1. Chapter 2

2. Chapter 2 Namespaces Input and Output
List of some classes in System, Math etc
Compile and execute sequence

3. Typing C# is a strongly “typed” language
Most formal languages are (C++, Cobol, Java)
Cannot mix numbers and characters
Must know how big number will get

4. Data Types Short (16 bit integer) Char (16 bit character)
Float (32 bit floating point number)
Boolean

5. More on Data Types Numeric Character or String Boolean
Integer (short, long, byte)
Floating point (for decimal fractions)
Decimal (with M suffix for money) 96 bits
Double (includes decimal places)
Character or String
Any character that has to appear
Boolean
Represents logical values (TRUE OR FALSE)

6. Numeric Integer Double (the default type) Decimal Floating Point
Short(16) , long (32 bits), or byte (8bits)
Literals – when you use a value in the program
Double (the default type)
Up to 15 decimal digits
Decimal
Up to 28 digits
Floating Point
Used to describe numbers with decimals
Use ‘double’ to ensure full representation

7. Many characters (a sentence)
One character within single quotes (‘x’)
String
Many characters (a sentence)

8. Boolean
Bool data stores logical result (true or false)

9. Conversion Sometimes programmer needs special variable
Two types in C#: Implicit and Explicit
Compiler protects user from unsafe choice
Casting converts inline: float pi=(float) 3.14
Default is double for Fl Pt literals
Casting overrides the double and allows cast

10. Program Style We listed some // comments earlier
We also should have 4 sections in every program
// declare section (where you assign variables etc)
// input section (accept user input)
// computations (where you do calculations)
// display results
IN THAT ORDER

11. using System;
namespace WTprog1 {
// wt
// program 1
// due date" 1/31/05
class Class1
static void Main(string[] args)
// declare section
// input section
// computation section
// display section
}// end Main
}//end class
}// end namespace

12. Variables To assign a value to an integer: int age; age = 5;
int tells the compiler that an integer follows
age is the case-sensitive variable name
5 is the value that will be stored in age
If you had a statement to display the value,
Console.WriteLine(“age is ” + age);
Console.WriteLine(“Age is {0}”, age);

13. Variables Contd To assign a character value to a variable:
char name = ‘d’;
Notice the single quotes?
In C# each character occupies 16 bits, so that even Japanese etc can fit
You use string to input a whole name
name=“Smith”

14. Printing Your program: string name = “jones”; string major = “IS”;
string yr = “02”;
Console.WriteLine(“My name is ” + name);
Console.WriteLine(“Major: ” + mj+ “ year ”+yr)
Console.WriteLine(“Major: {0}, Year: {1}”, major, yr;