• Is more intelligent than human ??? – Of course Not! • A slave that only does what it is told • Is always right; can never be wrong • Good at performing lengthy and recurring tasks

1. Agenda
•Computer
•Program
•Human Vs. Computer Instruction
•Programming Languages
•Interpreter & Compiler
•Memory
•Recursion
•Modularity

2. Computer
• Is more intelligent than human ???
– Of course Not!
• A slave that only does what it is told
• Is always right; can never be wrong
• Good at performing lengthy and recurring tasks

3. Program
•A set of instructions that tells the computer what to
do.
–Takes input(s)
–Processes input(s)
–Produces output(s)
–Garbage In, Garbage Out (G.I.G.O.)
•Computer executes the program exactly as you have
instructed it. It will do no more or no less than what is
contained in your specific instructions.

4. Human Vs. Computer Instructions
• Ahmed throws the ball fast
Subject Action Object
Ahmed Throw Ball
Computer
Function Throw(ball)
{
1. Lift the ball.
2. Move hand in backward direction
3. Move hand in forward direction exerting good amount of force.
4. Leave the ball.
}
Computer instructions will be executed how it tells to do.
Human instruction execution may change every time you instruct.

5. Programming Languages
•Low Level Languages
–Machine Code
–Assembly Language
•High Level Languages
–C#, X++, C etc.
int a = 10;
int b = 20;
int result;
result = a + b;

6. Interpreter and Compiler
•A computer can only understand machine language, therefore we need
a program which can translate high level into machine language.
•A program is translated into machine language by interpreter or
compiler.
•Interpreter
–Each instruction is interpreted from the programming language as
needed (line by line of code).
–Every time the program is run, the interpreter must translate each
instruction again.
–E.g.
•PHP, JavaScript, Pearl, Python etc.
•Compiler
–A compiler makes the translation once so that the source code don’t
have to be translated each time the program is run.
–Compiler take less time for execution since it translates code once.
–E.g.
• C#, Java, X++ etc. too.

7. Memory
• While a program is running, its data must be stored in
memory.
• A running program uses two regions of memory to
store data.
• –Stack
• –Heap
• How much memory is required for an item, and where
and how it’s stored, depends on its type.
• Language runtime takes care of memory allocation.
• For X++ the Microsoft Dynamics AX runtime manages
the storage allocation of data on stack and heap.

8. Stack
• A stack is an array of memory that acts as a last-in, first-out (LIFO) data
structure.
• Stack-based memory allocation is very simple and typically faster than
heap-based memory allocation
• Data can be added to and deleted only from the top of the stack.
• Placing a data item at the top of the stack is called pushing the item onto
the stack.
• Deleting an item from the top of the stack is called popping the item from
the stack.

9. Heap
• Chunks of memory are allocated to store certain
kinds of data objects.
• Memory can be stored and removed from the
heap in any order.
• Heap is also known as dynamic memory.

10. Data type
A classification for identifying one of various types of data
•A type as a template for creating data structures.
•A type is defined by the following elements:
–A name.
–A data structure to contain its data members.
–Behaviors and constraints.
E.g.
–Integer
•32 bit or 64bit, stores integers only.
–Boolean
•1 byte, true or false.
–Real
•64 bit, floating point numbers.

11. Data type
There are two kind of data types:
Value type
–Stored in stack.
–Require only a single segment of memory.
–E.g.
•Integer
•Boolean
•Real
Reference type
–Require two segments of memory
–The first contains the actual data—and
is always located in the heap.
–The second is a reference that points to
where in the heap the data is stored.
–E.g.
•String
•Object

12. Variables
The name, or identifier, for a variable points to a memory location
where information of a specific data type is stored.
•Names must be limited to ASCII letters, digits, and the underscore
character (_).
•Letters can be either uppercase or lowercase.
•The first character must be either a letter or the underscore
character.
•Best Practice, variable names should begin with a lowercase
letter i.e. Camel Casing.
–myVariable, custTable
•Why use Variables ?
–Variables can maintain the same value throughout the program.
–Changing value at one place will reflect throughout the scope.

13. Variable Declaration
Variable always be declared with some data type.
Declaration with initialization
Multiple Declaration
–The variables in a multiple-variable declaration must all be
of the same type.
–The variable names must be separated with commas.

14. Method
Lines of code that perform a specific task.
–[ Modifiers ] ReturnType MethodName( ParameterList )
{
//body
}
Public void Test(int i)
{
}
Modifiers public | protected |
private|static
ReturnType Datatype | void
MethodName Identifier
Parameter Datatype Variableidentifier [ =
Expression ]

15. Method Example
Return sum of any two integers.

16. Method Invocation
•Execution of the current method suspends at that point
of the invocation.
•Control transfers to the beginning of the invoked
method.
•The invoked method executes until it completes.
•Control returns to the calling method.

17. Method Parameters
• By Value
• –It allocates space on the stack for the formal
parameters.
• –It copies the values of the actual parameters to
the formal parameters.
• By Reference
• –It copies the address of variable not the value.
• –The actual parameter must be a variable.

18. By reference & By Value Example

19. •Local variable
–Alive until method returns.
•Global variable
–Alive until application shutdown.
–Company Name
•Constants
–Once set, the value cannot be changed
–Must be used instead of hard-coded values
–E.g. Labels file
Variable Scope

20. Variable Scope Example

21. Control Statements
Conditional
•Skip part of code or execute only desired portion
–If
–If Else
–If Else-if Else
–Switch
Loops
•Executes same lines of code once or more than one time
–While
–Do - While
–For

22. Conditional- if-[else-if] – [else]
if statement evaluates a question (condition).
•Executes a statement(s) if condition is true.
•Syntax
if(expression)
{
statement
}
[ elseif(expression) //can have multiple elseif
// statements
{
statement
}………
else // only one else statement
{
statement
}
]

23. Recursion
•Recursion can be used to manage repetition.
•Recursion is a process in which a module
achieves a repetition of algorithmic steps by
calling itself.
•Each recursive call is based on a different,
generally simpler, instance.

24. Fundamental Rules
Base Case
–Always have at least one case that can be solved without
recursion.
Make Progress
– Any recursive call must progress towards a base case.
Always Believe
– Always assume the recursive call works.
Compound Interest Rule
– Never duplicate work by solving the same instance of a
problem in separate recursive calls.

25. Recursion Example
Calculating 5!
Input n = 5;
Factorial (n);
120
•5* a where a = Factorial(n -1)
a = 24
•4* a
a = 6
•3 * a
a = 2
•2* 1