What is Variable, Datatype and C# Datatypes

Variables :

• It is location in memory (RAM) to temporary store a value during execution of Program / Software.
• As the name suggests, the value of variable can change during execution of program.
• A variable is made of 3 things.

                - Datatype
                - Name
                - Value (optional)

DataType :
   - It means what type of value we can store in the variable.

• Numbers such 123, 10.50 etc
• Strings such as UK, Canada etc
• Data such 11/4/2020

Name :

• It identifies the variable. For example, firstName, lastName, age

Value :

• What actual value is stored in variable.

List of DataTypes in C# :

1. Integer → Numbers such as 120, 345 etc
2. Decimal → Number such as 3.5, 4.5 etc
3. Char → Single character such as A,a,B,z
4. Bool → True or False value
5. String → More than one characters value such as John Smith, Mark Smith, Canada , Landon etc.

Syntax :
              DataType variableName = value;

Naming Rules :
 一  Names may consists of letters (A-Z or a-z), digits and underscores

•  e.g firstName, firstNumber, _Age, firstNumber1 (correct)
• #FirstName, @Email (wrong)

一 Name must begin with a letter or underscore.

• e.g. firstName or _firstName (correct)
• 1stName or 2ndNumber (wrong)

一Name must not have spaces.

• e.g. first Name (wrong)
• firstName (correct)

一 Names must not have reserved word or C# keywords. List of C# keyword are shown in the table.

Naming Conventions :
ー Names must be meaningful

• e.g. firstNameString, cnicString, studentldlnteger (correct)
• a,b, obj1 (wrong)

ー  Name must include its datatype

• e.g. firstNameString, cnicString, studentldlnteger (correct)
• FirstName, firstname, CNIC or Studentld (wrong)

ー Name must begin with lowercase letter and then capitalize each word of the name

• e.g. firstNameString, cnicString, studentldinteger (correct)
• FirstName, firstname, CNIC or StudentId (wrong)