1. CHAPTER 2: COMPONENTS OF PROGRAMMING LANGUAGE
PROGRAMMING C++ DOPC 330
CHAPTER 2:
COMPONENTS OF PROGRAMMING LANGUAGE

2. Objectives To understand the basic structure of C++ program
To introduce the concepts of
Data types
Identifiers: variables & constants
To introduce input & output statement
To introduce a formatting output

3. Structure of C++ Program

4. Structure of C++ Program : Comments
Two format
Line comment
Marked by two slashes (//) at the beginning of comment
For short comment : in a single line
Example: // written by: Mohd Suffian Sulaiman
Block comment
Marked by opening token (/*) and closing token (*/)
For long comment
Example: /*This program is to calculate the area of a cylinder*/
Comments CANNOT be nested (comments inside comments)
Use: to document programs and improve program readability
Help other people read and understand others program
IGNORED by C++ compiler and DO NOT cause any machine language object code to be generated
DO NOT cause the computer to perform any action when the program is run
CAN be put ANYWHERE in the program

5. Structure of C++ Program: Preprocessor Directive
Will be read first before the program is compiled
Indicated by pound sign/hash (#) together with keyword
#include – to include the contents of another file
#define – to define global variable/ constant
**No space between # and include
#include<iostream.h>
iostream.h
Is the name of the file that is to be included
Dot h indocates the type of the file – header file
Allow C++ program to display output on the screen – cout and read input from keyboard - cin
#define pi 3.142
pi – Name of constant
3.142 – value of the constant

6. Structure of C++ Program: main function
C++ program can have one or more functions, exactly one MUST be main() function
int main()
int – stands for integer. It indicates that the function sends an integer back to operating system when it is finished executing
main() – the name of the function
MUST be followed by set of braces ({ }) – indicates a block, the beginning and ending of a function
All statements (function body) that make up a function are enclosed in a set of braces

7. Structure of C++ Program: function body
Enclosed by a set of braces ( { } )
Function contains
Local declaration
Declaration of data that will be used for the function/program
Example: float radius, height;
program body
Set of instructions of what the function/program should do
Return statement
Return value that sends back to operating system
Example: return 0; // 0 indicates the program executes successfully

8. Common Programming Language Elements
Syntax
Rules that must be followed when constructing a program
Lines / Lines of code
A ‘line’ is a single line appear in the body of program
Statement
A complete instruction that causes the computer to perform some action
Keywords (Reserve Words)
Words that have special meaning and used for intended purpose

9. Common Programming Language Elements
Programmer-Defined Identifier (Identifier)
Words/names defined by programmer. Symbolic names refer to variables or functions
Punctuations
Punctuation characters mark the beginning or ending of a statement or separate item in a list

10. Punctuations Comma ( , )  use to separate item in alist
Example:
float radius, height;
Semicolon ( ; )
Use at the end of a complete instruction
Printf(“Enter radius: ”);
Cylinder = 2*pi*radius*height;
Return 0;

11. Reserve Word / Keyword
Special words reserve for C++ program which have specific meaning and purpose
CANNOT be used as identifiers or variable name
Appear in lower case

12. Identifiers
Allows programmers to NAME data and other objects in the program
Variable, constant, function etc
Rules in naming identifiers
MUST consist ONLY of alphabetic characters (uppercase or lowercase), digits and underscores ( _ )
First character MUST be alphabetic character or underscore
CANNOT contain spaces
CANNOT dupliacte with any reserved word
**C++ is CASE SENSITIVE
This means that NUM1,Num1,num1 and NuM1 are four completely different name.

13. Example of Valid & Invalid Identifiers

14. Variables
Variable names correspond to locations in the computer’s memory
Every variable has a NAME, a DATA TYPE, a SIZE and a VALUE
A variable is created via a declaration where its name and type are specified
Example
int integer1,integer2,sum;
Whenever a new value is placed into a variable (through cin, for example), it replaces (and destroys) the prevoius value.

15. Variable Declaration
Specifies in the memory to reserve a specific space for the variable that have the specific location and can store specific data type
MUST be declared before the executable of the statement
Variable need to FIRST declare before it being used
Syntax:
data type variable name;
example:
int maxItems;
float payRate;
double tax;
char code;
int a,b;

16. Example of Variable in Memory

17. Data Types Variables are classified according to their data type
Determine the kind of information stored in variables
Address, phone numbers, price, distance and etc.
Functions also have types which determine by the data it returns
C++ program have 5 standard data types:
void
Floating point: double & float
int
char
string

18. Data Types

19. Numeric Data Type
Numeric data types rae broken into 2 categories: Integer and Floating-point
Primary consideration for selecting data types:
The largest and smallest number that maybe stored in the variable
How much memory does the variable use
Whether the variable stores signed or unsigned numbers
The number of decimal places of precision the variables has
The size of variable is the number of bytes of memory it uses. (> variable  > range can hold)

20. Integer Data Type To store WHOLE NUMBER without fraction
C++ program supports 3 different sizes of integer
short int
Int
long int

21. Floating Point Data Type
To store Floating-point number
C++ program supports 3 different sizes of numbers
Float
Double
Long double

22. Char Data Type The smallest integral data type
Memory allocated for the char type is 1 byte
Used for characters: letters, digits and special symbols
Each character is enclosed in single quotes
Some of the values belonging to char data type are: ‘A’, ‘a’, ‘0’, ‘*’, ‘$’ etc
A blank space is a character and is written ‘ ’, with a space left between the single quotes
Find the range of char datatype?

23. Char Data Type

24. String Data Type Programmer-defined type supplied in standard library
Sequence of zero or more characters
Enclosed in double quotation marks
Null: a string with no characters
Each character has relative position in string
Position of first character is 0, the position of the second is 1, and so on
Length: number of characters in string

25. String Data Types

26. Variable Initialization
To establish the first value that the variable will contain
Syntax:
data_type variable_name = value;
Example:
int count =5;
int sum=0;
char letter = ‘a’;
float price = 45.99;

27. Constants
To define values that CANNOT be changed during the execution of a program
Types of constant: integer constant, float constant, character constant, string constant and symbolic constant
3 ways of defining a constant
Literal constant
Defined constant – using pre-processor
Defined constant – using const

28. Literal Constant An unnamed constant used to specify data
If the data CANNOT be changed, it can simply code the value itself in a statement
Example;
‘A’ 5
A + 5
3.1455
“Hello”

29. Defined Constants 2 ways: Using pre-processor : #define
Example
#define pi 3.142
Using keyword : const
const int a = 1;

30. Example: Constant

31. Input & Output Stream Output  cout Input  cin
To display information on the computer’s screen
Example:
cout<<“Programming is great FUN!!”;
Input  cin
To read data typed from the keyboard
cout<<“please enter a number >>\n”;
cin>>val1;
**MUST include <iostream> header file

32. Input & Output Stream

33. Escape Sequence
Indicates that cout should do something out of the ordinary
When encountering a backslash (\) in a string, the compiler looks ahead at the next character and combines it with the backslash to form an escape sequence

34. Formatting Program Output
Besides displaying correct results, it is extremely important for a program to present its output attractively.
To include manipulators within an output display, must include the header file using the pre-processor command as follows:
#include <iomanip>
Most commonly used manipulators in a cout statement:
setw(n) – set field width to n
setfill(n) – sets fill character to n
setprecision(n) – sets floating –point precision to n

35. I/O Manipulator
Most system divides a page of text output into twenty five rows and eighty columns.
Example:
Suppose you want to create three column of output: person’s name, person’s student ID and person’s code program.

36. I/O Manipulator

37. I/O Manipulator: setfill(n)
Specifies character for blank space in field
Single quotes required around character enclosed in parentheses
Example:
num = ;
cout<<setw(10)<<setfill(‘*’)<<num;

38. I/O Manipulator Generating Left-Justified Value
Specifies character for blank space in field
cout.setf(ios::left);
By default, when we use setw(n) to print values or information, the values are right justified
So to put as left justify we must write the above statement.

39. I/O Manipulator Generating Decimal Point Value cout.setf(ios::fixed);
cout.precision(n);
Statement cout.setf(ios::fixed) forces the compiler to generate a fixed decimal output without exponential or e, notation.
Meanwhile cout.precision(n) dictates the number of decimal places to the right of decimal point to be generated.

40. I/O Manipulator

42. I/O Manipulator
The output of program:

43. Exercise Identify valid and invalid variable name:
Sum.of, 12345, newbal, c123, $balance
Write declaration statement to declare that the variable count will be used to store an integer
Write a declaration statement to declare that the variable initial will be used to store a character
Write a declaration statements for the following:
tempA,tempB and tempC used to store double – precision number
price, yield and coupon used to store single- precision numbers

44. Exercise
Write a relational expression to express the following condition (use your own variable name)
A person’s height is less than 6 feet
A length is greater than 2 and less equal than 3 feet
A person’s is older than 50 or has been employed at the company for at least 5 years.
Write a snippet code that can receive 3 input decimal number from user and prints the average of the numbers
Assign the sum of value variable marks1, marks2 and marks3 to variable totalMarks
Trace the output of the program
int mystery = 5;
mystery = 10 – 2 % mystery;
++mystery;
printf(“%d\n”,mystery++);