C++ Basics Elements

C++ Basics Elements

 

A C++ program is a collection of one or more subprograms, called functions. Roughly

speaking, a subprogram or a function is a collection of statements, and when it is

activated, or executed, it accomplishes something. Some functions, called predefined or

standard functions, are already written and are provided as part of the system. But to

accomplish most tasks, programmers must learn to write their own functions.

 

Every C++ program has a function called main . Thus, if a C++ program has only one

function, it must be the function main . Until Chapter 6, other than using some of the

predefined functions, you will mainly deal with the function main . By the end of this

chapter, you shall have learned how to write the function main .

Example 01:

The following is a sample C++ program.

// This is a C++ program. It prints the sentence:

// Welcome to C++ Programming.

#include <iostream>

using namespace std;

int main()

{

cout << "Welcome to C++ Programming." << endl;

return 0;

}

If you execute this program, it will print the following line on the screen:

Welcome to C++ Programming.

 

If you have never seen a program written in a programming language, the C++

program in Example 01 may look like a foreign language. To make meaningful sentences

in a foreign language, you must learn its alphabet, words, and grammar. The same is true

of a programming language. To write meaningful programs, you must learn the pro-

gramming language’s special symbols, words, and syntax rules. The syntax rules tell you

which statements (instructions) are legal, or accepted by the programming language,

and which are not. You must also learn semantic rules, which determine the meaning

of the instructions. The programming language’s rules, symbols, and special words enable

you to write programs to solve problems. The syntax rules determine which instructions

are valid.

 

Programming language: A set of rules, symbols, and special words.

Let us begin with the real C++ programming rules.

Comments

The program that you write should be clear not only to you, but also to the reader of

your program.

Comments are for the reader, not for the compiler. So when a compiler compiles a

program to check for the syntax errors, it completely ignores comments. Throughout this

chapter, comments are shown in green.

 

There are two common types of comments in a C++ program—single line comments

and multiple line comments.

Single line comments begin with // and can be placed anywhere in the line. Everything

encountered in that line after // is ignored by the compiler.

 

Consider the following statement:

cout << "7 + 8 = " << 7 + 8 << endl;

You can put comments at the end of this line as follows:

cout << "7 + 8 = " << 7 + 8 << endl; //prints: 7 + 8 = 15

 

Multiple line comments are enclosed between /* and */. The compiler ignores anything

that appears between /* and */.

 

For example, the following is an example :

 

/*

You can include comments that can

occupy several lines.

*/

 

Identifiers

A C++ identifier consists of letters, digits, and the underscore character ( _ )

and must begin with a letter or underscore.

Identifiers can be made of only letters, digits, and the underscore character; no other

symbols are permitted to form an identifier.

C++ is case sensitive—uppercase and lowercase letters are considered different. Thus,

the identifier NUMBER is not the same as the identifier number . Similarly, the

identifiers X and x are different.

In C++, identifiers can be of any length.

 

 

Data Types

The objective of a C++ program is to manipulate data. Different programs manipulate

different data. A program designed to calculate an employee’s paycheck will add, subtract,

multiply, and divide numbers, and some of the numbers might represent hours worked and

pay rate. Similarly, a program designed to alphabetize a class list will manipulate names. You

wouldn’t expect a cherry pie recipe to help you bake cookies. Similarly, you wouldn’t use a

program designed to perform arithmetic calculations to manipulate alphabetic characters.

Furthermore, you wouldn’t multiply or subtract names. Reflecting these kinds of underlying

differences, C++ categorizes data into different types, and only certain operations can be

performed on particular types of data.

 

 

They’ll never be happy together. He’s not her type.

Overheard at a Cocktail Party

 

int DATA TYPE

Integers in C++, as in mathematics, are numbers such as the following: -6728, -67, 0, 78, 36782, +763.

 

 

Variables

 

A C++ variable can hold a number or data of other types.

Every variable in a C++ program must be declared. When you declare a

variable you are telling the compiler—and, ultimately, the computer—what

kind of data you will be storing in the variable.

 

Examples:

int number_of_bars;

double one_weight, total_weight;

 

When there is more than one variable in a declaration, the variables are

separated by commas. Also, note that each declaration ends with a semicolon.

 

Majokta

Kaize Trademark

By Majokota

Copyright 2016 Majokota Society.