The cs2 VM is a stack machine which uses supports three primitive types (int,long,string). All types can be represtend by one of those three. The VM keeps a seperate stack for each of these primitives.

The stacks

There are tree stacks (int,long,string).
You can only access to last pushed value per stack
However the VM does not enforce ordered access so eg: pushint->pushstring->popint->popstring would be valid
- The Jagex cs2 compiler generally avoids this, but it can happen for script calls
The total stack size for each stack is limited to 1000 entries
There seems to be no hardcoded string length limit

Scripts calls

Functions get their own set of local variables (similar to registers), the number of vars is declared in the script metadata
When a script is called its arguments will be popped from stack and placed in the corresponding local variable slots.
Callees do not get an isolated stack. It is possible (but highly discouraged) to pop values from stack that weren't defined as script argument.
The stack is not used to store local variables when calling another script.
- presumably this means that there is a seperate recursion limit caused by some sort of "local variable stack"

Branching

The max script length seems to be 65535 ops. After that weird stuff starts happening
All jumps are relative. (relative to index + 1)
When none of the switch branches match the VM will simply go to the next instruction
Switch statements can only jump forward
All other branching ops can go back and forward

Arrays

Arrays are weird