Lecture 3: The parts of a C++ program

Professor: Dr. Miguel Alonso Jr.

Fall 2008

CGS2423/COP1220

C++ Anatomy

The Parts of a C++ Program

// A simple C++ program#include <iostream>using namespace std;

int main(){

cout << “Programming is great fun!”;return 0;

}

Comment: ignored by the compilerPreprocessor

Directive: sets up the code for the compiler

Namespace: used to organize the names of program entries, such

as variables, functions, and objects

Function: a group of one or more programming

statements that collectively have a

name

Left-brace: part of the C++ syntax and encloses all the

statements that make up a function

Statement: consists of cout object, <<

operator, and string literal or constant,

conluded by ;

Return statement: indicates the program executed succesfully

The cout Object

cout is used to produce console output, hence cout!

It is classified as a stream object, which means it works with a stream of data, such as a string literal (stream of characters)

Run Example << is the stream insertion operator

The item immediately to the right of << is sent to cout for display

Program 2-2

Can be used to send more than one item out.

// A simple C++ program#include <iostream>using namespace std;

int main(){

cout << “Programming is “ << “great fun!”;

return 0;}

Program 2-3

Output can also be broken up into many statements, but still shows up on a single line.

// A simple C++ program#include <iostream>using namespace std;

int main(){

cout << “Programming is ”;cout << “great fun!”;return 0;

}

Program 2-4

Unless otherwise specified, the output of cout is displayed on a continuous stream. Sometimes, this is not desireable// A simple C++ program#include <iostream>using namespace std;int main(){

cout << “The following items were top sellers”;cout<<“during the month of June:”;cout<<“Computer Games”;cout<<“Coffee”;cout<<“Apirin”;return 0;

}

Solution: start a new line Stream manipulator : endl (end-L or end line) Newline escape sequence: \n// A simple C++ program#include <iostream>using namespace std;int main(){

cout << “The following items were top sellers”<< endl;cout<<“during the month of June:” << endl;cout<<“Computer Games” << endl;cout<<“Coffee” << endl;cout<<“Apirin” << endl;return 0;

}

// A simple C++ program#include <iostream>using namespace std;int main(){

cout << “The following items were top sellers\n”;

cout<<“during the month of June:\n”;cout<<“Computer Games\n”;cout<<“Coffee\n”;cout<<“Apirin\n”;return 0;

}

Common Escape Sequences

\a Bell (beep) \b Backspace \n Newline \r Return \t Tab \\ Backslash \' Single quote \" Double quote

The #include directive

Example: #include <iostream> This is a header file that contains information

describing iostream objects, such as cout Part of the input-output stream library Header file contains C++ code and typically

describes complex objects, like cout Later on, we will create our own header files

Variables and Literals

Variables represent storage locations in the computers memory

int number; variable definition Sets up name and type of data the variable will

hold number = 5; variable assignment (integer

literal) number = “5”; string literal

// A simple C++ program#include <iostream>using namespace std;int main(){

int number;

number = 5;cout<< “The value in number is “ << number << endl;return 0;

}

Identifiers

Identifier: programmer-defined name that represents some element of a program Example: variable names

Usually indicates what the variable is used for

Caveat: cannot use C++ key words and must be legal

Identifier Rules

First character must be a – z, A – Z, or an underscore( _ )

After the first character, a – z, A – Z, an underscore, or 0 – 9

Upper and lower are distinct, that is C++ is case sensitive

Integer Data Types

Two general data types: Numeric Character

Number is further broken down integer floating point

Variables declared as integers can only hold whole numbers i.e. 1, 2, 3…

Floating point can store decimal numbers i.e. 4.657, -8.96, 3.5

Concerns when selecting numeric data types

Largest and smallest value that may be stored

How much memory that value uses Signed or unsigned Decimal Precision

Tips

use unsigned Combine same type variable definitions on

one line Use “L” after integer literals if long is needed

Example : number = 32L Uses 4 bytes of memory instead of just 2

Program examples 2-10 and 2-11