Computer Programming

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echo "enter the value of a"

read a

echo "enter the value of b"

read b

c=`expr $a + $b`

echo "the sum of a and b is $c"

Or, alternatively, one could also...

#!/bin/sh

A=5

B=10

C=`echo "$A + $B"|bc -l`

echo "$A + $B = $C"

The above examples illustrate the use of back ticks to fork a child process in shell, however the first example uses the 'expr' command to perform the arithmetic while the second example uses the 'bc' command to perform the calculation. As is nearly always the case in Unix or Linux, there are multiple methods of arriving at the same correct solution.

While the wonderful and all powerful Perl language is perhaps, technically, not a shell, it is theoretically possible to accomplish this goal in Perl as well. Let me see now, to make this example as educational as possible, I'll use a couple of subscripts of the array @array to store our values and an off-the-shelf printf function to display the results of our calculations...

perl -e '@array = (5, 10); printf("%s + %s = %s\n", $array[1], $array[0], ($array[0]+$array[1]));'

As the purpose of this site is to teach, I briefly entertained and then discarded a notion to shoot for maximum obfuscation. Larry, Randy and Nathan will be proud of me I hope. :)

Naturally, there are numerous other ways to accomplish this goal in Linux.

[Eating] A Pie:

Abstraction: grouping some data and behaviors into a programming unit with semantic similarity (not randomly), e.g, class, struct

Polymorphism: different object with the same name (same name of a method, variable, but in more than 1 form)

Inheritance: the most important characteristics of an OO language (Object base language would not have this one). It allows a derived class to inherit the data and behaviors from the base class(es), as if those data and behaviors are defined within.

Encapsulation: or information hiding. Object has data members that no one outside of the same class would know what type or shape they are. It also applied to the behaviors.

A third generation programming language in essence refers to any high-level

language (except for say, database languages such as SQL). Some well-known

examples are:
PHP, ASP, C, C++, Java, Javascript,

Perl, Python, Pascal, Fortran,

etc.

A fourth generation (programming) language (4GL) is a grouping of programming languages that attempt to get closer than 3GLs to human language, form of thinking and conceptualization.

For example, a typical 4GL command is

FIND ALL RECORDS WHERE NAME IS "SMITH"

include

#include

void main()

{

int x, y, temp;

printf("Enter the value of x and y ");

scanf("d", &x, &y);

printf("Before Swapping x = %d\ny = %d\n",x,y);

temp = x;

x = y;

y = temp;

printf("After Swapping x = %d\ny = %d\n",x,y);

getch();

return 0;

}

Do you happen to know what a flow-chart is?

A bit. Logical and or. Switch on or off. Answer yes or no.

A bit
Each 1 or 0 used in the representation of computer data can be used to present information to you, in order that you may learn it, especially the syntax and forms of the English language, so that when you present questions to global forums where computers also interpret the 1's & 0's to present to people, your question will be understood by those experts whose assistance you so plainly require.

he High Level Language is basically classified into 3 types namely:

1. Procedural Language
2. Functional Language
3. Object Oriented Language

Procedural Language:

The most common high-level languages today are procedure-oriented languages. In these languages, one or more related blocks of statements that perform some complete function are grouped together into a program module, or procedure, & given a name such as "Procedure A." If the same sequence of operations is needed elsewhere in the program, a simple statement can be used to refer back to the procedure. In essence, a procedure is just a mini-program. A large program can be constructed by grouping together procedures that perform different tasks.

Procedural languages allow programs to be shorter and easier for the computer to read, but they require the programmer to design each procedure to be general enough to be used in different situations.

Functional Language:

Functional languages treat procedures like mathematical functions and allow them to be processed like any other data in a program. This allows a much higher and more rigorous level of program construction. Functional languages also allow variables-symbols for data that can be specified and changed by the user as the program is running-to be given values only once. This simplifies programming by reducing the need to be concerned with the exact order of statement execution, since a variable does not have to be redeclared, or restated, each time it is used in a program statement. Many of the ideas from functional languages have become key parts of many modern procedural languages.

Object Oriented Language:

Object-oriented languages are outgrowths of functional languages. In object-oriented languages, the code used to write the program and the data processed by the program are grouped together into units called objects. Objects are further grouped into classes, which define the attributes objects must have.

A simple example of a class is the class Book.

Objects within this class might be Novel and Short Story. Objects also have certain functions associated with them, called methods. The computer accesses an object through the use of one of the object's methods. The method performs some action to the data in the object and returns this value to the computer. Classes of objects can also be further grouped into hierarchies, in which objects of one class can inherit methods from another class. The structure provided in object-oriented languages makes them very useful for complicated programming tasks.

Advantages

Sharing devices such as printers saves money. Files can easily be shared between users. Network users can communicate by email. Security is good - users cannot see other users' files unlike on stand-alone machines. A file server is easy to back up as all the data is stored in one place. A computer allows a person to manipulate data easily and quickly, create text documents, edit them, print them, manipulate images, print them, send text and images over the Internet, download information over the Internet, interact with other people easily from home, keep records of transactions, activities, plan trips, and generally do far more than a person without a computer. Computers are very useful to make everyday life a lot easier. You can check the weather, email, search items, buy things type papers and much much more. You can also play games and post blogs and other stuff. People use computers in many ways. Can be used in business, inventions and scanners.

Computers help children to be in control of their experience, to set their own pace, and to select the level of challenge with which they feel comfortable. Computers help children to use all of their senses to extract information. Computers fascinate kids and can draw their full attention, which often results in a deeper focus and concentration. Computers enable children to learn through creating, just as they gain hands-on knowledge and understanding when they build forts, make up stories, and paint, increase their skills. Good educational software enables children to develop and practice a broad range skill. It can help them learn, for example, about letters, numbers, shapes, colours, and rhythm. Good software can also help children develop their understanding of cause and effect, higher order problem solving, procedural thinking, and creative expression. Today, the wide range of multimedia available for kids in India is really amazing. Computers are helpful because they offer a wide range of functions and services that are not available anywhere else. There are four main uses: word processing, internet/communications, digital video/audio composition, and desktop publishing.

Disadvantages

The teenagers of today's society have changed dramatically due to the Computer. Nowadays, the majority of teenagers have a PC and it has played a key role in their lives. Teenagers need to be equipped with knowledge of computer technology, as most things in life require the use of computers. One disadvantage of owning a computer is the information that students can access from the Internet. The Internet has also made the youth of today quite lazy, especially in terms of their education. If a student needs to research information for school, they merely access a relevant site and download the information, rarely paying attention to what is written. Purchasing the network cabling and file servers can be expensive. If the file server breaks down the files on the file server become inaccessible. Viruses can spread to other computers throughout a computer network. There is a danger of hacking, particularly with wide area networks.

Computers are very engaging on children as well as adults. Kids with access to software that is not age appropriate may be exposed to such negative influences as violence, strong language, and over-stimulation from fast-action graphics.