Intro Week 3
Contents
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 { }.
Assignment
The Assigment operator in c# is the '=' sign. You can assign variables like this...
int myVar; //declare varible of type int called myVar
myVar = 15; //assign myVar the value of 15 using the '=' sign
notice that the equals sign doesn't test for equality.
Branching
- if
- switch
If example
int MyInt = 7;
if( MyInt > 10)
{
//Do this if MyInt is greater than 10
}
Multiple Ifs
If Age >= 18
Eligibility = ‘Yes’
Else If Age = 15
Eligibility =‘Maybe’
Else
Eligibility “No”
bool Eligible = false; //set the bool to false
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
- ! (NOT)
- && (AND)
- || (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
if (expression)
// statement
if (expression) {
// statements
// statements
}
if (expression) {
// statements
// statements
}
else {
// statements
}
switch
syntax
switch (expression)
{ case constant-expression: statement jump-statement [default: statement] }
example 1
// 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;
}
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