Introduction to Data Types

Data types:

 

 Data type specifies size and type of data.

 

Computer Memory capacity is measured in bytes

1 byte = 8bits(01010101)

1 bit = 0 (or) 1

 

Data types in C#.Net can be categorized into 5 types

 

I) Numeric datatype:

   

  Numerical

  

     A) Signed:                               

   

         1)sbyte---1byte

              

1       sbyte: Holds 8-bit signed integers. The s in sbyte stands for signed, meaning that     the variable's value can be either positive or negative. The smallest possible value for an sbyte variable is -128; the largest possible value is 127

        

       2)short----2 bytes

 

2       short: Holds 16-bit signed integers. The smallest possible value for a short variable is -32,768; the largest possible value is 32,767.

    

         3)int---4 bytes

 

3       int: Holds 32-bit signed integers. The smallest possible value of an int variable is -2,147,483,648; the largest possible value is 2,147,483,647.

         4)long---8 bytes

Ø          long: Holds 64-bit signed integers. The smallest possible value of a long variable is 9,223,372,036,854,775,808; the largest possible value is 9,223,372,036,854,775,807.

 

 

   

 

 

 

 

 

B)Unsigned:  

        

          1)Byte --- 1 byte

 

4       byte: Holds 8-bit unsigned integers. Unlike sbyte variables, byte variables are not signed and can only hold positive numbers. The smallest possible value for a byte variable is 0; the largest possible value is 255.

       2) ushort--- 2 bytes

 

Ø ushort: Holds 16-bit unsigned integers. The u in ushort stands for unsigned. The smallest possible value of an ushort variable is 0; the largest possible value is 65,535.

 

       3)uint--- 4 bytes

 

5       uint: Holds 32-bit unsigned integers. The u in uint stands for unsigned. The smallest possible value of a uint variable is 0; the largest possible value is 4,294,967,295.

       4)ulong---8 bytes

 

6       ulong: Holds 64-bit unsigned integers. The u in ulong stands for unsigned. The smallest possible value of a ulong variable is 0; the largest possible value is 18,446,744,073,709,551,615.

VB.Net doesn’t have unsign data types.

 

II)Floating point datatype:   

 

      1)Float--- 4 bytes

7       float: Holds a 32-bit signed floating-point value

      2)Double--- 8 bytes

8       double: Holds a 64-bit signed floating-point value

      3)Decimal--- 16 bytes

9       decimal: Holds a 128-bit signed floating-point value

 

III)Character related:

  

         1)Char- 2 bytes(with Unicode characters)

        

10  char: Holds 16-bit Unicode characters. The smallest possible value of a char variable is the Unicode character whose value is 0; the largest

 possible value is the Unicode character whose value is 65,535.

 

       Unicode characters:

 

11  Fundamentally, computers just deal with numbers. They store letters and other characters by assigning a number for each one. Unicode provides a unique number for every character, no matter what the platform, no matter what the program, no matter what the language.

 

1V)Logical data types:

         -

        1)bool--- 1 byte

12  bool: Holds one of two possible values, true or false.

                It can hold only true/false as values.

 

 

 

 

V)General data types:

 

           1)String:

 

13  string: Represents a string of Unicode characters. It allows easy manipulation and assignment of strings

           2)Object:

 

14  object: Represents a general purpose type. In C#, all predefined and user-defined types inherit from the object type or System.Object class.

 

     String and Object data types do not have predefined sizes.

 

 

 

 

 

 

 

Value & Reference types:

 

Based on the storage C# data types can be categorized into 2 category.

 

 

 

-Value type

 

1       Stack based

 

In the case of value type, memory is allocated on the stack which works on LIFO(Last in first out) approach as far as memory allocation and de-allocation is concerned.

 

Stack is a data structure, which works on LIFO approach.

Data structure defined as collection of related data.                                                                                                                           

 

-Reference type

                   

2       Heap based

Reference type supports heap-based memory allocatin,memory is allocated in the free pool of unused area called the heap .The size of the memory is determined at run-time, and the memory de-allocation is subjected to Garbage Collector.

 

In contrast, the heap can be pictured as a random jumble of objects.  Its advantage is that it allows objects to be allocated or deallocated in a random order.  As we’ll see later, the heap requires the overhead of a memory manager and garbage collector to keep things in order

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Difference between Value types and Reference types

Value Types                                               Reference Types

1)Memory is allocated  on the Stack	1)Memory is allocated on the heap
2)A value type variable contains the data itself.	2)Reference type variable contains the address of memory location where data is actually stored.
3)Examples for Value types      a)Primitive data type      b)Structures      c)Enumerators	3)Examples for reference types    a)Classes    b)Interfaces    c)Delegates