diff --git a/README.md b/README.md
index 07099ae..677130e 100644
--- a/README.md
+++ b/README.md
@@ -145,4 +145,4 @@ end
 
 TODO:  
 * add string. instructions
-* add inc,dec,sub,div
+* metatable
diff --git a/faden.lua b/faden.lua
index 49d4a0e..3885844 100644
--- a/faden.lua
+++ b/faden.lua
@@ -85,7 +85,9 @@ return function(faden_manip, parsed)
 		try_rebirth = function(self)
 			if minetest.get_us_time() >= self.rebirth then
 				self:continue()
+				return true
 			end
+			return false
 		end,
 		exit = function(self)
 			self:flush()
diff --git a/standardbefehlssatz.lua b/standardbefehlssatz.lua
index dc5ce9b..3c609eb 100644
--- a/standardbefehlssatz.lua
+++ b/standardbefehlssatz.lua
@@ -9,6 +9,10 @@ s = {
 		return true, params[2]
 	end,
 
+	xchg = function(params)
+		return true, params[2], params[1]
+	end,
+
 	getvar = function(params, faden)
 		local p = params[1]
 		if type(p) ~= "string" then
@@ -29,7 +33,12 @@ s = {
 			return true, p1 + p2
 		end
 		if t1 == "boolean" then
-			return true, p1 and p2
+			for _,k in pairs(params) do
+				if k then
+					return true, true
+				end
+			end
+			return true, false
 		end
 		if t1 == "string" then
 			if #p1 + #p2 > faden.strlen_max then
@@ -40,6 +49,22 @@ s = {
 		return false, UAT
 	end,
 
+	sub = function(params)
+		local b = params[2]
+		b = b and tonumber(b)
+		local t2 = type(b)
+		if t2 ~= "number" then
+			return false, UAT
+		end
+		local t1 = type(params[1])
+		if t1 == "number" then
+			return true, params[1] - b
+		end
+		if t1 == "string" then
+			return true, params[1]:sub(b, params[3] and tonumber(params[3]))
+		end
+	end,
+
 	mul = function(params)
 		local p1,p2 = unpack(params)
 		local t1 = type(p1)
@@ -59,11 +84,39 @@ s = {
 			return true, p1 * p2
 		end
 		if t1 == "boolean" then
-			return true, p1 or p2
+			for _,k in pairs(params) do
+				if not k then
+					return true, false
+				end
+			end
+			return true, p1 and p2 -- nil is tested in the first two params
 		end
 		return false, UAT
 	end,
 
+	div = function(params)
+		local p1,p2 = unpack(params)
+		if type(p1) ~= "number"
+		or type(p2) ~= "number" then
+			return false, UAT
+		end
+		return true, p1 / p2
+	end,
+
+	inc = function(params)
+		if type(params[1]) ~= "number" then
+			return false, UAT
+		end
+		return true, params[1] + 1
+	end,
+
+	dec = function(params)
+		if type(params[1]) ~= "number" then
+			return false, UAT
+		end
+		return true, params[1] - 1
+	end,
+
 	neg = function(params)
 		local v = params[1]
 		local t = type(v)
@@ -74,7 +127,7 @@ s = {
 			return true, not v
 		end
 		if t == "string" then
-			return true, v:rev()
+			return true, v:rev() -- does string.rev exist?
 		end
 		return false, UAT
 	end,
@@ -190,6 +243,10 @@ s = {
 		return true, p1 < p2
 	end,
 
+	greater = function(params)
+		return s.less{params[2], params[1]}
+	end,
+
 	usleep = function(params, faden)
 		local p = params[1]
 		if type(p) ~= "number" then
@@ -217,7 +274,15 @@ s = {
 	end,
 
 	tostring = function(params)
-		return true, tostring(params[1])
+		return true, params[1] and tostring(params[1]) or nil
+	end,
+
+	tonumber = function(params)
+		return true, params[1] and tonumber(params[1])
+	end,
+
+	toboolean = function(params)
+		return true, params[1] and true or false
 	end,
 
 	print = function(params, faden)
@@ -259,4 +324,20 @@ for i = 1,#to_math_fcts do
 	end
 end
 
+local abbreviations = {
+	mov = ":=",
+	add = "+",
+	sub = "-",
+	mul = "*",
+	div = "/",
+	inc = "++",
+	dec = "--",
+	neg = "!",
+	less = "<",
+	equal = "==",
+	jmp = "@",
+	usleep = "...",
+}
+-- TODO set metatable
+
 return s
diff --git a/util/standartbefehlssatz_doc.lua b/util/standartbefehlssatz_doc.lua
index cfadaeb..5de9b8c 100644
--- a/util/standartbefehlssatz_doc.lua
+++ b/util/standartbefehlssatz_doc.lua
@@ -13,13 +13,19 @@ local types = {
 
 local instr = {
 	{"mov", "<v to>, <e from>", "Copies from into to."},
+	{"xchg", "<v a>, <v b>", "Switches a with b."},
 	{"getvar", "<vs varname>[, <ve exists>]", "Sets varname to the current variable called <varname> if it's set. If exists is passed, it's set to a bool indicating whether the variable was set."},
 	{"add", "<vn to>, <n from>", "to += from"},
-	{"add", "<vb to>, <b from>", "to = to and from"},
+	{"add", "<vb to>[, <b ba>[, <b bb>[…]]]", "to indicates whether at least one of the arguments is true"},
 	{"add", "<vs to>, <s from>", "to = to .. from"},
+	{"sub", "<vn num>, <n tosub>", "num -= tosub"},
+	{"sub", "<vs str>, <n start>[, <n end>]", "str = str:sub(start, end)"},
 	{"mul", "<vn to>, <n from>", "to *= from"},
-	{"mul", "<vb to>, <b from>", "to = to or from"},
+	{"mul", "<vb to>[, <b ba>[, <b bb>[…]]]", "to indicates whether all of the arguments are true"},
 	{"mul", "<vs str>, <n cnt>", "str = str:rep(from)"},
+	{"div", "<vn num>, <n todiv>", "num /= todiv"},
+	{"inc", "<vn num>", "++num"},
+	{"dec", "<vn num>", "--num"},
 	{"neg", "<vn num>", "num = -num"},
 	{"neg", "<vb var>", "var = not var"},
 	{"neg", "<vs str>", "str = str:rev()"},
@@ -33,10 +39,13 @@ local instr = {
 	{"equal", "<v a>, <e b>", "a = a == b"},
 	{"less", "<vn a>, <n b>", "a = a < b; after executing, a is a bool"},
 	{"less", "<vs a>, <s b>", "a = a < b; less also works for strings"},
+	{"greater", "<v a>, <e b>", "executes less b,a"},
 	{"usleep", "<n t>", "aborts the program for at least floor(max(0, t)) ms"},
 	{"sleep", "<n t>", "executes usleep with t * 1000000 as argument"},
 	{"get_us_time", "<v to>", "stores minetest.get_us_time() into to; can be used to measure time differences"},
 	{"tostring", "<ve var>", "var = tostring(var)"},
+	{"tonumber", "<ve var>", "var = tonumber(var)"},
+	{"toboolean", "<ve var>", "var = var and true or false"},
 	{"print", "<e a>[, <e b>[, <e c>[…]]]", "adds variables to the log, seperated by \\t, \\n is added at the end"},
 	{"flush", "", "Output the log, this should vary for every mod."},
 }