c++ Chapter 2.pptfdffffffffffffffgffffgggfffx

Chapter two
C++ Programming Basics

Introduction to C++ Program
 C++ is a 3rd-generation language used for creating computer programs.
 These types of languages must be translated into a machine language in order to
be executed by a CPU.
 The process of translating high-level language into machine language is called the
compilation process.
The compilation process consists of the following steps.
• edit source code -> compile -> link -> execute
(editor) (compiler) (linker) (loader)
 Program source code is entered into a file using a text editor.
 After the code has been entered, a compiler program is started that translates the source
into an object code file.
 The object code file is linked with other object code files that come with the compiler and
an executable file (or program) is created.
 In order to execute the program, the loader copies the executable file into the memory of
the computer and sends an execute command to the CPU.

The Steps to Create an Executable File

C++ IDE(Integrated Development Environment)
IDE is the software that helps the programmer to write your code. Example
Code::Blocks and Dev-C++
 The complete development cycle in C++ is: Write the program, compile the
source code, link the program, and run it.
Write the program
• To write a source code, your compiler may have its own built-in text editor, or
you may be using a commercial text editor.
• The files you create with your editor are called source files, with a .CPP
extension.
Compiling
• Your source code file can't be executed, or run, as a program can.
• To turn your source code into a program, you use a compiler.
• After your source code is compiled, an object file is produced with the
extension .OBJ.
• This is still not an executable program, however, to turn this into an
executable program, you must run your linker.

Cont….
Linking
• C++ programs are typically created by linking together one or more OBJ files
with one or more libraries and generate an executable file.
• In order to execute the program, the loader copies the executable file into the
memory of the computer and sends an execute command to the CPU.
The steps to create an executable file are :
1. Create a source code file, with a .CPP extension.
2. Compile the source code into a file with the .OBJ extension.
3. Link your OBJ file with any needed libraries to produce an executable
program.

Structure of a C++ program includes:

Cont.….
• Documentation Section: include comment parts, which is ignored by
compiler.
• The comments are used to describe the functionality of each statement in the
program to the user.
• Link section: here we can link the necessary files and libraries to current files.
– Using #include directive we can link the necessary libraries to current
files.
Syntax: #include<file or library name>
Example: #include<iostream.h>
• Definition Section: It is possible to define symbolic constants. Symbolic
constants are normal identifiers which value cannot be altered/modified.
Syntax: #define identifier constant
• Global declaration Section: variables declared under this section are
available throughout the program.
• Class declaration Section: defines the class declaration.

Cont.….
• Functions: function is block of instruction that is executed when it is called
form some other point of a program.
Syntax:
return type function name (){
Statement of function; }
– A function is identified by the compiler with the help of parenthesis ( )
after the function name.
– The statement inside the brace {} forms the body of the function and
specifies the task of the function.
– Return type specifies the type of data the function has to send to the
calling function after the execution.
• main ( ) function: the execution of the program starts from main function.
• Every program must have only one main function. The initialization or other
executable statements are included with in the main function.
• Every statement under global declaration, initialization and executable parts
should be terminated with the semi colon (;). A semi colon acts as a statement
terminator like full stop in English.

C++ Sample program
For example
//C++ sample program
#include <iostream.h>
int main()
{
cout << "Hello World!n";
}
• Any C++ program file should be saved with file name extension “ .CPP ”.
• Type the program directly into the editor, and save the file as hello.cpp, compile
it and then run it.
• It will print the words Hello World! on the computer screen.
• The return value type for main() here is int, which means main function will
return a value to the caller.
• cout is an object used for printing data to the screen.
• Every single statement ends with semicolon (;).

cout and cin Statements
cout is an object used for printing data to the screen.
• To print a value to the screen, write the word cout, followed by the insertion operator
also called output redirection operator (<<) and the object to be printed on the screen.
• Syntax: cout<<Object;
The object at the right hand side can be:
– A literal string: “Hello World”
– A variable: a place holder in memory
 cin is an object used for taking or accepting an input value from the keyboard.
• To take input from the keyboard, write the word cin, followed by the input redirection
operator (>>) and the object name to hold the input value.
 Syntax: cin>>Object
 cin will take value from the keyboard and store it in the memory.
 Both << and >> return their right operand.
 multiple input or multiple output operations can be combined into one statement.
Example
 cin>>var1>>var2>>var3; // three different values will be entered for the three variables
 cout<<var1<<var2<<var3;// the values of the three variables will be printed

C++ Basic Elements
1 Keywords (reserved words)
• Reserved/Key words have a unique meaning within a C++ program. These
reserved words, must not be used for any other purposes.
• All reserved words are in lower-case letters.
Asm auto bool break case catch
const_cast class const char continue default
dynamic_cast do double delete else enum
Explicit extern false float for friend
Goto if inline int long mutable
Namespace new operator private protected public
reinterpret_cast register return short signed sizeof
static_cast static struct switch template this
Throw true try typedef typeid typename
Union unsigned using virtual void volatile
wchar_t

C++ Basic Elements
2 Identifiers
An identifier is name associated with a function, variable, array, structure or
class. An identifier must:
• Start with a letter or underscore( _ )
• Consist only of letters, the digits 0-9, or the underscore symbol _
• Not be a reserved word
Note: C++ is case sensitive
The following are valid identifiers
The following are invalid:
Length days_in_year DataSet1 Profit95
Int _Pressure first_one first_1
days-in-year 1data int first.val
throw My…best No## bestWish!

C++ Basic Elements
3 Constants
 A constant is any expression that has a fixed value.
 C++ provides two types of constants: Literal and Symbolic constants.
 Literal Constant is a constant value which can be a number, a character of a
string, typed directly into the program wherever it is needed.
e.g cout<<50; //50 is a literal constant in this statement
• There is no identifier that identifies them. Ex. Cout<<“Hello world”;
 Symbolic constant: is a constant value that is represented by a name,
simlar to that of a variable . In C++ , There are two ways to declare a
symbolic constant.
• using #define and const keyword.
E.g. #define PI 3.14 or const float PI=3.14;

C++ Basic Elements
4 Comments
• A comment is a piece of descriptive text which explains some aspect of a
program.
• Program comments are text totally ignored by the compiler and are only
intended to inform the reader.
C++ provides two types of comment delimiters:
 Single Line Comment: Anything after // {double forward slash} (until the
end of the line on which it appears) is considered a comment.
– Eg:
cout<<var1; //this line prints the value of var1
 Multiple Line Comment: Anything enclosed by the pair /* and */ is
considered a comment.
– Eg:
/*this is a kind of comment where
Multiple lines can be enclosed in
one C++ program */

Data Types and Variables in C++
Variables
• A variable is a reserved place or a symbolic name in memory location to store
information.
• Variables are used for holding data values
All variables have two important attributes:
– Data Type: a type which is established when the variable is defined. (e.g.
integer, float, character etc.).
• It describes the property of the data or variable value and the size of the
reserved memory.
– Value: a value which can be changed by assigning a new value to the variable.
 Variable Declaration
 Declaring a variable means defining (creating) a variable.
 Create or define a variable by stating its type, followed by one or more spaces,
followed by the variable name and a semicolon.
 Syntax: Datatype Variable_Name;
E.g. int myAge; //variable used to store my age

Cont.….
 Creating/declaring more than One Variable at a Time
 You can create more than one variable of the same type in one statement by
writing the type and then the variable names, separated by commas.
 For example:
int myAge, myWeight; // two int variables
long area, width, length; // three longs
 Assigning Values to Your Variables
 assign a value to a variable by using the assignment operator (=).
Example
int Width; Width = 5;
int Width = 5;
 you can define more than one variable at a time, you can initialize more than
one variable at creation. For example:
// create two int variables and initialize them
int width = 5, length = 7;

Basic Data Types
 Data type describes the property of the data and the size of the reserved
memory
 It can be conveniently divided into numeric and character types.
• Numeric variables can further be divided into integer variables and floating-
point variables.
• Integer variables will hold only integers whereas floating number variables
can accommodate real numbers.
Type Length Range
char 8 bits 0 to 255
unsigned int 16 bits 0 to 65,535
short int 16 bits -32,768 to 32,767
int 16 bits -32,768 to 32,767
unsigned long 32 bits 0 to 4,294,967,295
long 32 bits -2,147,483,648 to 2,147,483,647
Float 32 bits -3.4x10-38
to 3.4x10+38
double 64 bits -1.7x10-308
to 1.7x10+308
long double 80 bits -3.4x10-4932
to 1.1x10+4932
bool 8 bits true or false

Cont.….
Signed and Unsigned data types
 signed integers are either negative or positive. Unsigned integers are always positive.
 An unsigned short integer can handle numbers from 0 to 65,535.
 a signed short can only represent numbers from -32,768 to 32,767.
 The largest number you can store in an unsigned integer is twice as big as the largest
positive number you can store in a signed integer.
Example: A demonstration of the use of variables.
#include <iostream.h>
int main()
{
unsigned short int Width = 5, Length;
Length = 10;
unsigned short int Area = Width * Length;
cout << "Width:" << Width << "n";
cout << "Length: " << Length << endl;
cout << "Area: " << Area << endl;
return 0;
}

Cont.….
Signed and Unsigned data types
 When an unsigned integer reaches its maximum value the result counter back to 0.
Example: A demonstration of putting too large a value in a variable
1: #include <iostream.h>
2: int main()
3: {
4: unsigned short int smallNumber;
5: smallNumber = 65535;
6: cout << "small number:" << smallNumber << endl;
7: smallNumber++;
9: smallNumber++;
11: return 0;
12: }
Output:
small number:65535
small number:0
small number:1

Cont.….
Characters
 Character variables (type char) are typically 1 byte, enough to hold 256
values.
 A char can be interpreted as a small number (0-255) or as a member of the
ASCII set.
 The ASCII character set is a way to encode all the letters, numerals, and
punctuation marks.
 E.g In the ASCII code, the lowercase letter "a" is assigned the value 97 and the
Uppercase letter “A" is assigned the value 65.
 All the lower- and uppercase letters, all the numerals, and all the punctuation
marks are assigned values between 0 and 127. Another 128 marks and symbols
are reserved for use by the computer maker.

Cont.….
Operators
Operator is a symbol that makes the machine to take an action.
 C++ provides operators for composing arithmetic, relational, logical, bitwise,
and conditional expressions.
Assignment Operators
The assignment operator(=) is used for storing a value at some memory location
(typically denoted by a variable). Syntax: operand1=operand2
Operator Example Equivalent To
= n = 25
+= n += 25 n = n + 25
-= n -= 25 n = n - 25
*= n *= 25 n = n * 25
/= n /= 25 n = n / 25
%= n %= 25 n = n % 25
&= n &= 0xF2F2 n = n & 0xF2F2

Cont.….
Arithmetic Operators
C++ provides five basic arithmetic operators.
 Except for remainder (%) all other arithmetic operators can accept a mix of
integer and real operands.
 remainder (%) gives the reminder of a division of two integer values.
 Generally, if both operands are integers then the result will be an integer.
However, if one or both of the operands are reals then the result will be a real
(or double to be exact).
Operator Name Example
+ Addition 12 + 4.9 // gives 16.9
- Subtraction
3.98 - 4 // gives -0.02
* Multiplication 2 * 3.4 // gives 6.8
/ Division 9 / 2.0 // gives 4.5
% Remainder 13 % 3 //gives 1
// gives 1
Arithmetic operators.

Cont.….
 Integer division always results in an integer outcome (i.e., the result is always
rounded down). Example
• 9 / 2 // gives 4, not 4.5!
• -9 / 2 // gives -5, not -4.5!
 There are also a number of predefined library functions, which perform
arithmetic operations.
Header File Functio
n
Parameter
Type(s)
Result Type
Result
<stdlib.h> abs(i) int int Absolute value of i
<math.h> cos(x) float float Cosine of x (x is in
radians)
<math.h> fabs(x) float float Absolute value of x
<math.h> pow(x, y) float float x raised to the power
of y
<math.h> sin(x) float float Sine of x (x is in
radians)
<math.h> sqrt(x) float float Square root of x
<math.h> tan(x) float float Tangent of x

Cont.….
Relational Operators
 C++ provides six relational operators for comparing numeric quantities or to
evaluate a comparison between two or more expressions. The result of a
relational operator is a bool value that can only be true(1) or false (0)
according to the result of the comparison.
• The operands of a relational operator must evaluate to a number.
• Characters also valid operands since they are represented by numeric values,
but should not be used for comparing strings.
• For example (assuming ASCII coding):
'A' < 'F’ // gives 1 (is like 65 < 70)
== Equality 5 == 5 // gives 1
!= Inequality 5 != 5 // gives 0
< Less Than 5 < 5.5 // gives 1
<= Less Than or Equal 5 <= 5 // gives 1
> Greater Than 5 > 5.5 // gives 0
>= Greater Than or Equal 6.3 >= 5 // gives 1
Relational operators

Cont.….
Logical Operators
C++ provides three logical operators for combining logical expression. Like the
relational operators, logical operators evaluate to 1(True) or 0(false).
Logical negation is a unary operator, which negates the logical value of its single
operand. If its operand is nonzero it produces 0, and if it is 0 it produces 1.
Logical and produces 0 if one or both of its operands evaluate to 0. Otherwise, it
produces 1.
Logical or produces 0 if both of its operands evaluate to 0. Otherwise, it produces 1.
• In general, any nonzero value can be used to represent the logical true, whereas
only zero represents the logical false.
! Logical
Negation
!(5 == 5) // gives 0
&& Logical And 5 < 6 && 6 < 6 // gives 1
|| Logical Or 5 < 6 || 6 < 5 // gives 1
Logical operators

Cont.….
Conditional Operators (?)
• The conditional operator evaluates an expression and
returns a different value according to the evaluated
expression, depending on if its true or false,
Syntax: (condition? result1 :result2)
• If condition is true the expression will return result1, if
not it will return result2.
• Example:( 7==5? 4:3) // returns 3 since 7 is not equal
to 5.
• (7==5+2? 4:3) //returns 4 since 7 is equal to 5+2.
• (5>3 ? a:b) //returns a since 5 is greater than 3.
cout<<(7==5?4:6); // returns 6

Cont.….
Bitwise Operators
 Perform operations on integer data at the individual bit-level.
 C++ provides six bitwise operators for manipulating the individual bits in an
integer quantity.
~ Bitwise Negation ~'011' // gives '366'
& Bitwise And '011' & '027' // gives '001'
| Bitwise Or '011' | '027' // gives '037'
^ Bitwise Exclusive
Or
'011' ^ '027' // gives '036'
<< Bitwise Left Shift '011' << 2 // gives '044'
>> Bitwise Right
Shift
'011' >> 2 // gives '002'
Bitwise operators

Cont.….
Bitwise Operators
Bitwise operators expect their operands to be integer quantities and treat them as
bit sequences.
 Bitwise negation is a unary operator which reverses the bits in its operands.
 Bitwise and compares the corresponding bits of its operands and produces a 1
when both bits are 1, and 0 otherwise.
 Bitwise or compares the corresponding bits of its operands and produces a 0
when both bits are 0, and 1 otherwise.
 Bitwise exclusive or compares the corresponding bits of its operands and
produces a 0 when both bits are 1 or both bits are 0, and 1 otherwise.
 Bitwise left shift operator(<<) produces a bit sequence equal to the left
operand but which has been shifted n bit positions to the left. Vacated bits at
either end are set to 0
 Bitwise right shift operator (>>) produces a bit sequence equal to the left
operand but which has been shifted n bit positions to the right. Vacated bits at
either end are set to 0.

Cont.….
Example:
unsigned char x = '011’; 9
unsigned char y = '027’; 23
Example Octal Value Bit Sequence
X 011 0 0 0 0 1 0 0 1
Y 027 0 0 0 1 0 1 1 1
~x 366 1 1 1 1 0 1 1 0
x & y 001 0 0 0 0 0 0 0 1
x | y 037 0 0 0 1 1 1 1 1
x ^ y 036 0 0 0 1 1 1 1 0
x << 2 044 0 0 1 0 0 1 0 0
x >> 2 002 0 0 0 0 0 0 1 0

Increment/decrement Operators
 The auto increment (++) and auto decrement (--) operators provide a
convenient way of, adding and subtracting 1 from a numeric variable
respectively.
int k = 5;
Both operators can be used in prefix and postfix form.
• When used in prefix form, the operator is first applied and the outcome is then
used in the expression.
• When used in the postfix form, the expression is evaluated first and then the
operator applied.
++ Auto Increment (prefix) ++k + 10 // gives 16
++ Auto Increment (postfix) k++ + 10 // gives 15
-- Auto Decrement (prefix) --k + 10 // gives 14
-- Auto Decrement (postfix) k-- + 10 // gives 15
Increment and decrement operators

Precedence of Operators
• The order in which operators are evaluated in an expression is significant and
is determined by precedence rules.
• These rules divide the C++ operators into a number of precedence levels.
For example
a =b + c * d
• c * d is evaluated first because * has a higher precedence than + and =. The
result is then added to b because + has a higher precedence than =, and then =
is evaluated.
a = (b + c) * d

Simple Type Conversion
• A value in any of the built-in types can be converted (type-cast) to any of the
other types. For example:
(int) 3.14 // converts 3.14 to an int to give 3
(long) 3.14 // converts 3.14 to a long to give 3L
(double) 2 // converts 2 to a double to give 2.0
(char) 122 // converts 122 to a char whose code is 122
(unsigned short) 3.14 // gives 3 as an unsigned short
Explicit type conversion: are unary (i.e., take one operand) and appear inside
brackets to the left of their operand.
E.g int (3.14) // same as: (int) 3.14
Implicit type conversion: This happens when values of different types are mixed
in an expression.
e.g double d = 1; // d receives 1.0
int i = 10.5; // i receives 10
i = i + d; // means: i = int(double(i) + d)

Statements
Statements represent the lowest-level building blocks of a program. C++ provides
different forms of statements for different purposes.
 Declaration statements are used for defining variables.
 Assignment-like statements are used for simple, algebraic computations.
 Loop statements are used for specifying computations which need to be
repeated until a certain logical condition is satisfied.
 Flow control statements are used to divert the execution path to another part
of the program.

The block statement
• A block begins with an opening brace ({) and ends with a closing brace (}).
• Every statement in the block must end with a semicolon, the block itself does
not end with a semicolon.
Syntax:
{
[<Declarations>].
<List of statements/statement block>.
}
The Assignment statement(=)
Syntax:
<Variable Identifier> = < expression>;
• The <expression> is evaluated and the resulting value is stored in the memory space
reserved for <variable identifier>.
Eg: - int x,y ;
x=5;
y=x+3;
x=y*y;

Prepared By: Getie B.
End of chapter two
Questions???

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