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C++ Review

Lecture 1

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Outline

C++ basic features Programming paradigm and statement syntax

Class definitions Data members, methods, constructor, destructor

Pointers, arrays, and strings Parameter passing in functions

Unlike the text book, in this course, we willnot use Templates

Friend

Operator overloading

I/O streams An example on file copy

Makefile on unix

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Functions & Memory

Every function needs a place tostore its local variables.

Collectively, this storage is called

the stack

This storage (memory aka RAM),

is a series of storage spaces andtheir numerical addresses

Instead of using raw addresses,

we use variables to attach a

name to an address

All of the data/variables for aparticular function call are located

in a stack frame

Memory

location

void aFunc(int x, int y)

{double d1, d2;

int i;}

x

y

d2

d1

i

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Modular Concept - Problems

Advantages

Disadvantages

Decoupled Data and Operations The resulting module structure is oriented on the

operations rather than the actual data

The defined operations specify the data to be

used. E.g.: in previous example,

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Object-Oriented Concept (C++)

Objects of the program interact by sending messages to each

other

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Basic C++

Inherit allC syntax Primitive data types

Supported data types: int, long, short, float,double, char, bool, and enum

The size of data types is platform-dependent

Basic expression syntax Defining the usual arithmetic and logical operations such

as +, -, /, %, *, &&, !, and ||

Defining bit-wise operations, such as &, |, and ~

Basic statement syntax If-else, for, while, and do-while

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Basic C++ (cont)

Add a new comment mark // For 1 line comment

/* */ for a group ofline comment

New data type Reference data type &. Much likes pointer

int ix; /* ix is "real" variable */

int & rx = ix; /* rx is "alias" for ix */

ix = 1; /* also rx == 1 */

rx = 2; /* also ix == 2 */

const support for constant declaration, justlikes C

Use this when

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Two labels:publicandprivate Determine visibility of class members

A member that ispublicmay be accessed by any method in

any class

A member that isprivate may only be accessed by methods

in its class Information hiding

Data members are declaredprivate, thus restricting access

to internal details of the class

Methods intended for general use are madepublic

Information Hiding in C++

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A constructoris a special method that describes how aninstance of the class (called object) is constructed

Whenever an instance of the class is created, itsconstructor is called.

C++ provides a default constructorfor each class, whichis a constructor with no parameters. But, one can definemultiple constructors for the same class, and may evenredefine the default constructor

How to distinguish them?

E.g. How to create IntCell with storedValue=10?

storedValue=0?

Hint: C++ has an operator new

Constructors

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Pointers

Apointeris a variable which

contains addresses of other

variables

Accessing the data at the

contained address is calleddereferencing a pointer or

following a pointer

n(4096)

y

(4100)

x

(4104)

4096

7pointer

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Interface and Implementation

In C++ it is more common to separate the classinterface from its implementation.

The interface lists the class and its members (data

and functions).

The implementation provides implementations ofthe functions.

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class IntCell

{

public:

explicit IntCell( intinitialValue = 0 );

int read( ) const;

void write( int x );

private:

int storedValue;

}

IntCell::IntCell( int initialValue )

: storedValue ( initialValue ){ }

int IntCell::read( ) const

{ return storedValue; }

void IntCell::write( )

{ storedValue = x; }

The interface is typically placed in a file that ends with .h. Themember functions are defined as:

ReturnType FunctionName(parameterList);The implementation file typically ends with .cpp, .cc, or.C. The

member functions are defined as follows:

ReturnType ClassName::FunctionName(parameterList)

{ }

IntCell.h IntCell.cpp

Scopingoperator

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int f(int x) { cout

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A reference variable is different from a pointer

A pointer need NOT be initialized while defining, but a

reference variable should always refer to some other

object.int * p;

int m = 10;int & j = m; //valid

int & k; //compilation error

Reference Variables (cont)

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A pointercan be assigned a new value to point at adifferent object, but a reference variable always refers tothe same object.Assigning a reference variable with anew value actually changes the value of the referredobject.int * p;

int m = 10;int & j = m; //valid

p = &m; //p now points at m, p=address of m

int n = 12;

j = n; // the value of m is set to 12. But j still refers to m,not to n.

cout

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Class and Objects

point.cc, point.cpp

void Point::setX(const int val) {

_x = val;

}

void Point::setY(const int val) {

_y = val;

}

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Main program

main.cc, main.cppint main(int argc, char* argv[]) {

Point apoint;

apoint.setX(1); // Initializationapoint.setY(1);

//

// x is needed from here, hence, we define ithere and// initialize it to the x-coordinate of apoint

//

int x = apoint.getX();

}

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Standard Input/OutputStreams

Stream is a sequence of characters

Working with cin and cout

Streams convert internal representations to

character streams >> input operator (extractor)

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CountChars.cpp (Output)

cout

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Files

#define associates the name of the streamwith the actual file name

fail() function - returns nonzero if file fails

to open Program CopyFile.cpp demonstrates the use

of the otherfstream functions

get, put, close and eof

Copy from one file to another

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CopyFile.cpp (Opening OutputFile)

outs.open(outFile);if (outs.fail()) {

cerr

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CopyFile.cpp (Copy Line by Line)

// Copy each character from inData to outData.lineCount = 0;

do{

if (copyLine(ins, outs) != 0)

lineCount++;

}while (!ins.eof());

// Display a message on the screen.cout

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CopyFile.cpp (copyLine procedure)

// Copy one line of text from one file to another

// Pre: ins is opened for input and outs for

// output.

// Post: Next line of ins is written to outs.

// The last character processed from

// ins is ;// the last character written to outs

// is .

// Returns: The number of characters copied.

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CopyFile.cpp (Character Reading)

int copyLine (ifstream& ins, ofstream& outs){// Local data ...

const charNWLN = '\n';

char nextCh;

int charCount = 0;

// Copy all data characters from stream ins to// stream outs.

ins.get(nextCh);

while ((nextCh != NWLN) && !ins.eof()){

outs.put(nextCh);

charCount++;

ins.get (nextCh);} // end while

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CopyFile.cpp (Detection of EOF)

// If last character read was NWLN write it

// to outs.

if (!ins.eof())

{

outs.put(NWLN);

charCount++;}

return charCount;

} // end copyLine