C++ (pronounced "see plus plus") is a statically
typed, free-form, multi paradigm, compiled,
general purpose programming language. It is regarded as an
intermediate-level language, as it
comprises both high-level and low level language features.
Developed by Bjarne Stroustrup
starting in 1979 at Bell Labs, C++ was originally named C with Classes, adding object oriented
features, such as classes, and other enhancements to the C programming
language. The language was renamed C++ in 1983. C++ is one of the most popular
programming languages and is implemented on a wide variety of hardware and
operating system platforms. As an efficient compiler to native code, its
application domains include systems software, application software, device
drivers, embedded software,
high-performance server and client applications, and
entertainment software such as Video
games. C++ is also used for hardware design, where the
design is initially described in C++, then analyzed, architecturally
constrained, and scheduled to create a register-transfer level hardware description
language via high level synthesis.
The language began as enhancements to C, first adding
classes, then virtual functions, operator overloading, multiple inheritance,
templates and exception handling, among other features. After years of
development, the C++ programming language standard was ratified in
STRUCTURE OF C++ PROGRAM
C++ uses notation that may appear strange to non
programmers. Let us begin by considering a
simple program that prints a line of text.
1 // our first program in C++
2 #include <iostream>
3 using namespace std;
4 int main ()
5 {
6 cout << "Welcome
to the world of C++ !\n”;
7 return 0; // the program ended successfully
8 }
Output
Welcome to the world of computer
The above program illustrates many features of C++
language. We will look at the program line
by line.
Line 1: // our first program in C++
// the two slash sign are comments and do not have any
effect on the behavior of the program.
The programmer can use them to include short explanation or
observations within the source
code itself. Therefore, the line is a brief description of
what our program is. Another way to write
a comment is to put it between /* and */ but a comment of
this form may span multiple lines.
Line 2: # include <iostream>
Lines beginning with a hash sign (#) are directives for the
processor. They are not regular code
lines with expressions but indications for the compiler’s
preprocessor. In this case the directive #
include <iostream> tells the preprocessor to includes
in the program the iostream standard file.
Line 3: Using name space std;
All the elements of the standard C++ library are declared
within what is called a namespace, the
namespace with the name std. so in order to access its
functionality we declare with this
expression that we will be using these entities. This line
is very frequent inC++ programs that
use the standard library.
Line 4: int main ( )
Is a part of every C++ program. The line corresponds to the
beginning of the definition of the
main function is the point by where all C++ programs start
their execution, independently of its location within the source code. It does
not matter whether there are other functions with other names defined before or
after it- the instruction contained within this function’s will always be the
first ones to be executed in any C++ program. For that same reason, it is
essential that all c++ programs have a main function.
The word main is followed in the code by a pair of
parentheses ( ( ) ). That is because it is a
function declaration: in C++, what differentiate a function
declaration from other types of
expressions are these parentheses that follow its name.
Optionally, these parentheses may
enclose a list of parameters within them.
Line 5 and 8: { }
Within the curly brackets is the body of the main function
( {}). What is contained within these braces is what the function does when it
is executed.
Line 6: cout << “welcome to the world of C++ !
“<<endl;
This line is a C++ statement. A statement is a simple or
compound expression that can actually produce some effect. In fact, this
statement performs only action that generates a visible effect in our program.Cout
is the name of the standard output stream in C++, it instructs the computer to
print on the screen the strings of characters contained between quotation
marks. The semicolon is a statement terminator; every statement must end with a
semicolon.
Line 7: return 0;
The return statement causes the main function to finish.
Other information
The operator << is referred to as the stream
insertion operator. When this program executes, the value to the right of
the operator, the right operand, is inserted in the output stream. The characters
of the right operand normally print exactly as they appear between the double
quotes.Notice however, that the characters \n are not printed on the screen.
The backslash (\) is called an escape
character. It indicates that “a special” character is to be output. When
a backslash is
encountered in a string of characters, the next character
is combined with the backslash to form an escape sequence. The escape
sequence\n means newline. It causes the cursor (i.e the current screen
position indicator) to move to the beginning of the next line on the screen.
Some other common escape sequences are listed below.
Escape
Sequence
Description
\n Newline. Position the screen to the beginning of the
next line.
// Forward slash. Used to insert comment inside program
\\ Backslash. Used
\r Carriage return. Position the screen cursor to the
beginning of the current line;
do not advance to the next line.
\t Horizontal tab. Move the screen cursor to the next tab
stop.
\a Alert. Sound the system bell
\” Double quote. Used to print double quite character
.
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