1. Data Types and Expressions
AKEEL AHMED

2. Overview Identifiers Variable and Literal Types, Classes, and Objects
Converting data types
Arrays

3. What is Identifiers?
Identifiers are names of elements that appear in a program, such as data items.
predefined identifiers
System, Main, Console, and WriteLine.
user defined identifiers class name like TestClass, method name like sum

4. C# Keywords/Reserve words
From MSDN

5. Variable and Literal Value
A variable represents an area in the computer memory where a value of a particular data type can be stored.
Declaring a variable
type identifier = expression;
int examNumber=23;
Literals are the numbers, characters, and combinations of characters used in your program

6. Types, Classes, and Objects
Types: A kind of group that can be differentiated from other kinds of groups by a particular set of characteristics
Classes: Types are actually implemented through classes in C#. The Framework class library, which is part of .NET, includes over 2000 classes that you can use in your programs.
Objects: an object is an instance of a class

7. Predefined Data Types

8. Predefined Data Types

9. Variables (Syntax)
int i = 7; double d=45.8; float fValue= 23f; string message = "Welcome"; object obj = new object(); bool male = false; decimal n3 = 1.234m;

10. Consts (Syntax)
Variable is a place in memory that can be changed const int constValue = 50; constValue = 51; // Will cause compilation error

11. Converting data types
Explicit conversion (also known as cast ) – Programmer forces the conversion and takes the risk of loosing data. byte b = 128; int i = b;

12. Converting data types
Implicit conversion – Conversion is done by the complier automatically. No data is lost because of the conversion. Example: converting byte value (range: 0 to 255) to integer value (range: to ). decimal pi = 3.14; int notPi = (int)pi;

13. Converting data types
Other conversions – Sometimes one needs to convert not-compatible types – for example convert string value “123” to integer value 123. For such case there are usually special methods. string text = "123"; int number = int.Parse(text); // number == 123

14. Arrays (Syntax)
The array is a complex data type which handles a collection of elements. Each of the elements can be accessed by an index. All the elements of an array must be of the same data type. int[] numbers = new int[5]; numbers[0] = 3; numbers[1] = 2; numbers[2] = 1; numbers[3] = 5; numbers[4] = 6; int len = numbers.Length; for (int i=0; i<len; i++) { Console.WriteLine(numbers[i]); }