Intro Week 3

Variables

Scope

scope defines the life of a variable. Local Variables

Variables declared with functions/methods are only around as long as the function/method is running. These variables are known as local varables

Global Variables

Global variables are variables that are around for the entire length of execution. They are declared a public within the programs base class.
In c# since everything must be contianed in a class global variables do not really exist.

Block Level Variables

Block level variables exitist with the code block.
A code block is contained by { }.

Scope.cs

Assignment

The Assigment operator in c# is the '=' sign. You can assign variables like this...

<csharp>int myVar; //declare varible of type int called myVar myVar = 15; //assign myVar the value of 15 using the '=' sign</syntaxhighlight>

notice that the equals sign doesn't test for equality.

Branching

• if
• switch

If example

<csharp> int MyInt = 7;

if( MyInt > 10) {

 //Do this if MyInt is greater than 10

} </syntaxhighlight>

Multiple Ifs

<csharp> If Age >= 18

 Eligibility = ‘Yes’

Else If Age = 15

 Eligibility =‘Maybe’

Else

 Eligibility “No”

</syntaxhighlight>

<csharp> bool Eligible = false; //set the bool to false

</syntaxhighlight>

Comparison Operators

Operator	Description
==	Equality
<	Less Than
<=	Less than or equal to
>	Greater than
>=	Greater than or equal to
!=	Inequality

Logical Operators

Operator	Description
&&	Logical AND
II	Logical OR (note the II are really pipes)
!	Logical NOT

Boolean Expressions

Logical operators usually work on bollean expressions. Boolean expressions are is a statement that evaluates to true of false

(1 < 2)
or
(y == x)

Boolean expressions are often grouped with logical operator to combine comparisons

(x > 0) && (x <100) //x is greater than 0 and less than 100

(x < 0) || (x >100) //x is less than zero or x is greater than 100

Logical operator Precedence

1.  ! (NOT)
2. && (AND)
3. || (OR)

In class

Build a month namer. Ask the user to input a month number and our program will output the month name. How many ifs are we going to need?

Branching Statements

if

syntax

<csharp>if (expression)

   // statement
   

if (expression) {

   // statements
   // statements

} if (expression) {

   // statements
   // statements

} else {

   // statements

}</syntaxhighlight>

switch

syntax

switch (expression)

{
   case constant-expression:
           statement
           jump-statement
   [default: statement]
}

example 1

<csharp>// switch with integer type switch (myInt) {

   case 1:
           Console.WriteLine("Your number is {0}.", myInt);
           break;
   case 2:
           Console.WriteLine("Your number is {0}.", myInt);
           break;
   case 3:
           Console.WriteLine("Your number is {0}.", myInt);
           break;
   default:
           Console.WriteLine("Your number {0} is not between 1 and 3.", myInt);
           break;

}</syntaxhighlight>

In class

Redo month namer using a swtch rather than ifs

Home work

Write a program for converting student’s score into a letter grade. The program should ask to input a student score (between 0 and 100) then the program will display the grade earned by that score. Grade Points

A 90-100

B 80-89

C 70-79

D 60-69

F 59 or less