Yet another documentation update

Author: AtomicScience

doc/About JavOC/Changelog and to-do.md

@@ -13,13 +13,10 @@ In this pre-release I plan to implement readings of the constant pool and expand
   - [x] Access flags
   - [x] Constant pool
 ### Documentation
-- [ ] Class Loading algorithm:
-  - [ ] Constant pool loading procedure
-  - [ ] Descriptors
-- [ ] Expand "Class File Format"
-  - [ ] 'Magic Value'
-  - [ ] Versions
-  - [ ] Constant pool
+- [x] Expand "Class File Format"
+  - [x] 'Magic Value'
+  - [x] Versions
+  - [x] Constant pool
 - [ ] Expand "Class structure by example"
   - [ ] 'Magic value'
   - [ ] Versions

doc/Class Loading and structure/Constant pool.md

@@ -1,4 +1,24 @@
 # Constant pool
-Constant pool in Java class is a structure, that contains, well, *constants*. 
+## Purpose of constant pool
+Bytecode uses data very often, and something like string literals cannot be stored into code, but instead it should be kept *somewhere* to be later referenced by bytecode:
 
-However, 
+```java
+    new #2 		    // Class java/lang/Object
+```
+
+This data will never change during runtime, thus making these values **constants**! And these values are stored in a special structure called **constant pool**
+
+## Structrue of constant pool
+That's how it looks:
+
+<img src="../Diagrams/Class%20Loading%20and%20structure/Constant%20Pool.png" alt="drawing" width="90%"/>
+
+The very first field of it is a `Constant pool size` - a field that, suddenly, defines the size of the constant pool, but, for some mysterious reason, it's actually *greater* than amount of constants by 1 *(So that if `constant pool size` has a value of 5, there are actually only 4 constants in the pool)*
+
+As you can see, the actual length of the constant pool is unknown *(marked as X)*. That's because each constant entry has its own length - for example, `Utf8` constant may be 20 bytes long, or 200 bytes - we won't know it until we start reading constant pool values, one by one.
+
+## Constant in constant pool
+There are actually many different constants that define different things - from float and double variables to method and class signatures.
+
+In Java 6, that JavOC implements, there are 11 different constants, that I'm too lazy to describe, so you better look them up in official documentation:
+[Here it goes](https://docs.oracle.com/javase/specs/jvms/se6/html/ClassFile.doc.html#20080)