Chapter 1. Getting Start

1.1 Writing a Simple C++ Program

main function: Every C++ program contains one or more functions, one of which must be named main. They operating system runs a C++ program by calling main.

A function definition has four elements: a return type, a function name, a parameter list enclosed in parentheses, and a function body.

built-in type: the type defined by the language.

The value returned from main is a status indicator, a return value of 0 indicate success; a nonzero return has a meaning that is defined by the system. Ordinarily a nonzero return indicates what kind of error occurred.

1.1.1 Compiling and Executing Our Program

The value returned from main is accessed in a system-dependent manner. To obtain the status by:

UNIX System
$ echo $?
Windows System
$ echo %ERRORLEVEL%

1.2 A First Look at Input/Output

iostream library: an extensive standard library that provide IO in C++, the istream and ostream, which represent input and output streams respectively, fundament to the iostream library.

• cin: standard input;

• cout: standard output;

• cerr: standard error for warning and error message;

• clog: for general information about the execution of the program;

expression: an expression yields a result and is composed of one or more operands and on operator.

endl: a special value called a manipulator, writing endl has the effect of ending the current line and flushing the buffer associated with that device.

namespace: namespace allow users to avoid inadvertent collisions between the names that defined and used of those same names inside a library.

1.3 A Word about Comments

comments: comments help the human readers of the programs, they are typically used to summarise an algorithm, identify the purpose of a variable, or clarify an otherwise obscure segment of code.

There are two kinds of comments in C++: single-line and paired. A single-line comment starts with a double slash (//) and ens with a newline. The paired uses two delimiters (/* and */) that are inherited from C.

1.4 Flow of Control

1.4.1 The while Statement

A while statement repeatedly executes a section of code so long as a given condition is true.

while (condition)
    statement

A condition is an expression that yields a result that is either true of false.

1.4.2 The for Statement

The pattern, using a variable in a condition and incrementing that variable in the body, is called for statement.

for(definition; condition; incremention)
    statement

1.4.3 Reading an Unknown Number of Inputs

An istream becomes invalid when it hits end-of-file or encounter an invalid input, such as reading a value that is not an integer. An istream that is in an invalid state will cause the condition to yield false.

Entering an end-of-file: control-z in Windows and control-d in UNIX.

1.4.4 The if Statement

C++ provides an if statement that supports conditional execution.

C++ uses = for assignment and == for equality. Both operators can appear inside a condition. It is a common mistake to write = when you mean == inside a condition.

1.5 Introducing Classes

In C++ we define our own data structures by defining a class. Every class define a type, and the type name is the same as the name of the class.

member function: a function that is defined as part of a class.