diff --git a/requirements.txt b/requirements.txt
index c109b2627..22ff5ae30 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,3 @@
 attrs
 ply
 git+https://github.com/irmen/cbmcodecs.git@master
-
diff --git a/tinyvm/main.py b/tinyvm/main.py
index 1356437bf..267ef98d4 100644
--- a/tinyvm/main.py
+++ b/tinyvm/main.py
@@ -1,6 +1,12 @@
+"""
+Simplistic 8/16 bit Virtual Machine to execute a stack based instruction language.
+Main entry point to launch a VM to execute the given programs.
+
+Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0
+"""
+
 import sys
 from .parse import Parser
-# from .program import Program, Opcode, Block, Instruction
 from .vm import VM
 
 mainprogram = None
@@ -20,7 +26,7 @@ if len(sys.argv) not in (2, 3):
     raise SystemExit("provide 1 or 2 program file names as arguments")
 
 # zero page and hardware stack of a 6502 cpu are off limits for now
-VM.readonly_mem_ranges = [(0x00, 0xff), (0x100, 0x1ff), (0xa000, 0xbfff), (0xe000, 0xffff)]
+VM.readonly_mem_ranges = [(0x00, 0xff), (0x100, 0x1ff)]
 vm = VM(mainprogram, timerprogram)
 vm.enable_charscreen(0x0400, 40, 25)
 vm.run()
diff --git a/tinyvm/parse.py b/tinyvm/parse.py
index f7ad545d1..179a07907 100644
--- a/tinyvm/parse.py
+++ b/tinyvm/parse.py
@@ -1,3 +1,10 @@
+"""
+Simplistic 8/16 bit Virtual Machine to execute a stack based instruction language.
+Parser for the simplistic text based program representation
+
+Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0
+"""
+
 import array
 from typing import Optional, List, Tuple, Dict, Any
 from .program import DataType, Opcode, Program, Block, Variable, Instruction, Value
diff --git a/tinyvm/program.py b/tinyvm/program.py
index aa948e1a2..2b6090111 100644
--- a/tinyvm/program.py
+++ b/tinyvm/program.py
@@ -1,3 +1,10 @@
+"""
+Simplistic 8/16 bit Virtual Machine to execute a stack based instruction language.
+These are the program/instruction definitions that make up a program for the vm
+
+Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0
+"""
+
 import enum
 import array
 import operator
diff --git a/tinyvm/vm.py b/tinyvm/vm.py
index ff62bd470..ee887dbfb 100644
--- a/tinyvm/vm.py
+++ b/tinyvm/vm.py
@@ -1,3 +1,10 @@
+"""
+Simplistic 8/16 bit Virtual Machine to execute a stack based instruction language.
+This is the VM itself (execution engine)
+
+Written by Irmen de Jong (irmen@razorvine.net) - license: GNU GPL 3.0
+"""
+
 # 8/16 bit virtual machine
 
 # machine specs: