I have written quite a number of console programs now and wondered at what point in learning C is it beneficial to begin to learn to make a GUI.

So far I have studied
Algorithms
Variables
Arithmetic Expressions
Input and Output
Program style
Conditionals
Functions
Function Parameters
Iteration
Loop Development / Program Schemes
Complex Conditionals
Functional / Data Decomposition
Function Design
Switch
Structures / Unions
Pointer Parameters
Arrays
Searching
Sorting
Multi-Dimensional Arrays
Strings
Nested Data Structures
Recursion
I am just beginning Memory management, Dynamic arrays etc..

Wow I didn't realize how big the list was.

Is it too soon to try this?? If not what would be the best course of action?? I am on Ubuntu and will most likely start with Glade Interface Designer (just cause it's already installed). I also have Window XP but almost never use it. Does anyone knows how to design for both?? I could use a heads up on what software works best.