Chapter two

C++ Programming Basics

 Structure of C++ Program

 C++ is a 3rd-generation language. 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.
 C++ IDE(Integrated Development Environment)
IDE is the software that helps you 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.
• A library is a collection of linkable files
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";
return 0;
}
• 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.
 C++ Basic Elements
2 Identifiers

An identifier is name associated with a function. 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

The following are valid identifiers

Length days_in_year DataSet1 Profit95

Int _Pressure first_one first_1

The following are invalid:

days-in-year 1data int first.val

Throw my__best No## bestWish!
 C++ Basic Elements
3 Literals
• Literals are constant values which can be a number, a character of a string.
• There is no identifier that identifies them. Ex. Cout<<“Hello world”;
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, Variables, and Constants
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 32 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 (top 7 bits are ignored)
 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++;
8: cout << "small number:" << smallNumber << endl;
9: smallNumber++;
10: cout << "small number:" << smallNumber << endl;
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
 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).

Operato Example Equivalent To

r
= 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.

Operator Name Example

+ Addition 12 + 4.9 // gives 16.9

3.98 - 4 // gives -0.02
- Subtraction

* Multiplication 2 * 3.4 // gives 6.8

/ Division 9 / 2.0 // gives 4.5

% Remainder 13 % 3 //gives 1 // gives 1

Arithmetic operators.

 Except for remainder (%) all other arithmetic operators can accept a
mix of integer and real operands.
 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).
 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!
 There are also a number of predefined library functions, which perform
arithmetic operations.
Paramete Result Type
Functio
Header File r Type(s) Result
n
<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.
Relational operators evaluate to 1 ( true ) or 0 (false).

Operator Name Example

== 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

• 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)
 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).

Operato Name Example

r
! Logical !(5 == 5) // gives 0
Negation
&& Logical And 5 < 6 && 6 < 6 // gives 1

|| Logical Or 5 < 6 || 6 < 5 // gives 1

Logical negation
Logical is a unary operator, which negates the logical value of its single
operators
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.
 Cont.….
Bitwise Operators
C++ provides six bitwise operators for manipulating the individual bits in
an integer quantity.
Operator Name Example

~ Bitwise ~'\011' // gives '\366'

Negation
& Bitwise And '\011' & '\027' // gives '\001'

| Bitwise Or '\011' | '\027' // gives '\037'

^ Bitwise '\011' ^ '\027' // gives '\036'

Exclusive Or
<< Bitwise Left '\011' << 2 // gives '\044'
Shift
>> Bitwise Right '\011' >> 2 // gives '\002'
Shift
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';
unsigned char y = '\027';

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; Operator Name Example
++ 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

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.
 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;
 t w o
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d o io n
E n e s t
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Prepared By: Getie B.