Understanding Heap and Reference type

Hello all,

In continuation to my previous post Understanding Stack and Value type, Now I am going to explain what is Heap memory? and what is Reference type? Let's start,

Basically here I mean Heap is memory. Reference type is data which are stored in this memory. Consider the below diagram,

In the above code I declare two variables as data type object. As Microsoft definition "The object type is an alias for System.Object in the .NET Framework. You can assign values of any type to variables of type object." When the first line of code (object i=1;) executed, like value type here too the space allocated in Stack memory. But Stack memory having reference address only. Originally data stored in heap memory. For better understanding see image below,

In the second line we just reassigned the i value to y, So the memory allocation should be like below,

So above picture clearly shows, Reference types data would not reallocate the memory for reassign. 

Points to remember

• Other than Dot net data types such as Object, user defined data types (Class) are called Reference types. 
• Memory used to store the Reference types data is called Heap Memory. 
• When the Program execution has stopped, Stack memory has cleared automatically. But Heap memory will not be cleared automatically. 
• Heap memory is cleaned by Garbage Collector.
• Generally value types are faster than Reference types, because in reference types boxing will occur

Understanding Stack and Value type

Welcome buddies,

In my previous post I have explained C# - Dot net datatypes. Now I am going to explain what is Stack, Heap memory? and what is Value type and Reference type? Let's start,

Basically here I mean Stack is memory. Value types is data which are stored in this memory. Consider the below diagram,

In the above code I declare two integer variable i,y and assign value 1 to i. Also reassign the i to y. In  C# - Dot net datatypes I mentioned integer datatype will get 32 bytes memory to represent the value. So when first code executed, a chunk of memory allocated which size would be 32 bytes. 

In the second line we just reassigned the i value to y, So the expected memory allocation should be like below,

But the actual allocation be like below image,

That means It allocates new chunk of memory for the y. So we conclude definition "When the values reassign instead of reuse the previously allocated memory, if new chunk of memory is created then the data is called Value type". In other words "All C# - Dot net datatypes are Value types and memory allocated for value types is called Stack memory". When the program execution has finished all allocated space in Stack memory deallocated automatically. 

In my next post I have explained What is Heap and Reference type?

Fundamentals of C# Dot Net Datatypes

Hi all,

Hope you have better knowledge about dot net framework on my previous post Understanding Dot Net Framework. Now I am going to explain C# dot net datatypes. Ok, before start I want to explain some fundamentals of data. Of course many of you already know, anyway lets start.

In the above picture computer memory represents "A" as eight bits, I mean one byte. We all know

8 bit = 1 byte

So in this way we can represents up to 

2⁸ =256 characters. 

Here range for the characters are 0 -255. In C# we have a datatype byte, it's stored exactly 0 to 255 characters. In other words It's represents ASCII.

OK, Now if we want to represents more than 256 characters, what do we do? For this C# provide another datatype char, it's takes two bytes to represents a character. When we use this char datatype, we can represents up to,

2¹⁶ =65536

Here range for the characters are 0-65535. In other words, char datatype represents UNICODE. Series of char datatypes is called string. So we can categorize our data into three categories,

1. Alphanumeric
2. Numeric
3. Others

byte, char, string datatypes are represents Alphanumeric data. C# also having numeric datatypes. Lets we see what are all datatypes in c# using below diagram,

Below table represents min value and max value of each datatypes and what values it may have,

Category			Datatype	Range	Type of data
Alphanumeric			Byte	28 = 0 – 255	ASCII
			Char	216 = 0 – 65535	UNICODE
			String	Unlimited	Series of UNICODE
Numeric	Without Decimals	Signed numbers	Short / Int16	216 =  - 32768 to 32767	0 to 9
			Int / Int32	232	0 to 9
			Long/Int64	264	0 to 9
		Unsigned numbers	Ushort/ Uint16	216 = 0 to 65535	0 to 9
			Uint/Int32	232	0 to 9
			Ulong/Int64	264	0 to 9
	With Decimals		Float	Precision up to 7 decimals	0 to 9
			Double	Precision up to 16 decimals	0 to 9
			Decimal	Precision up to 32 decimals	0 to 9