1. Basic Elements of Computer Program
Week 2

2. Topic 2 - Outline Identifier Data types Arithmetic Operator
Arithmetic Expression
Assignment Statement
IO Statement
C++ Program Structure
Programming Process
Control Structure
Topic 2 - Outline

3. What? Name assigned by user
Identifier
What? Name assigned by user
Why? To represent programming entities such as variable, function or constant
Rules?
The 1st character must be an alphabet letter or an underscore ‘_’.
Can only consists of letters, digits and underscore ‘_’.
Cannot use C++ reserved words/keywords
There must be no blank space character
Identifiers are case sensitive

4. Reserved Word It has predefined meaning for the language. int char
long
float
double
default
case
for
void
break
const
else if
private do
goto
switch
while
public
class
return
continue

5. Variable Rules? What? Memory location in computer.
Must begin with a letter or underscore (_), and may only contain only letters, underscore, or digits.
Variable name cannot be a keyword.
Variable name cannot consists of more than 31 characters.
Variable
What? Memory location in computer.
Why? To store data/instructions
How? Store a data at a time
Variable value might be changed during program execution
Must declare before used
Must assign / initialize a value to variable before use it
Rules?

6. Variable Declaration
Syntax: data_type variable; Example: int x; int number1, number2, number3;
Please take note of the coma to
Separate the variable list &
Semicolon to end the variable declaration

7. Variable: what happen when a variable is declared??
The compiler allocates a memory space for the variable.
In the memory space, name, data type and value of the variable are stored.
ex.
Allocates a memory of 4 bytes with address the information stored in the memory space are variable name (area), data type (float).
float area;

8. Constant
Values that are fixed and do not change throughout program execution
Declaring a constant:
Using const keyword

9. Constant Declaration
Syntax: const data_type constant_name = value; const float PI = 3.14;
Data type
const keyword
Constant_name
value

10. Legal and Illegal Identifiers
The following are legal identifiers in C++:
first
conversion
payRate

11. Data Types
Numeric
Int
Float
Double
Character
Char

12. Numeric Data Type Integer Floating point
Whole number – positive, zero or negative
C++ keyword
int, long int, long long int
Floating point
Numbers with decimal points
float, double
int area;
float area;

13. int Data Type Examples:
-6728 78
Positive integers do not have to have a + sign in front of them
No commas are used within an integer
Commas are used for separating items in a list

14. float, double Data Type
Is a decimal number that contains the decimal point (.)or the exponent (e) or both.
float data type can hold values up to six or seven significant digit accuracy.
double data type can hold values up to 14 or 15 significant digit accuracy.

15. Character Data Type char Single character Example: char name;
Store one character value
C++ keyword
char
Example:
char name;

16. char Data Type The smallest integral data type
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', '*', '+', '$', '&'
A blank space is a character and is written ' ', with a space left between the single quotes

17. char[] Data Type Sequence of characters
It stores sequence of zero or more characters
Enclosed in double quotation marks
Null: no characters is stored.
Each character has relative position
Position of first character is 0, the position of the second is 1, and so on
Length: number of characters in a sequence
C++ keyword
char[]
char name[5];
Note: the double quotes and
Single quotes

18. Initialization
A variable can be initialized to any value as long as the value’s data type matches the variable’s data type.
Syntax:
datatype variable [ = initialValue ];
Examples:
int age = 0;
float rate = 0.0;
double sale = 0.0;
char grade = ‘ ’;
char company[20] =“ ”;

19. SUMMARY OF DATA TYPE Category Data types Keywords Bits Range Examples
Numeric
integer
int 16
to 32767
45, 0, -10
long integer
long 32 to
-37876
floating point
Float
6 digit precision
32.88, -89.5
double floating point
double 64
12 digit precision
Character
char 8
‘c’, ‘v’
Sequence of character
char[ ]
“hello”, “sarah”

20. OPERATORS
A Symbol that tells the compiler to perform specific mathematical or logical manipulations
Types of operator:
Arithmetic operators
Assignment operators
Relational operators
Logical operators

21. Arithmetic Operator Addition + Subtraction - Division / Multiplication*
Modulus %

22. Precedence & Associativity
Precedence of operator
Precedence rules:
specify which operator is evaluated first when two operators with different precedence are adjacent in an expression.
Associativity rules:
specify which operator is evaluated first when two operators with the same precedence are adjacent in an expression.
Highest
Operators
Associativity ()
Left to right
* / %
Lowest

23. Precedence & Associativity
Example 1:
Example 2: 4 + 2 * 3 3 * 4 / 2

24. Arithmetic Expression: Operands & Operator
One of the input of an operator
Example:
3 + 6
Operator
Operand

25. Several rules that you need to follow to evaluate arithmetic expression:
If one or more operand(s) in an arithmetic expression has/have data type double, the resulting expression is of data type double.
If all operands in arithmetic expression are of type int, the resulting expression is of type int.

26. Arithmetic operators Require two operands Ex. +, -, *, /, %
For the modulus (remainder) operator, all of its operands must be integer only.
Be careful of the operands’ data types when using division operator. For example,
Expressions
Output
7 / 4 1
7.0 / 4
1.75
-1 / 4
-1 / 4.0
-0.25

27. Example
3 * 7 – * 5 / (3 * 7) – 6 + ( (2 * 5) / 4 ) + 6 = 21 – 6 + (10 / 4) + 6 (Evaluate *) = 21 – (Evaluate /) = (Evaluate -) = (Evaluate first +) = 23 (Evaluate +)

28. Assignment statement
Assigns a value to respective memory space allocated to a variable.
May involve arithmetic expressions.
Syntax:
Examples
variable = value/ variable;
a = 3;
x = 5.6;
y = ‘z’;
pi = 3.14;
5 = z; //invalid!!

29. Assignment statement Syntax:
The expressions may contains variables, constant and arithmetic operators,
Example:
variable = expression;
float radius, pi, area;
radius = 3;
pi = 3.14;
area = pi * radius * radius;

30. Assignment statement A sequence of character:
Using assignment statement:
Using strcpy function:
char a [20] = “sample string”;
char a [20];
strcpy(a ,“sample string”);

31. Writing algebraic expression using C++ statement.
Algebraic statement
pow(a,b) ab
sqrt(a - b)
√ (a – b)
abs(x - y)
| x – y |

32. Arithmetic Expression
Examples
Algebraic Expression
Arithmetic Expression
17–
23 – 7 5
23 – 7 / 5 4
( ) / 4 42
pow ( 4 , 2 )
 ( a – b)
sqrt (a – b )
 x – y 
abs ( x – y )

33. Examples: -b ± √b2 – 4ac 2a Solution : Or
-b + sqrt ((pow (b,2) – (4 * a * c))/(2 * a) Or
-b - sqrt (b * b – 4 * a * c) / (2 * a)

34. IO Statement: Output statements
Used to display information on screen.
The header file iostream.h must be included in the preprocessor directives.
Syntax:
The symbol << is called insertion operator
cout<<variable<<variable<<…<<variable;

35. Output statements Sample output: … year = 1999;
cout << “my year of birth is”<<year;
my year of birth is 1999

36. cout << (2003 – year);
Output statements
The operand after the symbol << can be a constant, variable or an expression.
The following are escape sequence which can be used in a string literal in a cout statement.
cout << (2003 – year);
\n – new line
\’ – single quote
\t - tab
\” - double quote
\b - backspace
\\ - backslash

37. IO Statement: Input statement
Used to read in information from a keyboard.
Syntax:
The symbol >> is called an extraction operator.
The operand after the symbol >> must be a variable.
cin>>variable>>variable>>…>>variable;

38. Input statement: example…
cout << “enter your age and matric number:”;
cin>>age>>matric;

39. Input statement
cin only takes input up to the first blank (ignores whitespace such as blanks, tabs).
When reading a sequence of character (including whitespace), used:
cin.getline(name, 20);

40. Example Using cin statement: Sample output
cout<< “Enter your name:”;
cin>>name;
cout<< “Welcome, ”<<name<<“!”;
Enter your name: Adam Ahmad
Welcome, Adam!

41. Example Using cin.getline statement: Sample output
cout<< “Enter your name:”;
cin.getline(name,20);
cout<< “Welcome, ”<<name<<“!”;
Enter your name: Adam Ahmad
Welcome, Adam Ahmad!

42. C++ Program Structure Components of the program
Preprocessor directives
Constant and type definition section
Main program heading
Begin block
Main block
Declaration section
Statement section
End block

43. Syntax
#include <headerFileName>
const <dataType><identifier> = <value>
dataType <identifier>
<functionType> <functionName> (formal parameter list) {
cout << statement;
cin >> variables; }

44. A C++ program is a collection of one or more subprograms, called functions
A subprogram or a function is a collection of statements that, when activated (executed), accomplishes something
Every C++ program has a function called main

45. Preprocessor directives
Examples:
#include <iostream.h>
To declares the basic C++ streams (I/O) routines.
#include <math.h>
Declares prototypes for the math functions and math error handlers.
#include <conio.h>
Declares various functions used in calling the operating system console I/O routines.

46. Example of program Preprocessor Directives main function
#include <iostream.h>
#include <conio.h>
#include <string>
void main() {
string name;
int age;
cout<< "Please enter your name:\n";
cin>>name;
cout<< "Please enter your age:\n";
cin>>age;
cout<<endl;
cout<< "Your name is:"<<name<<endl;
cout<< "Your age is:"<<age<<endl;
getch(); }
Preprocessor Directives
main function

47. Programming process

48. Compilation process

49. Running a program

50. Control Structure: Sequential Control Structure
The simplest of all the structures
The program instruction has one starting point and one ending point.
Each step is carried out in order of their position and is only done once.

51. Sequential Control Structure
Flowchart
Begin
Fill a kettle with water
Boil the water in the kettle
Put tea leaves in the pot
Pour boiling water into the pot
End

52. Control Structure: Selection Control Structure
The selection structure allows comparison of expression, and based on the comparison, to select certain course of action

53. Selection Control Structure
Telephone
rings? F T
Continue reading
Answer phone

54. Control Structure: Repetition control structure
The repetition structure allow a sequence of instructions to be executed repeatedly until a certain condition is achieved.

55. Repetition control structure
beg has items?
false
true
Take item out

56. Control Structure: Modular
Is a method of dividing a problem into separate tasks, each with a single purpose.
Separate task with a single purpose = FUNCTION

57. Modular
Company IT
Accountancy
Human resource