Rules for declaring variable

To declare any variable in C language one must follow certain rules like:

1. One must not use spaces in declaration of variables.
2. Every variable should start from alphabet or underscore(_)
3. Except underscore(_) no special characters is allowed.
4. Variable must be at left side of assignment operator(=)
5. No keyword must be declared as variable. For more information on keywords click here.

Examples of valid variables are:
int a= 2
float m =2.97

Examples of invalid variables are:

Variable name	Reason for being invalid
int float = 2	float is keyword
int new number=89	Space not allowed
float variable&answer	No Special characters except underscore(_)