Final changes in "Class File Format" before 0.2

Author: AtomicScience

doc/Class Loading and structure/Class File Format.md

@@ -24,7 +24,12 @@ According to the [official JVM Specifications](https://docs.oracle.com/javase/sp
 
 Looks complicated... But here is the pretty diagram, that explains everything!
 
-<img src="../Diagrams/Class%20Loading%20and%20structure/Class%20File%20Structure.drawio.svg" alt="drawing" width="100%"/>
+<details style="background-color:#F6F6F6">
+<p style="background-color:#F6F6F6">
+<summary>Diagram</summary>
+<img style="background-color:#F6F6F6" src="../Diagrams/Class%20Loading%20and%20structure/Class%20File%20Structure.drawio.svg" width="100%"/>
+</p>
+</details>
 
 Still complicated, of course. But at least it is much more convenient to work with, right?
 ## Detailed fields description
@@ -34,5 +39,24 @@ Let's start describing each field, one by one:
 <img align="right" src="../Diagrams/Class%20Loading%20and%20structure/Magic%20Value.png" alt="drawing" width="100"/>
 
 ### Magic value
-Each `.class` value starts with special 'magic value' - a sequence of 4 bytes, that all Java class start with. It's value is 0xCAFEBABE 
-</p>
+Each `.class` value starts with special 'magic value' - a sequence of 4 bytes, that all Java class start with. Its value is 0xCAFEBABE 
+</p>
+
+### Minor and major versions
+<img align="right" src="../Diagrams/Class%20Loading%20and%20structure/Versions.png" alt="drawing" width="200"/>
+Each class was compiled to be used with a specific version of Java. It was quite complex back in old versions of Java, but today everything is pretty straightforward - JVM can run classes of its version and classes with *older* versions. In other words, JVMs are **backwards compatible**
+
+To store version of the Java that compiled the file, Major and Minor fields exist
+
+Each major release of Java is assigned to its *major version*. For example, Java 6, that JavOC is intended to implement, has major version of `50`.
+
+Minor version, however, is just a legacy field, that does not mean anything -  any JVM should be able to run any minor version, if it supports the major. For example, Java 6 should be able to run `50.0`, `50.1`, `50.255` or any other. 
+
+Modern compilers set this field to 0
+
+### Constant pool
+
+<img align="right" src="../Diagrams/Class%20Loading%20and%20structure/Constant%20Pool.png" alt="drawing" width="400"/>
+This data structure is very complex, so there is a dedicated article about it: 
+
+[Constant Pool](Constant%20pool.md)