Application Application as seen by the user. Application calls Each rectangle represents the invocation of a java method written by the application author(s). White links represents the way each method call sub methods. Application and libraries calls Each rectangle represents the invocation of a java method, in blue are methods of the application, whereas in green are methods from the library javafx (handling the graphical interface). White links represents the way each method call sub methods. Byte code The jvm (java virtual machine) doesn't read java code. Instead this code is transformed in a more compact form called bytecode. Each color segment represents a bytecode instruction. System calls Each square represent a system call. A system call is an operation handled by the operating system. x86 In order to executed by micro processor, a program must be converted in a serie of instructions that the processor understand. A common instruction set nodays is x86. Each color segment represents an x86 instruction.