THE ORIGIN OF C++

The C programming language was developed at AT&T for the purpose of writing the operating system for the PDP-11 series of computers which ultimately became the UNIX operating system. C was developed with the primary goal of operating efficiency. Bjarne Stroustrup, also of AT&T, developed C++ in order to add object oriented constructs to the C language. Because object oriented technology was new at the time and all existing implementations of object oriented languages were very slow and inefficient, the primary goal of C++ was to maintain the efficiency of C.

C++ can be viewed as a traditional procedural language with some additional constructs. Beginning with C, some constructs are added for object oriented programming and some for improved procedural syntax. A well written C++ program will reflect elements of both object oriented programming style and classic procedural programming. C++ is actually an extendible language since we can define new types in such a way that they act just like the predefined types which are part of the standard language. C++ is designed for large scale software development.

C++ syntax

By definition, syntax is the rules governing the formation of statements in a programming language. In other words, it is the specific language (code) you use to turn algorithms into programs and specific rules you have to follow when programming with C++. As you will find out, if you make one small mistake when writing code, the compiler will notify you of the syntax error when you try to run it. C++, like all languages, is very picky when it comes to syntax. Let's look at a simple example program written in C++.

// BEGIN PROGRAM

// Program to calculate the average of 4 integers

#include <iostream.h>            // header file for input/output stream
#include <conio.h>                 // header file for standard input/output

int main( )
{
    int number1, number2, number3,number4;    // declaration of variables
    float average;
    clrscr();                                            // Clear the output screen
    cout << endl << endl;
    cout << "Enter first integer: ";
    cin >> number1;
    cout << "Enter second integer: ";
    cin >> number2;
    cout << "Enter third integer: ";
    cin >> number3;

    cout << "Enter third integer: ";
    cin >> number4;

    average = (number1 + number2 + number3+number4) / 3.0;           // calculates the average
    cout << "The average of the three integers is: " << average << endl;

    getch();                                            // Wait for a character expression from keyboard
    return 0;
}    // end main( )

For now, notice how each executable statement in the program is ended with a semi-colon. Every executable statement must always be terminated with a semi-colon, which signals that it is the end of the statement. Any code placed after // will not affect the code; // is used for comments and documentation. Also notice that text is always enclosed in parentheses. Let's dig deep into the code to find out why you need to use certain code statements.

• cout - console output - It is simply letting the compiler know that something is being sent into the output stream (normally the screen)
• << - insertion operator - cout and the insertion operator go hand and hand; you must use it whenever you issue a cout command
• cin - console input - It is simply letting the compiler know that something is being sent into the input stream (normally into the memory of a computer)
• >> - extraction operator - cin and the extraction operator go hand and hand; you must use it whenver you issue a cin command
• endl - end line - basically the same as pressing the return key in a text editor; returns down to the next line