1. © 2007 Lawrenceville Press Slide 1 Assignment Statement An assignment statement gives a value to a variable. Assignment can take several forms: x = 5; a literal (5) is assigned to x x = y + 2; the value of an expression (y + 2) is assigned to x x = z; the value of another variable ( z ) is assigned to x

2. © 2007 Lawrenceville Press Slide 2 Variable Assignment A variable can store only one value at any time. int x; x = 5; x = 10; x 5 10

3. © 2007 Lawrenceville Press Slide 3 Primitive Data Types TypeStorage Required int 4 bytes double 8 bytes char 2 bytes boolean 1 bit

4. © 2007 Lawrenceville Press Slide 4 Abstract Data Types A variable declared with a class is called an object. For example, the object spot is type Circle: Circle spot = new Circle(4);spot getRadius() area()

5. © 2007 Lawrenceville Press Slide 5 C# Packages Numerous packages are included with C# Packages contain classes Packages can be added to an application with an Using statement. For example, the statement Using System; makes the Scanner class and its methods accessible to the application.

6. © 2007 Lawrenceville Press Slide 6 Integer Division Integer division ( / ) is performed when both operands are integers. Only the integer portion of the quotient is returned:

7. © 2007 Lawrenceville Press Slide 7 Real Division Real division ( / ) is performed when one or both operands are type double. The entire quotient, including the decimal portion is returned: double result; result = 20.0/7.0;//result is 2.857

8. © 2007 Lawrenceville Press Slide 8 Modulus Division Modulus division ( % ) returns the remainder of a division operation:

9. © 2007 Lawrenceville Press Slide 9 Operator Precedence Operators in Java have the following precedence: 1. multiplication and division 2. addition and subtraction Operators of the same precedence are evaluated in order from left to right. For example, multiplication is performed first, then division, and finally addition: 5 + 6 * 4 / 2 = 17

10. © 2007 Lawrenceville Press Slide 10 Changing the Order of Operations The order in which operators are evaluated can be changed by using parentheses. For example, addition is performed first, then multiplication, and finally division: (5 + 6) * 4 / 2 = 22

11. © 2007 Lawrenceville Press Slide 11 Type Casting Type Casting converts a number of one type to a number of a different, but compatible type. Type casting is used to: 1.make the operand types in an expression match. For example, wholeNum = (int)y * 2 2.truncate the decimal portion of a double. For example, wholeNum = (int)z 3.change the way in which a division ( / ) operation will be performed. For example, realDivision = (double)a / (double)b

12. © 2007 Lawrenceville Press Slide 12 Programming Errors Syntax errors violate the rules of C#. Logic errors, also called semantic errors, occur in statements that are syntactically correct, but produce undesired or unexpected results. Run-time errors, also called exceptions, halt program execution at the statement that cannot be executed. One type of exception is called DividByZeroExecption.