CISC 110Day 2

Programming Basics

Outline

• Comments• Data Types• Conditional Statements (Branching)• Loops• Functions• Variable Scope

2

Comments

Two Ways to Comment Code:

// This is a comment

/*

This is a comment spanning multiple

lines

*/

3

Data Types

Integer (e.g. 5)

Number (e.g. 5.5)

String (e.g. “Hello!”)

Boolean (true/false)

4

Comparison Operations

Operators: == (is equal to)!= (not equal to)> (greater than)>= (greater than or equal to)< (less than)<= (less than or equal to)

5

Boolean Data Type

6

Example:

var x:Boolean;

x = (1 == 1);

trace(x);

Output: true

Conditional Statements

Statements: if (…something is true…)

{…execute these lines of code…

}else

{…else, execute these lines of code…

}

7

Conditional Statements

8

Example:

var x = 10;

if(x <= 100)

{

trace(“Howdy!”);

}

Output: Howdy!

Conditional Statements

9

Example:

var x = 100;

if(x <= 10)

{ trace(“Howdy!”);}

else

{ trace(“Heya”);}

Output: Heya

Logical Operators

Operators:

&& (and) e.g. (true && true) == true

(true && false) == false

|| (or) e.g. (true || false) == true

10

Logical Operators

11

Example:

var x = 1;

var y = 2;

if((x == 1) && (y == 2))

{

trace(“Howdy!”);

}

Output: Howdy!

While Loop

Statement:

while (…something is true…)

{

…execute these lines of code…

}

12

While Loop

13

Example:

var x = 1;

while(x < 10)

{

x += 1;

}

trace(x);

Output: 10

For Loop

Statement:

for(…until condition is not true…)

{

…execute these lines of code…

}

14

For Loop

15

Example:

for(var k = 1; k < 10; k = k + 1)

{

trace(“!”);

}

Output:!

!

!

!

!

!

!

!

!

For Loop

16

Example:

for(var k = 1; k < 10; k++)

{

trace(“!”);

}

Output:!

!

!

!

!

!

!

!

!

Functions

17

Example:

function displayMessage()

{

trace(“I\’m in a function!”);

}

displayMessage();

Output: I’m in a function!

Function with Argument

18

Example:

function displayMessage(message:String)

{

trace(message);

}

displayMessage(“I\’m in a function!”);

Output: I’m in a function!

Function with Arguments

19

Example:

function displayMessage(m1:String, m2:String)

{

trace(m1+m2);

}

displayMessage(“Well…”,” Hello…”);

Output: Well…Hello…

Function with Return Value

20

Example:

var s:String = “”;

function createMessage(x:String):String

{

return “Hello “ + x + ”!”;

}

s = createMessage(“CISC 110”);

trace(s);

Output: Hello CISC 110!

Variable Scope

21

Scope means where variables exist, and can therefore be accessed, in a program.

Local Variables: Variables defined inside a function only exist within that function. They are created when the function starts executing and are destroyed when it finishes.

Global Variables: Variables defined outside of a function exist everywhere after they’re defined, except inside a function with a duplicate variable name.

Variable Scope

22

Example:

var s:String = “”;

function createMessage(x:String)

{

return “Hello “ + x + ”!”;

}

s = createMessage(“CISC 110”);

trace(x);

Output: undefined

Null

23

null: A variable can be assigned to the value “null” (e.g. var x = null;).

undefined: Variables should not be assigned to the value “undefined” – this is the value automatically assigned to variables that have not been assigned to any other value.