C# Variable
What is Variable
Computer memory location has an address and holds a content. The address is a numerical number (often expressed in hexadecimal), which is hard for programmers to use directly. Typically, each address location holds 8-bit (i.e., 1-byte) of data. It is entirely up to the programmer to interpret the meaning of the data, such as integer, real number, characters or strings.
A variable is a name of memory location. It is used to store data of a particular type. Its value can be changed and it can be reused many times.
Instead of numerical addresses, names (or identifiers) are attached to certain addresses.
It is a way to represent memory location through symbol so that it can be easily identified.
![](https://i.ytimg.com/vi/tmgWKYBYf-o/maxresdefault.jpg)
![](https://media.geeksforgeeks.org/wp-content/uploads/20190708153106/Variables-in-C-1.jpg)
The following diagram illustrate the relationship between computers’ memory address and content; and variable’s name, type and value used by the programmers. The following diagram illustrate the relationship between computers’ memory address and content; and variable’s name, type and value used by the programmers.
![](https://www3.ntu.edu.sg/home/ehchua/programming/cpp/images/MemoryAddressContent.png)
Dynamic Memory Allocation are the most powerful features in C/C++ language, which allows programmers to directly manipulate memory to efficiently manage the memory – the most critical and scarce resource in computer – for best performance.
Basic Variable Type in C#
![](https://static.javatpoint.com/csharp/images/csharp-data-type1.png)
![](https://i0.wp.com/www.softwaretestingmaterial.com/wp-content/uploads/2018/03/Data-Types.png?resize=1297%2C748&ssl=1)
How to declare a variable
Let’s see the syntax to declare a variable:
variable_type variable_list;
The example of declaring variable is given below:
int i, j;
double d;
float f;
char ch;
Here, i, j, d, f, ch are variables and int, double, float, char are data types.
We can also provide values while declaring the variables as given below:
int i=2,j=4; //declaring 2 variable of integer type
float f=40.2;
char ch=’B’;
Rules for defining variables
A variable can have alphabets, digits and underscore.
A variable name can start with alphabet and underscore only. It can’t start with digit.
No white space is allowed within variable name.
A variable name must not be any reserved word or keyword e.g. char, float etc.
Valid variable names:
int x;
int _x;
int k20;
Invalid variable names:
int 4;
int x y;
int double;