I think I might have misunderstood what you mean, the reason for a function name to start with an "_" could be one of these: 1. the function is a system library level function 2. the function may be non-ANSI C compliant 3. it is just a naming convention, compiler specific 4. ...
1. the function is a system library level function
2. the function may be non-ANSI C compliant
3. it is just a naming convention, compiler specific
4. ...