Keeping track of variables.

[kingfool]

Is there an editor I can use that will help me find the first instance a 
variable was used across an entire program of multiple files? Reason I ask 
is because I'm going through and adding features to a program as a learning 
experience. Coming from C++ as my only programming language I find it a bit 
confusing to not know when something was declared/used first, which can 
reveal a bit more about what the variable is for.