Here's why:
* Readability: Starting a variable name with a number can make it harder for humans to read and understand the code. It can also be confusing to distinguish between a variable name and a numerical value.
* Parsing: Most languages have parsers that analyze code. Starting a variable name with a number can cause conflicts with how these parsers understand the syntax.
* Keywords: In many languages, numbers are reserved as keywords for special operations or data types.
Common Rules for Variable Names:
* Start with a letter or underscore: `_myVariable`, `myVariable` are valid.
* Use alphanumeric characters and underscores: `my_variable1`, `variable_2` are valid.
* Case-sensitive: `myVariable` is different from `MyVariable` in case-sensitive languages.
Exceptions:
There are some languages that allow numbers at the beginning of variable names. Some examples include:
* Python: While not generally recommended, Python allows you to start a variable name with a number. However, it's best practice to avoid this.
* MATLAB: MATLAB allows numbers at the beginning of variable names.
It's important to note: Even if a language allows numbers at the beginning of variable names, it's generally considered poor coding practice. Following standard naming conventions makes your code more readable and maintainable.