanted email?
  Select the unwanted emails and press the delete button.