1. BASIC ELEMENTS OF A COMPUTER PROGRAM

2. Contents 1. Statements 2. C++ Program Structure 3. Programming process
4. Control Structure

3. statements

4. Assignment statements

5. Assigns a value to respective memory space allocated to a variable.
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!!

6. 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;

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

8. Exercises
Write a C++ assignment statement that assigns the letter T to a char variable named insured.
Write a C++ assignment statement that multiplies the number by the content of a double variable named hours, and assigns the result to a double variable named grossPay.
Assuming the answer variable is an int variable, the assignment statement answer=8/4*3-5%2; assign the value ______ to the answer variable.
What will be assigned to the answer variable in question 3 if the variable is a double variable?

9. Converting algebraic expression into C++ statements

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

11. 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 )

12. 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)

13. Exercises
s = t3 – uv3
g = 4∏2 a3
p2(m1+m2)
3) a = 2x + y
3(x – y)+ 2
4) a = 2(x2 + y)
x – y x + y

14. Exercises
a = √ x + y
a = 2 √ x + y2 7
a = p √x – y
√ x + y

15. Input output statements

16. Used to display information on screen.
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;

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

18. 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

19. Used to read in information from a keyboard. Syntax:
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;

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

21. When reading a sequence of character (including whitespace), used:
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);

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

23. Using cin.getline statement:
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!

24. C++ Program structure

25. Components of a program
Preprocessor directives
Constant and type definition section
Main program heading
Begin block
Main block
Declaration section
Statement section
End block

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

27. 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

28. 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.

29. 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

30. Programming process

31. Compilation process

32. Running a program

33. Control structures

34. 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.

35. 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

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

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

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

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

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

41. Modular
Company IT
Accountancy
Human resource

42. Thank You !