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25/09/2014

Course outline
Introduction to programming in C++: Keywords, identifiers, operators
(pre & post increment & decrement operators);
variables, objects and declarations; Data types;
Control structures; Pointers and references; arrays;
Functions (definition, declaration and calls);
Object-Oriented Programming (Classes, Objects, Inheritance,
Polymorphism)
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05-10
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30-2
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E
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the name of a person and his/her monthly salary belong to
different categories of data or data types
...
In practice, there may be the need to vary the
sequences and/or repeat the statements in order select from a variety of
circumstances
...
g
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 Data processing statements: Every program should be able to process data
...
E
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the statements
needed to process a person's name is different from that needed for his age
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Introduction to C++

Explanation

C++ pronounced see-plus-plus is the object oriented extension of the C programming
language
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• #include 
 The #include line is a preprocessor directive to the compiler to make
available to the following program unit what is defined in the

e
...
iostream
...
Preprocessor directives are interpreted by
the processor before the program is compiled
...

 The input/output stream header  must be included for any
program that outputs data to the screen or inputs data from the keyboard
using C++’s stream output/input
...
It is made available by the inclusion of iostream in the
complete program
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 The purpose of a namespace is to localise the names of identifiers to
avoid name collision
...

 E
...
the name cout which is brought into the program by the
preprocessor directive #include is made visible
by using namespace std; without which the stmt;
cout << " Welcome to see-plus-plus \n";
would have been; std::cout << " Welcome to seeplus-plus \n";

6

• int main()
 This marks the start of the program itself
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There may be several functions in a C++ program, but they will
always start execution at the main() function
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• The left brace, {, indicates the start of the main() function’s body
and the corresponding right brace }indicates the end of the body
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• Output statement
cout << " Welcome to see-plus-plus \n";
The above statement instructs the computer to print the string of characters
contained between the double quotation marks to the screen
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cout stands for console output
...
It prompts the
system to move the cursor to the beginning of the next line on the console
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• The return(0); indicates that the end of the main function is reached
and therefore terminates the program or exits the function and return control
to the operating system
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• A semicolon is required at the end of all C++ statements, its exclusion will
result to a syntax error
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Comments are ignored by the
C++ compiler when the program is run
...
e
...

 Comments that begin with // are called single-line comments
because they terminate at the end of the current line
...
This is a c++ style
comment
...
This is a C style comment
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9

10

• String manipulation/String data type
In c++ access to the string data type is provide in the
include file
...
these
include, determining the length of strings, characters/strings can be
inserted or deleted from existing strings, two or more string literals
can be concatenated, among others
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• Statements
 The actual C++ program resides in the statements
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 All statements are terminated by a semicolon character ‘;’
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g
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 A sequence of statements within braces ‘{’, ‘}’ is a block
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string

Constructor
...
Assign with string s =“word”

int s
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A sequence of characters between double quotation marks is simply
referred to as a string, character string, or string literal in C++
...
g
...

White-space characters in strings are not ignored by the compiler
...


string s
...

s
...


int s
...


s
...

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(2)
#include
#include
using namespace std;
int main() {
string s="My name is Floro ";
string s1="and this is Sam, my buddy ";
string s2="in the Lord of the Rings";
cout <cout << s
...
length()<<" "< ...
insert(17,s1);
return 0;
}
The statement, cout<s2 and output the final string on the screen
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The next output statement; cout << s
...
length()<<" "< ...
nb white-spaced
characters are not ignored
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insert(17,s1); inserts string
s1 at the end of string s, which has 17 characters
...
cout << s
...
 cout << s+s1
...
 cout << s
...

15

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• Variables, objects and their declarations
A variable is a symbol that represents a storage location in the computer’s
memory
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The following example declares a double variable and assigns 45
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(4)
#include
using namespace std;
int main(){
double x; //variable declaration
x=45
...
45
Besides declaring variables and later assigning values to them, they can be initialize as they are
declared
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(5)
#include
/*declaring var
...
and initializing
them*/
using namespace std;
int main(){
double x; //variable declaration
x=45
...
40; //declaring and initializing
double sum=x+y; //declaring and initializing with expression
cout <return 0;
}
The output is 45
...
45+20
...
85
17

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• Keywords and identifiers
Every program is comprised of individual syntactic elements called tokens
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Reserved words are words that are kept by the language for special purposes
and cannot be redefined for use as variables or any other purpose
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E
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int, double, char
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 Identifiers
A variable name (such as x, y, number1) is any valid identifier that is not a
keyword
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C++ is case sensitive, so a1 and A1 are different identifiers
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The syntax of
the input stream is cin>>val1>>val2>>…>>valn;
Below is a modified version of example 5 above that allows the user to input the values of x
and y from the keyboard at runtime
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using namespace std;
int main(){
double x; //variable declaration
double y; //declaring and initializing
cout<<“Enter the values of x and y: ”;
cin>>x>>y;
double sum=x+y; //computes the sum of x and y
cout <return 0;
}
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The program in example 6 above reads in more than one input using the
same cin stream
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(7)
#include
//this demonstrates how the cin object is used
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g
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Any fractional part in integer division
is discarded or truncated (i
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no rounding occurs)
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This
operator can only be used with integer operands
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Expressions in C++ must be entered in straight-line form
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g
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precedence of arithmetic operators
Operator(s) Operations

Order of evaluation

()

Parentheses

Evaluated first
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If there are several, they’re evaluated from left to right
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Arithmetic operators are some of the
simplest operators in C++
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Arithmetic operators are binary operators, i
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, operators that take two operands
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g
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These operators are summarised below:
C++ operation

C++ arithmetic operator

C++ expression

Addition

+

f+8

Subtraction

-

p-c

Multiplication

*

b*m

Division

/

x/y

Modulus

%

r%s

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(8) #include
//this demonstrates the use of arithmetic operators
using namespace std;
int main(){
int m=13, n=10;
cout<cout<cout<cout<cout<return 0;
}

Evaluated last
...

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• Compound Asignment Operators
 C++ provides several assignment operators for abbreviating assignment expressions
...
g
...
*=, -=, /=, and %= are all compound assignment
operators
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--

Preincrement

Decrement b by 1, then use the new value of b in the
expression in which b resides

--

Postincrement b--

--b

Use the current value of b in the expression in which b resides,
then decrement b by 1
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• Equality and Relational operators
Standard algebraic C++ equality Sample C++
equality or
or relational condition
relational operator operator

Meaning of C++ condition

Relational operators
>

>

x>y

x is greater than y

<

<

x
x is less than y

≥

>=

x>=y

x is greater than or equal to y

≤

cout<
<=

x<=y

x is less than or equal to y

Equality operators

//demonstrate preincrement
c=5; //assign 5 to c
cout<cout<<++c<cout<}

• Increment and Decrement operators
In addition to the assignment operators, C++ also provides two unary operators
for adding 1 to or subtracting 1 from the value of a numeric variable
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These operators are summarised below
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in some cases, writing != as =! will not be a syntax error but most definitely will
be a logical error that has an effect at execution time
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• Control Structures/statements
Normally, statements in a C++ program execute one after the other in the order
in which they are written
...

All that we have learnt so far, each statement executes once, in a sequence or
the other in which they appear in the program
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(11) #include
using namespace std;
/*this program prints “Passed” if student score is
greater than or equal to 60 */
int main(){
int grade;
cout <<“Enter student’s grade : “;
cin>>grade;
if(grade>=60)
cout<<“Passed”;
}
This program used the if statement to evaluate the exams score of a student and
prints Passed if the score is greater than or equal to 60 or exits if false
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These include the conditional/ selection statements and repetition
statements
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• The if statement
The if selection statement is a single-selection statement that allows conditional
execution by either selecting or ignoring a single action or a single group of
actions
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• The program below compare two numbers using six if statements
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(12) #include
using namespace std;
int main(){
int number1, number2;
cout <<“Enter two integers to compare: “;
cin>>number1>>number2;
if(number1==number2)
cout<if(number1!=number2)
cout<
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if(number1cout<if(number1<=number2)
cout<if(number1>number2)
cout<”<if(number1>=number2)
cout<=”<}
Number1=3, number2=7

Number1=22, number2=12

3!=7

22!=12

3<7

22>12

3<=7

Output

22>=12
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The above program outputs “Passed” if grade is greater than or equal to 60 and
Failed otherwise
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It takes three operands, the operands together with the condition operator, form a
conditional expression
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E
...
the output statement
cout<<(grade>=60 ? “Passed” : “Failed);
contain a condition statement , (grade>=60 ? “Passed” : “Failed);
that evaluates to “Passed” if the condition grade>=60 is true and to “False” if
false
...
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• The if … else selection statement
The if … else statement is called a double-selection statement because it selects
between two different actions (or group of actions) depending upon the value of a
condition (i
...
it performs on action if the condition is true and the other if the
condition if false)
...
Compound
statements in C++ are enclosed in curly braces
...
g
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The following program uses compound statements to sort two integers in
increasing order

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Title: C++ NOTES
Description: This note is made of the basics in C++

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