HNDE Lecture note..Labuduwa Galle.. upload by sika

1. Information Technology
III
Introduction to Programming with C++

2. History of C and C++
 History of C++
 Extension of C
 Early 1980s: Bjarne Stroustrup (Bell Laboratories)
 Provides capabilities for object-oriented programming
Objects: reusable software components
Model items in real world
Object-oriented programs
Easy to understand, correct and modify
 Hybrid language
C-like style
Object-oriented style
Both
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3. Basics of a Typical C++ Environment
 C++ systems
 Program-development environment
 Language
 C++ Standard Library
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4. Basics of a Typical C++ Environment4
Phases of C++ Programs:
1. Edit
2. Preprocess
3. Compile
4. Link
5. Load
6. Execute
Loader
Primary
Memory
Program is created in
the editor and stored
on disk.
Preprocessor program
processes the code.
Loader puts program
in memory.
CPU takes each
instruction and
executes it, possibly
storing new data
values as the program
executes.
Compiler
Compiler creates
object code and stores
it on disk.
Linker links the object
code with the libraries,
creates a.out and
stores it on disk
Editor
Preprocessor
Linker
CPU
Primary
Memory
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Disk
Disk
Disk
Disk
Disk

5. Hello World
This is a comment line - the line
is a brief description of program
does.
directives for the preprocessor.
They are not executable code
lines but indications for the
compiler.
<iostream.h> tells the compiler's
preprocessor to include the iostream
standard header file.
cout is the standard
output stream
The return instruction causes the main()
function finish and return the code terminating
the program without any errors during its
execution
This line corresponds to the beginning
of the main function declaration. The
main function is the point C++
programs begin their execution. It is
first to be executed when a program
starts.

6. Basics of a Typical C++ Environment
 Input/output
 cin
Standard input stream
Normally keyboard
 cout
Standard output stream
Normally computer screen
 cerr
Standard error stream
Display error messages
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7. Comments
 It is of 2 types:-
 Single line comments //
 example of single line comment
//this is the very simple example of single line comments
 Multi line comments
/*
This is the example of
multi line comment
*/

8. A Simple Program: Printing a Line of
Text
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Escape Sequence Description
n Newline. Position the screen cursor to the
beginning of the next line.
t Horizontal tab. Move the screen cursor to the next
tab stop.
r Carriage return. Position the screen cursor to the
beginning of the current line; do not advance to the
next line.
a Alert. Sound the system bell.
Backslash. Used to print a backslash character.
" Double quote. Used to print a double quote
character.

9. Variables
 Variable names
Valid identifier
Series of characters (letters, digits, underscores)
Cannot begin with digit
Case sensitive
length of an identifier is not limited, (but some compilers
only the 32 first characters rest ignore)
Neither spaces nor marked letters can be part of an
identifier
can also begin with an underline character ( _ )
your own identifiers cannot match any key word of the C++
language
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10. Variables
 Location in memory where value can be stored
 Common data types
int - integer numbers
char - characters
double - double precision floating point numbers
Float - floating point numbers
Bool - Boolean value (true or false)
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11. Signed and Unsigned Integer Types
 For integer data types, there are three sizes:
 Int
 long - larger size of integer,
 short, which are declared as long int and short int.
 The keywords long and short are called sub-type qualifiers.
 The requirement is that short and int must be at least 16 bits, long must be at
least 32 bits,
 short is no longer than int, which is no longer than long.
 Typically, short is 16 bits, long is 32 bits, and int is either 16 or 32 bits.
 all integer data types are signed data types,
 i.e. they have values which can be positive or negative

12. Declaration of variables
 Declare variables with name and data type before use
int a;
float mynumber;
int MyAccountBalance;
int integer1;
int integer2;
int sum;
int integer1, integer2, sum;

13. Example
 A program to add two numbers;
#include<iostream>
using namespace std;
int main() {
int a, b; // variable declaration
a = 10;
b= 20;
int addition = a + b;
cout << “answer is:” << addition << endl;
return 0;
}

14. Scope of variables
Global variables can
be referred to
anywhere in the
code, within any
function, whenever it
is after its declaration.
The scope of the local
variables is limited
to the code level in
which they are
declared.

15. Constants: Literals
 A constant is any expression that has a fixed value.
 It can be Integer Numbers, Floating-Point Numbers, Characters and
Strings
 Examples
 75 // decimal
 0113 // octal
 0x4b // hexadecimal
 6.02e23 // 6.02 x 10 23
 1.6e-19 // 1.6 x 10 -19
 3.0 // 3.0
 #define PI 3.14159265
 #define NEWLINE 'n'
circle = 2 * PI * r;
cout << NEWLINE;

16. Defined constants (#define)
 You can define your own names for constants simply by using the
#define preprocessor directive.
 #define identifier value
 Example
 #define PI 3.14159265
 #define NEWLINE 'n'
 #define WIDTH 100

17. Operators
 Input stream object
 >> (stream extraction operator)
Used with std::cin
Waits for user to input value, then press Enter (Return) key
Stores value in variable to right of operator
Converts value to variable data type
 = (assignment operator)
 Assigns value to variable
 Binary operator (two operands)
 Example:
sum = variable1 + variable2;
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18. Arithmetic operators
 The five arithmetical operations
+ addition
- subtraction
* multiplication
/ division
% module

19. Example
int a, b;
a = 10;
b = 4;
a = b;
b = 7;
a = 2 + (b = 5);
a = b = c = 5;
a -= 5;
a /= b;
a++;
a+=1;
a=a+1;
B=3;
A=++B;
A=B++;

20. Relational operators
 == Equal
 != Different
 > Greater than
 < Less than
 >= Greater or equal than
 <= Less or equal than
 (7 == 5)
 (5 > 4)
 (3 != 2)
 (6 >= 6)
 Suppose that a=2, b=3and
c=6,
 (a == 5)
 (a*b >= c)
 (b+4 > a*c)
 ((b=2) == a)

21. Logic operators ( !, &&, || )
 For example:
 ( (5 == 5) && (3 > 6) )
 ( (5 == 5) || (3 > 6))
 Conditional operator ( ? )
 condition ? result1 : result2
 if condition is true the expression will return result1, if not it
will return result2.
 7==5 ? 4 : 3
 7==5+2 ? 4 : 3
 5>3 ? a : b

22. Precedence of Operators
 Rules of operator precedence
 Operators in parentheses evaluated first
 Nested/embedded parentheses
 Operators in innermost pair first
 Multiplication, division, modulus applied next
 Operators applied from left to right
 Addition, subtraction applied last
 Operators applied from left to right
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Operator(s) Operation(s) Order of evaluation (precedence)
() Parentheses Evaluated first. If the parentheses are nested, the
expression in the innermost pair is evaluated first. If
there are several pairs of parentheses “on the same level”
(i.e., not nested), they are evaluated left to right.
*, /, or % Multiplication Division
Modulus
Evaluated second. If there are several, they re
evaluated left to right.
+ or - Addition
Subtraction
Evaluated last. If there are several, they are
evaluated left to right.

23. Types of Errors
 Syntax errors
A syntax error occurs when the programmer fails to obey one of the grammar
rules of the language.
 Runtime errors
A runtime error occurs whenever the program instructs the computer to do
something that it is either incapable or unwilling to do.
 Logic errors
Logic errors are usually the most difficult kind of errors to find and fix, because
there frequently is no obvious indication of the error.
Usually the program runs successfully. It simply doesn't behave as it should.
it doesn't produce the correct answers.

24. Syntax errors
Syntax Error: undeclared identifer “cout”

25. Syntax errors
 result = (firstVal - secondVal / factor;
Syntax Error: ’)’ expected
 cout << “Execution Terminated << endl;
Syntax Error: illegal string constant
 double x = 2.0, y = 3.1415, product;
x * y = product;
Syntax Error: not an l-value

26. Logical errors
 int a, b;
int sum = a + b;
cout << "Enter two numbers to add: ";
cin >> a; cin >> b;
cout << "The sum is: " << sum;
 char done = 'Y';
while (done = 'Y') {
//... cout << "Continue? (Y/N)";
cin >> done;
}