Advantages of E-Mail:

·         Cheaper than ordinary mail

·         No need to go out to post office or mailbox to post bulky documents

·         The same message can be sent to groups of people simultaneously.

·         Addresses of regular recipients can be stored on your computer and retrieved automatically.

·         Files, graphics or photographic images can be sent in compressed forms.

Functions of an Operating System:

1.      Resource Allocation and Scheduling

2.      Memory Management

3.      Backing-store management

4.      Input/Output Control

5.      Interrupt Handling (Errors Handling)

6.      Operator interface (Accepts commands and responds to them)

7.      Security (assign login codes and passwords to users)

8.      Accounting Facilities (no. of printed pages, disk space used etc)

9.      Utilities

Compiler verses Interpreter:

Compiler

1.      A compiled program will almost run faster than an interpreted program.

2.      The object program (the machine code generated by the compiler) may be saved on disk and run as many times as required without being recompiled.

3.      A compiler can give more helpful error messages: if, for example, a keyword (reserved word) is misspell all through the program, an interpreter will only find the first instance, whereas a compiler will list them all.

4.      A compiler will check the syntax of the entire program, whereas an interpreter will only check the syntax of the statements that are executed during that particular run of the program. Certain branches of the program may therefore not be checked until very thorough testing takes place.

5.      Commercially produced software can be sold in the form of object code, thus preventing purchasers’ from listing the source code or making modifications to it.

Interpreter:

1.      Interpreters are very convenient for program development, since making modifications does not mean that the whole program has to be reloaded and recompiled, which can take a considerable time. Many interpreters will allow a program to run up to the point where an error occurs, let the programmer fix the error and then continue to run the program form that point.

2.      An interpreter is simpler to write and is usually cheaper to buy than a compiler.

Adding and deleting the records on a serial file

If one or more records has to be added to a serial file, there is no problem, and the new records can simply be appended to the end of the file.

Deleting a record is more complex. It is easy to understand the problem if we imagine the file is held on magnetic tape, and understand that in any particular program run you can either read from the tape or write to the tape. To find the record to be deleted, the computer has to read the tape form the beginning; but once it has found it, it cannot backup and ‘wipe’ just at that portion of the tape occupied by the record, leaving a blank space. The technique therefore is to create a brand new tape, copying over all the records up to the one to be deleted, leaving that one off the new tape and then copying over all the rest of the records.

Adding and deleting the records on a sequential file

 With sequential file, all the records on the tape (or disk) are in order, perhaps of employee number, so just adding a  new record on the end is not good at all. Of course the records could then be sorted by sorting is a very time consuming process. The best and ‘correct’ way is to make a new copy of the file, copying over all records till new one can be written in its proper place, and then copying over the rest of the records. It’s exactly as if you had just made a list on a nice clean sheet of paper of all the students in the class in order of surname, and then discovered you had left out carter, A.N. the only way to end up with the perfect list is to copy it out again, remembering to include Carter this time.

Why Robots Are Used?

      1.     Robots can work in environment hazardous to humans, or perform dangerous tasks such as disarming live bombs, working in a radioactive environment or sending information back form the surface of Mars.

     2.      They can tirelessly perform repetitive and monotonous tasks, lift heavy loads and reach ling distances. They are used for example, by the US Navy to scrape and repaint ships.

     3.      Labour costs can be substantially reduced, and robots are now widely employed in car manufacturing as well as many other industries, including printing and publishing. Robots can carry tons of paper coming off presses, bind and trim books and apply books covers. It has been estimated that each industrial robot will replace an average of six workers.

      4.      Quality of work is consistent. A robot is never distracted or bored, never loses concentration or makes a mistake.

      5.       Increased productivity. Robots will work for 24 hours a day, work faster