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Introduction to C++

Noppadon Kamolvilassatian

Department of Computer Engineering
Prince of Songkla University
1

Contents

s 1. Introduction
s 2. C++ Single-Line Comments
s 3. C++ Stream Input/Output
s 4. Declarations in C++
s 5. Creating New Data Types in C++
s 6. Reference Parameters
s 7. Const Qualifier
s 8. Default Arguments
s 9. Function Overloading 2

1. Introduction

s C++ improves on many of C’s features.
s C++ provides object-oriented programming
(OOP).
s C++ is a superset to C.
s No ANSI standard exists yet (in 1994).

3

2. C++ Single-Line Comments

s In C,
/* This is a single-line comment. */
s In C++,

// This is a single-line comment.

4

3. C++ Stream Input/Output

s In C,
printf(“Enter new tag: “);
scanf(“%d”, &tag);
printf(“The new tag is: %dn”, tag);
s In C++,
cout << “Enter new tag: “;
cin >> tag;
cout << “The new tag is : “ << tag << ‘n’;

5

3.1 An Example

// Simple stream input/output
#include <iostream.h>

main()
{
cout << "Enter your age: ";
int myAge;
cin >> myAge;

cout << "Enter your friend's age: ";
int friendsAge;
cin >> friendsAge;
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if (myAge > friendsAge)
cout << "You are older.n";
else
if (myAge < friendsAge)
cout << "You are younger.n";
else
cout << "You and your friend are the
same age.n";

return 0;
}

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4. Declarations in C++

s In C++, declarations can be placed anywhere
(except in the condition of a while, do/while, f
or or if structure.)
s An example
cout << “Enter two integers: “;
int x, y;
cin >> x >> y;
cout << “The sum of “ << x << “ and “ << y
<< “ is “ << x + y << ‘n’;

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s Another example

for (int i = 0; i <= 5; i++)
cout << i << ‘n’;

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5. Creating New Data Types in C++

struct Name {
char first[10];
char last[10];
};
s In C,
struct Name stdname;
s In C++,
Name stdname;
s The same is true for enums and unions
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6. Reference Parameters

s In C, all function calls are call by value.
– Call be reference is simulated using pointers

s Reference parameters allows function arguments
to be changed without using return or pointers.

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6.1 Comparing Call by Value, Call by Reference
with Pointers and Call by Reference with References


int sqrByValue(int);
void sqrByPointer(int *);
void sqrByRef(int &);

main()
{
int x = 2, y = 3, z = 4;

cout << "x = " << x << " before sqrByValn"
<< "Value returned by sqrByVal: "
<< sqrByVal(x)
<< "nx = " << x << " after sqrByValnn";
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cout << "y = " << y << " before sqrByPointern";
sqrByPointer(&y);
cout << "y = " << y << " after sqrByPointernn";

cout << "z = " << z << " before sqrByRefn";
sqrByRef(z);
cout << "z = " << z << " after sqrByRefn";

return 0;
}

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int sqrByValue(int a)
{
return a *= a;
// caller's argument not modified
}

void sqrByPointer(int *bPtr)
{
*bPtr *= *bPtr;
// caller's argument modified
}

void sqrByRef(int &cRef)
{
cRef *= cRef;
// caller's argument modified
}

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Output

$ g++ -Wall -o square square.cc

$ square
x = 2 before sqrByValue
Value returned by sqrByValue: 4
x = 2 after sqrByValue

y = 3 before sqrByPointer
y = 9 after sqrByPointer

z = 4 before sqrByRef
z = 16 after sqrByRef
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7. The Const Qualifier

s Used to declare “constant variables” (instead of
#define)
const float PI = 3.14156;

s The const variables must be initialized when
declared.

16

8. Default Arguments

s When a default argument is omitted in a function
call, the default value of that argument is automati
cally passed in the call.
s Default arguments must be the rightmost (trailing)
arguments.

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8.1 An Example

// Using default arguments

// Calculate the volume of a box
int boxVolume(int length = 1, int width = 1,
int height = 1)
{ return length * width * height; }

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main()
{
cout << "The default box volume is: "
<< boxVolume()
<< "nnThe volume of a box with length 10,n"
<< "width 1 and height 1 is: "
<< boxVolume(10)
<< boxVolume(10, 5)
<< boxVolume(10, 5, 2)
<< 'n';

return 0;
}
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Output
$ g++ -Wall -o volume volume.cc

$ volume
The default box volume is: 1

The volume of a box with length 10,
width 1 and height 1 is: 10

width 5 and height 1 is: 50

width 5 and height 2 is: 100 20

9. Function Overloading

s In C++, several functions of the same name can be
defined as long as these function name different
sets of parameters (different types or different nu
mber of parameters).

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9.1 An Example
// Using overloaded functions

int square(int x) { return x * x; }

double square(double y) { return y * y; }

main()
{
cout << "The square of integer 7 is "
<< square(7)
<< "nThe square of double 7.5 is "
<< square(7.5) << 'n';
return 0;
}
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Output

$ g++ -Wall -o overload overload.cc

$ overload
The square of integer 7 is 49
The square of double 7.5 is 56.25

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