It is 32 characters ideally but implementation specific.

In C, the maximum length of an identifier is implementation-defined, meaning it can vary depending on the compiler and system being used. However, most modern compilers support identifiers up to 31 or 63 characters long.

It’s important to note that even though a compiler might support identifiers of a certain length, it’s generally good practice to keep identifiers reasonably short and descriptive for code readability and maintainability. Using excessively long identifiers can make the code harder to read and understand.