Final answer:
In programming, variable names can usually include letters, numbers, and the underscore symbol (_), but must start with a letter or an underscore. Other symbols and punctuation marks are generally not allowed as they can cause errors or be misinterpreted.
Step-by-step explanation:
When discussing variable names in the context of programming, the symbols that can be included within a variable name are typically limited to alphanumeric characters (letters and numbers) and the underscore symbol (_). In most programming languages, variable names must start with a letter or an underscore, not a number. The use of other symbols, such as special characters or punctuation, is generally not allowed as they could be interpreted as operators or could cause syntax errors.
For example, 'variable1' and 'user_name' are valid variable names, whereas 'variable!' or '3example' are not. The key is consistency; if you create a variable named 'height_meter', you should consistently use this name throughout your code to refer to that variable.
It's important to remember that these are just conventions for most programming languages, and the specific rules can vary between different languages.