Hi this question is very broad. 

SCENARIO --
I want to diagrammatically represent the functions of my class and how they call each other? The functions have a definite pattern and I want to do this to accommodate future changes such as adding a new functionality which will require to write a new function. 

Eg:

function\_1() ---> calls function\_master()

function\_2() ---> calls function\_master()

If tomorrow function\_3 is created then the makers should know that they need to make a call to function\_master(). 

There are many such complex relationships.

The Real Question --> What I'm trying to achieve, does it have a name? like function mapping diagram. 
I know about class diagrams. I don't want to include them. I want detailed diagram of only functions calling each other.

Can you suggest some tools so that I can make it?