diff --git a/builtins.simple b/builtins.simple
index 0d2b41e..df7c3ae 100644
--- a/builtins.simple
+++ b/builtins.simple
@@ -34,6 +34,8 @@ object inttrait:
 
     def tobool:
         self $int_tobool
+    def tostr:
+        self $int_tostr
 
 # Project: Boolean
 object booltrait:
@@ -46,3 +48,21 @@ object booltrait:
 
     def toint:
         self $bool_toint
+    def tostr:
+        self $bool_tostr
+
+# Project: String
+object strtrait:
+    def eq(other):
+        self $str_eq(other)
+    def add(other):
+        self $str_add(other)
+    def rev:
+        self $str_rev
+    def len:
+        self $str_len
+
+    def tobool:
+        self $str_tobool
+    def toint:
+        self $str_toint
diff --git a/de.churl.simple/bytecodeinterpreter.py b/de.churl.simple/bytecodeinterpreter.py
index 5f7d6fb..4f9b128 100644
--- a/de.churl.simple/bytecodeinterpreter.py
+++ b/de.churl.simple/bytecodeinterpreter.py
@@ -20,10 +20,11 @@ class Interpreter(object):
         return self.run(code, w_context)
 
     def read4(self, code, pc):
-        highval = ord(code[pc + 3])
-        if highval >= 128:
+        """ Converts 4 unicode characters to single 4 byte value """
+        highval = ord(code[pc + 3])  # most significant byte
+        if highval >= 128:  # convert from 2's complement?
             highval -= 256
-        return (ord(code[pc]) |
+        return (ord(code[pc]) |  # merge single bytes into 4 byte value
                 (ord(code[pc + 1]) << 8) |
                 (ord(code[pc + 2]) << 16) |
                 (highval << 24))
@@ -34,7 +35,7 @@ class Interpreter(object):
         code = bytecode.code
         print(disassemble(bytecode))
         while pc < len(code):
-            opcode = ord(code[pc])
+            opcode = ord(code[pc])  # convert unicode to number
             pc += 1
             if compile.isjump(opcode):
                 oparg = self.read4(code, pc)
@@ -67,6 +68,10 @@ class Interpreter(object):
                 elif opcode == compile.BOOL_LITERAL:  # Project: Boolean
                     w_value = self.space.newbool(oparg)  # oparg is 1 or 0
                     stack.append(w_value)
+                elif opcode == compile.STRING_LITERAL:  # Project: String
+                    value = bytecode.symbols[oparg]
+                    w_value = self.space.newstring(value)
+                    stack.append(w_value)
                 elif opcode == compile.MAKE_FUNCTION:
                     bc = bytecode.subbytecodes[oparg]
                     w_method = self.space.definemethod(name=bc.name, code=bc, w_target=w_context)
diff --git a/de.churl.simple/compile.py b/de.churl.simple/compile.py
index 025d40b..4f03bcd 100644
--- a/de.churl.simple/compile.py
+++ b/de.churl.simple/compile.py
@@ -111,6 +111,7 @@ import simpleast
 
 BOOL_LITERAL = 1  # 1 or 0 # Project: Boolean
 INT_LITERAL = 2  # integer value
+STRING_LITERAL = 3  # Project: String
 ASSIGNMENT = 4  # index of attrname
 METHOD_LOOKUP = 5  # index of method name
 METHOD_CALL = 6  # number of arguments
@@ -190,6 +191,7 @@ def compile(ast, argumentnames=[], name=None):
 
 stack_effects = {
     BOOL_LITERAL: 1,  # Project: Boolean
+    STRING_LITERAL: 1,  # Project: String
     INT_LITERAL: 1,
     ASSIGNMENT: -1,
     METHOD_LOOKUP: 1,
@@ -240,11 +242,11 @@ class Compiler(object):
                 self.code.append(c)
         elif hasarg(opcode):
             assert isinstance(arg, int)
-            if -127 <= arg <= 127:
-                self.code.append(chr(arg & 0xFF))
+            if -127 <= arg <= 127:  # arg can be encoded as one byte
+                self.code.append(chr(arg & 0xFF))  # mask the least significant byte and convert to unicode
             else:
-                self.code.append(chr(128))
-                for c in self.encode4(arg):
+                self.code.append(chr(128))  # padding character
+                for c in self.encode4(arg):  # append as 4 single bytes
                     self.code.append(c)
         else:
             assert arg is None
@@ -266,14 +268,17 @@ class Compiler(object):
             i += 1
 
     def encode4(self, value):
+        """ Encodes 4 byte value as list of 4 unicode characters. """
         return [chr(value & 0xFF),
                 chr((value >> 8) & 0xFF),
                 chr((value >> 16) & 0xFF),
                 chr((value >> 24) & 0xFF)]
 
     def lookup_symbol(self, symbol):
+        """ Assigns indices to symbols/strings """
         if symbol not in self.symbols:
             self.symbols[symbol] = len(self.symbols)
+
         return self.symbols[symbol]
 
     def compile(self, ast, needsresult=True):
@@ -286,6 +291,10 @@ class Compiler(object):
     def compile_BooleanLiteral(self, astnode, needsresult):
         self.emit(BOOL_LITERAL, astnode.value)
 
+    # Project: String
+    def compile_StringLiteral(self, astnode, needsresult):
+        self.emit(STRING_LITERAL, self.lookup_symbol(astnode.value))  # save string value to symboltable
+
     def compile_ImplicitSelf(self, astnode, needsresult):
         self.emit(IMPLICIT_SELF)
 
diff --git a/de.churl.simple/disass.py b/de.churl.simple/disass.py
index 1dc6129..f7cd9c4 100644
--- a/de.churl.simple/disass.py
+++ b/de.churl.simple/disass.py
@@ -1,5 +1,6 @@
 import compile
 
+
 def disassemble(bytecode, indent='', pc=-1):
     """ disassemble a bytecode object and print a readabable version of it"""
     assert isinstance(bytecode, compile.Bytecode)
@@ -18,12 +19,13 @@ for name, value in list(compile.__dict__.items()):
 class AbstractDisassembler(object):
 
     def read4(self, code, pc):
-        highval = ord(code[pc+3])
+        """ Converts 4 unicode characters to single 4 byte value """
+        highval = ord(code[pc + 3])
         if highval >= 128:
             highval -= 256
         return (ord(code[pc]) |
-                (ord(code[pc+1]) << 8) |
-                (ord(code[pc+2]) << 16) |
+                (ord(code[pc + 1]) << 8) |
+                (ord(code[pc + 2]) << 16) |
                 (highval << 24))
 
     def disassemble(self, bytecode, currpc=-1):
@@ -114,5 +116,3 @@ class Disassembler(AbstractDisassembler):
             print()
         else:
             print('\t', oparg)
-
-
diff --git a/de.churl.simple/objmodel.py b/de.churl.simple/objmodel.py
index a3e54f1..2c23865 100644
--- a/de.churl.simple/objmodel.py
+++ b/de.churl.simple/objmodel.py
@@ -77,7 +77,7 @@ class W_Integer(AbstractObject):
     def __init__(self, value, space=None, trait="inttrait"):
         self.value = int(value)
         self.space = space
-        self.__trait = trait  # used this to extend from W_Integer
+        self.__trait = trait  # able to extend from W_Integer
 
     def getparents(self):
         if self.space is None:
@@ -103,6 +103,37 @@ class W_Boolean(W_Integer):  # don't know if extending is good idea
     def __init__(self, value, space=None):
         super().__init__(int(value), space=space, trait="booltrait")
 
+    def __str__(self):
+        return str(bool(self.value))
+
+    __repr__ = __str__
+
+
+# Project: String
+class W_String(AbstractObject):
+    def __init__(self, value, space=None):
+        self.value = str(value)
+        self.space = space
+        self.__trait = "strtrait"
+
+    def getparents(self):
+        if self.space is None:
+            return []  # for tests
+        trait = self.space.getbuiltin(self.__trait)
+        assert trait is not None, 'O_o bogus state'
+        return [trait]
+
+    def hasslot(self, name):
+        return False
+
+    def __str__(self):
+        return self.value
+
+    __repr__ = __str__
+
+    def istrue(self):
+        return self.value != ""
+
 
 class W_Method(W_NormalObject):
 
diff --git a/de.churl.simple/objspace.py b/de.churl.simple/objspace.py
index e1a9758..c03a446 100644
--- a/de.churl.simple/objspace.py
+++ b/de.churl.simple/objspace.py
@@ -1,4 +1,4 @@
-from objmodel import W_Integer, W_Boolean
+from objmodel import W_Integer, W_Boolean, W_String
 from objmodel import W_Method
 from objmodel import W_NormalObject
 
@@ -53,6 +53,10 @@ class ObjectSpace(object):
     def newbool(self, value):
         return W_Boolean(value, space=self)
 
+    # Project: String
+    def newstring(self, value):
+        return W_String(value, space=self)
+
     def definemethod(self, name, code, w_target):
         w_meth = W_Method(code, name=name,
                           slots={'__parent__': w_target},
diff --git a/de.churl.simple/primitives.py b/de.churl.simple/primitives.py
index 7db12cd..fc7c3c0 100644
--- a/de.churl.simple/primitives.py
+++ b/de.churl.simple/primitives.py
@@ -19,7 +19,9 @@ def primitive(name, unwrap_spec, wrap_spec):  # decorator arguments
                 if t is int:
                     unwrapped_args += (arg.value,)
                 elif t is bool:  # Project: Boolean
-                    unwrapped_args += (bool(arg.value),)  # isn't necessary because "1 or 0" is valid
+                    unwrapped_args += (bool(arg.value),)  # isn't really necessary because "1 or 0" is also valid
+                elif t is str:  # Project: String
+                    unwrapped_args += (arg.value,)
                 else:
                     unwrapped_args += (arg,)
 
@@ -29,6 +31,8 @@ def primitive(name, unwrap_spec, wrap_spec):  # decorator arguments
                 return space.newint(result)
             elif wrap_spec is bool:  # Project: Boolean
                 return space.newbool(result)
+            elif wrap_spec is str:  # Project: String
+                return space.newstring(result)
             return result
 
         unwrapper.__qualname__ = name
@@ -78,6 +82,17 @@ def simple_int_increment(a):
     return a + 1
 
 
+# Project: Boolean, String, Double
+@primitive("int_tobool", [int], bool)
+def simple_int_tobool(a):
+    return a
+
+
+@primitive("int_tostr", [int], str)
+def simple_int_tobstr(a):
+    return a
+
+
 # Project: Boolean
 @primitive("bool_and", [bool, bool], bool)
 def simple_bool_and(a, b):
@@ -94,6 +109,17 @@ def simple_bool_not(a):
     return not a
 
 
+@primitive("bool_toint", [bool], int)
+def simple_bool_toint(a):
+    return a
+
+
+@primitive("bool_tostr", [bool], str)
+def simple_bool_tostr(a):
+    return str(a).lower()
+
+
+# bool stuff for int
 @primitive("int_eq", [int, int], bool)
 def simple_int_eq(a, b):
     return a == b
@@ -119,11 +145,32 @@ def simple_int_less(a, b):
     return a < b
 
 
-@primitive("int_tobool", [int], bool)
-def simple_int_tobool(a):
+# Project: String
+@primitive("str_eq", [str, str], bool)
+def simple_str_eq(a, b):
+    return a == b
+
+
+@primitive("str_add", [str, str], str)
+def simple_str_add(a, b):
+    return a + b
+
+
+@primitive("str_rev", [str], str)
+def simple_str_eq(a):
+    return a[::-1]
+
+
+@primitive("str_len", [str], int)
+def simple_str_eq(a):
+    return len(a)
+
+
+@primitive("str_toint", [str], int)
+def simple_str_toint(a):
     return a
 
 
-@primitive("bool_toint", [bool], int)
-def simple_bool_toint(a):
-    return a
+@primitive("str_tobool", [str], bool)
+def simple_str_tobool(a):
+    return a == "true"
diff --git a/de.churl.simple/simpleast.py b/de.churl.simple/simpleast.py
index d361fab..a7a79a7 100644
--- a/de.churl.simple/simpleast.py
+++ b/de.churl.simple/simpleast.py
@@ -93,16 +93,6 @@ class IntLiteral(Expression):
         self.value = int(value)
 
 
-# Project: String
-class StringLiteral(Expression):
-    """ A string literal (like "hello world") """
-
-    attrs = ["value"]
-
-    def __init__(self, value):
-        self.value = str(value)
-
-
 # Project: Boolean
 class BooleanLiteral(Expression):
     """ A boolean literal (like "false") """
@@ -113,6 +103,16 @@ class BooleanLiteral(Expression):
         self.value = value == "true"
 
 
+# Project: String
+class StringLiteral(Expression):
+    """ A string literal (like "hello world") """
+
+    attrs = ["value"]
+
+    def __init__(self, value):
+        self.value = str(value)
+
+
 class MethodCall(Expression):
     """ A call to a method with name 'methodname' on 'receiver' with
     'arguments' (which is a list of expression ASTs).
diff --git a/de.churl.simple/simplelexer.py b/de.churl.simple/simplelexer.py
index 3177219..9718494 100644
--- a/de.churl.simple/simplelexer.py
+++ b/de.churl.simple/simplelexer.py
@@ -1,4 +1,4 @@
-from rply import LexerGenerator
+from rply import LexerGenerator, LexingError
 from rply.token import Token
 
 # attempts at writing a simple Python-like lexer
@@ -90,7 +90,7 @@ def postprocess(tokens, source):
         elif token.name == "CloseBracket":
             parenthesis_level -= 1
             if parenthesis_level < 0:
-                raise LexerError(source, token.source_pos, "unmatched parenthesis")
+                raise LexingError("unmatched parenthesis", token.source_pos)
             output_tokens.append(token)
         elif token.name == "NewlineAndWhitespace":
             if i + 1 < len(tokens) and tokens[i + 1].name == "NewlineAndWhitespace":
@@ -182,8 +182,8 @@ While = r'while'
 Def = r'def'
 Object = r'object'
 
-tokens = ["If", "Else", "While", "Def", "Object", "Number", "String", "Ignore",
-          "Boolean",  # Project: Boolean
+tokens = ["If", "Else", "While", "Def", "Object", "Number", "Ignore",
+          "String", "Boolean",  # Project: Boolean, String
           "NewlineAndWhitespace", "OpenBracket", "CloseBracket", "Comma", "Assign", "Colon",
           "Increment", "Plus", "Minus", "Multiply", "Divide", "Modulo",  # Project: Sugar
           "Name", "PrimitiveName"]
diff --git a/de.churl.simple/simpleparser.py b/de.churl.simple/simpleparser.py
index b1998f0..29fdc84 100644
--- a/de.churl.simple/simpleparser.py
+++ b/de.churl.simple/simpleparser.py
@@ -6,10 +6,10 @@ from simplelexer import lex
 import simpleast
 
 pg = ParserGenerator(["If", "Else", "While", "Def", "Object", "Number",
-                      "Boolean",  # New Types
-                      "String", "Name", "Indent", "Dedent", "Newline", "OpenBracket",
+                      "String", "Boolean",  # Project: Boolean, String
+                      "Name", "Indent", "Dedent", "Newline", "OpenBracket",
                       "CloseBracket", "Comma", "Assign", "Colon",
-                      "Increment", "Plus", "Minus", "Multiply", "Divide", "Modulo",  # Sugar
+                      "Increment", "Plus", "Minus", "Multiply", "Divide", "Modulo",  # Project: Sugar
                       "PrimitiveName", "EOF"],
                      # Operator precedence for ambiguous rules, ascending
                      precedence=[("left", ["Plus", "Minus"]),
@@ -198,18 +198,18 @@ def number_expression(stmt):
     return simpleast.IntLiteral(stmt[0].value)
 
 
-# Project: String
-@pg.production("basic_expression : String")
-def string_expression(stmt):
-    return simpleast.StringLiteral(stmt[0].value[1:-1])  # cut off delimiters
-
-
 # Project: Boolean
 @pg.production("basic_expression : Boolean")
 def boolean_expression(stmt):
     return simpleast.BooleanLiteral(stmt[0].value)
 
 
+# Project: String
+@pg.production("basic_expression : String")
+def string_expression(stmt):
+    return simpleast.StringLiteral(stmt[0].value[1:-1])  # cut off delimiters
+
+
 @pg.production("basic_expression : implicitselfmethodcall")
 def implicitselfmethodcall(call):
     methodcall = call[0]
diff --git a/mytests/test_string.py b/mytests/test_string.py
index a3e6622..13dbd28 100644
--- a/mytests/test_string.py
+++ b/mytests/test_string.py
@@ -1,10 +1,24 @@
 import py
+from rply import Token
 
+from simpleast import Program, ExprStatement, BooleanLiteral, ImplicitSelf, Assignment, StringLiteral
+from simplelexer import lex
 from simpleparser import parse
-from objmodel import W_NormalObject, W_Integer
+from objmodel import W_NormalObject, W_Integer, W_String, W_Boolean
 from interpreter import Interpreter
 
 
+def test_basic_string_lexing():
+    assert lex("\"Hallo\"")[0] == Token("String", "\"Hallo\"")
+    assert lex("\'Hallo\'")[0] == Token("String", "\'Hallo\'")
+    assert lex("x = \"true\"")[:3] == [Token("Name", "x"), Token("Assign", "="), Token("String", "\"true\"")]
+
+
+def test_basic_string_parsing():
+    assert parse("\"false\"") == Program([ExprStatement(StringLiteral("false"))])
+    assert parse("x = \"false\"") == Program([Assignment(ImplicitSelf(), "x", StringLiteral("false"))])
+
+
 def test_string_assignment():
     ast = parse("""
 x = "Hallo"
@@ -19,6 +33,7 @@ x = "Hallo"
 
 def test_string_operations():
     ast = parse("""
+w = "Hallo" eq("Hallo")
 x = "Hallo" add("ollaH")
 y = "Hallo" rev
 z = "Hallo" len
@@ -27,9 +42,33 @@ z = "Hallo" len
     w_model = interpreter.make_module()
     interpreter.eval(ast, w_model)
 
+    assert isinstance(w_model.getvalue("w"), W_Boolean)
+    assert w_model.getvalue("w").istrue() is True
     assert isinstance(w_model.getvalue("x"), W_String)
     assert w_model.getvalue("x").value == "HalloollaH"
     assert isinstance(w_model.getvalue("y"), W_String)
     assert w_model.getvalue("y").value == "ollaH"
     assert isinstance(w_model.getvalue("z"), W_Integer)
     assert w_model.getvalue("z").value == 5
+
+
+def test_string_conversion():
+    ast = parse("""
+w = "true" tobool
+x = true tostr
+y = 25 tostr
+z = "25" toint
+""")
+
+    interpreter = Interpreter()
+    w_model = interpreter.make_module()
+    interpreter.eval(ast, w_model)
+
+    assert isinstance(w_model.getvalue("w"), W_Boolean)
+    assert w_model.getvalue("w").istrue() is True
+    assert isinstance(w_model.getvalue("x"), W_String)
+    assert w_model.getvalue("x").value == "true"
+    assert isinstance(w_model.getvalue("y"), W_String)
+    assert w_model.getvalue("y").value == "25"
+    assert isinstance(w_model.getvalue("z"), W_Integer)
+    assert w_model.getvalue("z").value == 25