An Introduction to C & GUI ProgrammingFrom https://www.raspberrypi.org/magpi/issues/c-gui-programming/Even if you are an absolute beginner, this book will teach you all you need to know to write simple programs in C and start creating GUIs.The first half of the book is an introduction to C, and covers the basics of writing simple command-line programs. The second half shows how to use the GTK user interface toolkit with C to create feature-rich GUI applications which can be run on the desktop.156 pages of essential information:Create simple command-line C programsControl flow with conditions and loopsHandle variables, strings, and filesDesign graphical user interface applications in CHandle user input with buttons and menusUse advanced UI features such as data stores and dialogs