Rules for constructing variable names are same for all the data types.
Related Read:
Rules for Constructing int, float, char constants: C
Rules for Constructing Variable Names: C
1. First character in a variable name must be an alphabet or an underscore( _ ).
2. Variable name can have alphabet, digits and underscore.
3. No commas, space allowed in variable name.
4. No other special symbols other than underscore is allowed.
5. C variables are case sensitive. Ex: name and Name are two different variables.
6. You can not use keywords / reserve words as variable name in C.
Valid Variable Names
_name
user_name
age20
iMac
Invalid Variable Names
9hundred
Micro soft
Apple$computers
Note: All these rules for constructing variable names apply for all the data types in C.