Sunday, 26 April 2020

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)



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