diff --git a/inputbox.lua b/inputbox.lua
index 923194854..10e0c2467 100644
--- a/inputbox.lua
+++ b/inputbox.lua
@@ -6,7 +6,6 @@ require "graphics"
 ----------------------------------------------------
 -- General inputbox
 ----------------------------------------------------
-
 InputBox = {
 	-- Class vars:
 	h = 100,
@@ -25,9 +24,7 @@ InputBox = {
 	fheight = 25,
 	fwidth = 15,
 	commands = nil,
-	initialized = false,
-	
-	-- NuPogodi, 25.05.12: for full UTF8 support
+
 	vk_bg = 3,
 	charlist = {}, -- table to store input string
 	charpos = 1,
@@ -35,12 +32,13 @@ InputBox = {
 	-- values to control layouts: min & max
 	min_layout = 2,
 	max_layout = 9,
-	-- default layout = 2, i.e. shiftmode = symbolmode = utf8mode = false
-	layout = 2,
+	layout = 3,
 	-- now bits to toggle the layout mode
-	shiftmode = true,	-- toggle chars <> capitals,	lowest bit in (layout-2)
-	symbolmode = false,	-- toggle chars <> symbols,		middle bit in (layout-2)
-	utf8mode = false,	-- toggle english <> national,	highest bit in (layout-2)
+	shiftmode = true,	-- toggle chars <-> capitals,	lowest bit in (layout-2)
+	symbolmode = false,	-- toggle chars <-> symbols,	middle bit in (layout-2)
+	utf8mode = false,	-- toggle english <-> national,	highest bit in (layout-2)
+	calcmode = false,	-- toggle calculator mode
+	calcfunctions = nil, -- math functions for calculator helppage
 }
 
 function InputBox:new(o)
@@ -127,8 +125,13 @@ end
 ----------------------------------------------------------------------
 function InputBox:input(ypos, height, title, d_text, is_hint)
 	-- To avoid confusion with old ypos & height parameters, I'd better define
-	-- my own position, at the bottom screen edge (NuPogodi, 26.05.12)
+	-- my own position, at the bottom screen edge
 	ypos = fb.bb:getHeight() - 165
+	-- some corrections for calculator mode
+	if self.calcmode then
+		self:setCalcMode()
+	end
+
 	-- at first, draw titled box and content
 	local h, w = 55, fb.bb:getWidth() - 2
 	self:drawBox(ypos, w, h, title)
@@ -142,21 +145,16 @@ function InputBox:input(ypos, height, title, d_text, is_hint)
 		y_pos = ypos + 13,
 		h = 30,
 	}
+
 	if d_text then
 		if is_hint then
-		-- print hint text
+			-- print hint text
 			fb.bb:paintRect(self.input_start_x-5, self.input_start_y-19, self.input_slot_w, self.fheight, self.input_bg)
 			renderUtf8Text(fb.bb, self.input_start_x+5, self.input_start_y, self.face, d_text, 0)
 			fb.bb:dimRect(self.input_start_x-5, self.input_start_y-19, self.input_slot_w, self.fheight, self.input_bg)
 		else
-			self.input_string = d_text
-			string.gsub( d_text, "(.)", function(char)
-				table.insert(self.charlist, self.charpos, char)
-				self.charpos = self.charpos + 1
-				return ""
-			end)
-			Debug("charlist", self.charlist)
-
+			-- add text to input_string
+			self:StringToCharlist(d_text)
 			self.input_cur_x = self.input_cur_x + (self.fwidth * #self.charlist)
 			self.cursor.x_pos = self.cursor.x_pos + (self.fwidth * #self.charlist)
 			self:refreshText()
@@ -164,8 +162,10 @@ function InputBox:input(ypos, height, title, d_text, is_hint)
 	end
 	self.cursor:draw()
 	fb:refresh(1, 1, ypos, w, h)
+
+	local ev, keydef, command, ret_code
 	while true do
-		local ev = input.saveWaitForEvent()
+		ev = input.saveWaitForEvent()
 		ev.code = adjustKeyEvents(ev)
 		if ev.type == EV_KEY and ev.value ~= EVENT_VALUE_KEY_RELEASE then
 			keydef = Keydef:new(ev.code, getKeyModifier())
@@ -183,62 +183,63 @@ function InputBox:input(ypos, height, title, d_text, is_hint)
 			end
 		end -- if
 	end -- while
-	local return_str = self.input_string
+
+	local output = self.input_string
 	self.input_string = ""
 	self.charlist = {}
 	self.charpos = 1
-	return return_str
+	return output
 end
 
 function InputBox:setLayoutsTable()
-	-- trying to read the layout from the user-defined file "mykeyboard.lua"
-	local ok, stored = pcall(dofile,"./mykeyboard.lua")
+	-- trying to read the layout from the user-defined file
+	local ok, stored = pcall(dofile, lfs.currentdir() .. "/mykeyboard.lua")
 	if ok then
 		self.INPUT_KEYS = stored
 	else	-- if an error happens, we use the default layout
 		self.INPUT_KEYS = {
 			{ KEY_Q,	"Q",	"q",	"1",	"!",		"Я",	"я",	"1",	"!", },
 			{ KEY_W,	"W",	"w",	"2",	"?",		"Ж",	"ж",	"2",	"?", },
-			{ KEY_E,	"E",	"e",	"3",	"#",		"Е",	"е",	"3",	"«", },
-			{ KEY_R,	"R",	"r",	"4",	"@",		"Р",	"р",	"4",	"»", },
-			{ KEY_T,	"T",	"t",	"5",	"%",		"Т",	"т",	"5",	":", },
+			{ KEY_E,	"E",	"e",	"3",	"|",		"Е",	"е",	"3",	"«", },
+			{ KEY_R,	"R",	"r",	"4",	"#",		"Р",	"р",	"4",	"»", },
+			{ KEY_T,	"T",	"t",	"5",	"@",		"Т",	"т",	"5",	":", },
 			{ KEY_Y,	"Y",	"y",	"6",	"‰",		"Ы",	"ы",	"6",	";", },
-			{ KEY_U,	"U",	"u",	"7",	"\'",		"У",	"у",	"7",	"~", },
+			{ KEY_U,	"U",	"u",	"7",	"'",		"У",	"у",	"7",	"~", },
 			{ KEY_I,	"I",	"i",	"8",	"`",		"И",	"и",	"8",	"(",},
 			{ KEY_O,	"O",	"o",	"9",	":",		"О",	"о",	"9",	")",},
 			{ KEY_P,	"P",	"p",	"0",	";",		"П",	"п",	"0",	"=", },
 			-- middle raw
 			{ KEY_A,	"A",	"a",	"+",	"…",		"А",	"а",	"Ш",	"ш", },
 			{ KEY_S,	"S",	"s",	"-",	"_",		"С",	"с",	"Ѕ",	"ѕ", },
-			{ KEY_D,	"D",	"d",	"*",	"¦",		"Д",	"д",	"Э",	"э", },
-			{ KEY_F,	"F",	"f",	"/",	"|",		"Ф",	"ф",	"Ю",	"ю", },
-			{ KEY_G,	"G",	"g",	"\\",	"„",		"Г",	"г",	"Ґ",	"ґ", },
-			{ KEY_H,	"H",	"h",	"=",	"“",		"Ч",	"ч",	"Ј",	"ј", },
+			{ KEY_D,	"D",	"d",	"*",	"=",		"Д",	"д",	"Э",	"э", },
+			{ KEY_F,	"F",	"f",	"/",	"\\",		"Ф",	"ф",	"Ю",	"ю", },
+			{ KEY_G,	"G",	"g",	"%",	"„",		"Г",	"г",	"Ґ",	"ґ", },
+			{ KEY_H,	"H",	"h",	"^",	"“",		"Ч",	"ч",	"Ј",	"ј", },
 			{ KEY_J,	"J",	"j",	"<",	"”",		"Й",	"й",	"І",	"і", },
-			{ KEY_K,	"K",	"k",	"ˆ",	"\"",		"К",	"к",	"Ќ",	"ќ", },
+			{ KEY_K,	"K",	"k",	"=",	"\"",		"К",	"к",	"Ќ",	"ќ", },
 			{ KEY_L,	"L",	"l",	">",	"~",		"Л",	"л",	"Љ",	"љ", },
 			-- lowest raw
 			{ KEY_Z,	"Z",	"z",	"(",	"$",		"З",	"з",	"Щ",	"щ", },
 			{ KEY_X,	"X",	"x",	")",	"€",		"Х",	"х",	"№",	"@", },
-			{ KEY_C,	"C",	"c",	"{",	"¥",		"Ц",	"ц",	"Џ",	"џ", },
-			{ KEY_V,	"V",	"v",	"}",	"£",		"В",	"в",	"Ў",	"ў", },
-			{ KEY_B,	"B",	"b",	"[",	"‚",		"Б",	"б",	"Ћ",	"ћ", },
-			{ KEY_N,	"N",	"n",	"]",	"‘",		"Н",	"н",	"Њ",	"њ", },
-			{ KEY_M,	"M",	"m",	"&",	"’",		"М",	"м",	"Ї",	"ї", },
-			{ KEY_DOT,	".",	",",	".",	",",		".",	",",	"Є",	"є", },
+			{ KEY_C,	"C",	"c",	"&",	"¥",		"Ц",	"ц",	"Џ",	"џ", },
+			{ KEY_V,	"V",	"v",	":",	"£",		"В",	"в",	"Ў",	"ў", },
+			{ KEY_B,	"B",	"b",	"π",	"‚",		"Б",	"б",	"Ћ",	"ћ", },
+			{ KEY_N,	"N",	"n",	"е",	"‘",		"Н",	"н",	"Њ",	"њ", },
+			{ KEY_M,	"M",	"m",	"~",	"’",		"М",	"м",	"Ї",	"ї", },
+			{ KEY_DOT,	",",	".",	".",	",",		",",	".",	"Є",	"є", },
 			-- Let us make key 'Space' the same for all layouts
 			{ KEY_SPACE," ",	" ",	" ",	" ",		" ",	" ",	" ",	" ", },
-			-- Simultaneous pressing Alt + Q..P should also work properly
-			{ KEY_1,	"1",	" ",	" ",	" ",		"1",	" ",	" ",	" ", },
-			{ KEY_2,	"2",	" ",	" ",	" ",		"2",	" ",	" ",	" ", },
-			{ KEY_3,	"3",	" ",	" ",	" ",		"3",	" ",	" ",	" ", },
-			{ KEY_4,	"4",	" ",	" ",	" ",		"4",	" ",	" ",	" ", },
-			{ KEY_5,	"5",	" ",	" ",	" ",		"5",	" ",	" ",	" ", },
-			{ KEY_6,	"6",	" ",	" ",	" ",		"6",	" ",	" ",	" ", },
-			{ KEY_7,	"7",	" ",	" ",	" ",		"7",	" ",	" ",	" ", },
-			{ KEY_8,	"8",	" ",	" ",	" ",		"8",	" ",	" ",	" ", },
-			{ KEY_9,	"9",	" ",	" ",	" ",		"9",	" ",	" ",	" ", },
-			{ KEY_0,	"0",	" ",	" ",	" ",		"0",	" ",	" ",	" ", },
+			-- Simultaneous pressing Alt + Q..P should also work properly everywhere
+			{ KEY_1,	"1",	"1",	"1",	"1",		"1",	"1",	"1",	"1", },
+			{ KEY_2,	"2",	"2",	"2",	"2",		"2",	"2",	"2",	"2", },
+			{ KEY_3,	"3",	"3",	"3",	"3",		"3",	"3",	"3",	"3", },
+			{ KEY_4,	"4",	"4",	"4",	"4",		"4",	"4",	"4",	"4", },
+			{ KEY_5,	"5",	"5",	"5",	"5",		"5",	"5",	"5",	"5", },
+			{ KEY_6,	"6",	"6",	"6",	"6",		"6",	"6",	"6",	"6", },
+			{ KEY_7,	"7",	"7",	"7",	"7",		"7",	"7",	"7",	"7", },
+			{ KEY_8,	"8",	"8",	"8",	"8",		"8",	"8",	"8",	"8", },
+			{ KEY_9,	"9",	"9",	"9",	"9",		"9",	"9",	"9",	"9", },
+			{ KEY_0,	"0",	"0",	"0",	"0",		"0",	"0",	"0",	"0", },
 			-- DXG keys
 			{ KEY_SLASH,"/",	"\\",	"/",	"\\",		"/",	"\\",	"/",	"\\", },
 		}
@@ -281,13 +282,13 @@ function InputBox:DrawVirtualKeyboard()
 	blitbuffer.paintBorder(fb.bb, lx+9*dx-10, vy-dy-r-8, r, r, t, c, r)
 	renderUtf8Text(fb.bb, lx-5+9*dx, vy-dy-3, smfont, "Del", true)
 	-- Sym
-	blitbuffer.paintBorder(fb.bb, lx+8*dx-10, vy-r-8, r, r, t + (r-t)*number(self.symbolmode), c, r)
+	blitbuffer.paintBorder(fb.bb, lx+8*dx-10, vy-r-8, r, r, t + (r-t)*self:num(self.symbolmode), c, r)
 	renderUtf8Text(fb.bb, lx-5+8*dx, vy-3, smfont, "Sym", true)
 	-- Enter
 	blitbuffer.paintBorder(fb.bb, lx+9*dx-10, vy-r-8, r, r, t, c, r)
 	renderUtf8Text(fb.bb, lx+9*dx, vy-2, vkfont, "«", true)
 	-- Menu
-	blitbuffer.paintBorder(fb.bb, lx+10*dx-8, vy-2*dy-r-8, r+50, r, t+(r-t)*number(self.utf8mode), c, r)
+	blitbuffer.paintBorder(fb.bb, lx+10*dx-8, vy-2*dy-r-8, r+50, r, t+(r-t)*self:num(self.utf8mode), c, r)
 	renderUtf8Text(fb.bb, lx+10*dx+11, vy-2*dy-3, smfont, "Menu", true)
 	-- fiveway
 	local h=dy+2*r-2
@@ -296,6 +297,14 @@ function InputBox:DrawVirtualKeyboard()
 	fb:refresh(1, 1, fb.bb:getHeight()-120, fb.bb:getWidth()-2, 120)
 end
 
+function InputBox:num(bool)
+	return bool and 1 or 0
+end
+
+function InputBox:VKLayout(b1, b2, b3)
+	return 2 + self:num(b1) + 2 * self:num(b2) + 4 * self:num(b3)
+end
+
 function InputBox:addCharCommands(layout)
 	-- at first, let's define self.layout and extract separate bits as layout modes
 	if layout then
@@ -306,25 +315,48 @@ function InputBox:addCharCommands(layout)
 		-- fill the layout modes
 		layout = (layout - 2) % 4
 		self.shiftmode  = (layout == 1 or layout == 3)
-		self.symbolmode = (layout == 2 or layout == 3)
+		self.symbolmode = (layout == 2 or layout == 4)
 		self.utf8mode   = (self.layout > 5)
 	else	-- or, without input parameter, restore layout from current layout modes
-		self.layout = 2 + number(self.shiftmode) + 2 * number(self.symbolmode) + 4 * number(self.utf8mode)
+		self.layout = self:VKLayout(self.shiftmode, self.symbolmode, self.utf8mode)
 	end
+	-- let's define layout called by Shift+Key (to type capitalized chars being in low-case layout)
+	local shift_layout = self:VKLayout(not self.shiftmode, self.symbolmode, self.utf8mode)
 	-- adding the commands
 	for k,v in ipairs(self.INPUT_KEYS) do
-		-- seems to work without removing old commands,
-		self.commands:del(v[1], nil, "")
-		-- just redefining existing ones
-		self.commands:add(v[1], nil, "", "input "..v[self.layout],
+		-- just redefining existing
+		self.commands:add(v[1], nil, "A..Z", "enter character from virtual keyboard (VK)",
 			function(self)
 				self:addChar(v[self.layout])
 			end
 		)
+		-- and commands for chars pressed with Shift
+		self.commands:add(v[1], MOD_SHIFT, "A..Z", "enter capitalized VK-character",
+			function(self)
+				self:addChar(v[shift_layout])
+			end
+		)
 	end
 	self:DrawVirtualKeyboard()
 end
 
+function InputBox:StringToCharlist(text)
+	if text == nill then return end
+	-- clear
+	self.charlist = {}
+	self.charpos = 1
+	local prevcharcode, charcode = 0
+	for uchar in string.gfind(text, "([%z\1-\127\194-\244][\128-\191]*)") do
+		charcode = util.utf8charcode(uchar)
+		if prevcharcode then -- utf8
+			self.charlist[#self.charlist+1] = uchar
+		end
+		prevcharcode = charcode
+	end
+	self.input_string = self:CharlistToString()
+	self.charpos = #self.charlist+1
+end
+
 function InputBox:CharlistToString()
 	local s, i = ""
 	for i=1, #self.charlist do
@@ -333,22 +365,25 @@ function InputBox:CharlistToString()
 	return s
 end
 
-function number(bool)
-	return bool and 1 or 0
-end
-
 function InputBox:addAllCommands()
-	-- we only initialize once
+	-- if already initialized, we (re)define only calcmode-dependent commands
 	if self.commands then
+		self:ModeDependentCommands()
 		self:DrawVirtualKeyboard()
 		return
 	end
 	self:setLayoutsTable()
 	self.commands = Commands:new{}
-	-- adding command to enter character commands
-	self:addCharCommands()
+	-- adding character commands
+	self:addCharCommands(self.layout)
 	-- adding the rest commands (independent of the selected layout)
-	self.commands:add(KEY_FW_LEFT, nil, "",
+	self.commands:add(KEY_H, MOD_ALT, "H",
+		"show helppage",
+		function(self)
+			self:showHelpPage(self.commands)
+		end
+	)
+	self.commands:add(KEY_FW_LEFT, nil, "joypad left",
 		"move cursor left",
 		function(self)
 			if (self.cursor.x_pos + 3) > self.input_start_x then
@@ -358,7 +393,17 @@ function InputBox:addAllCommands()
 			end
 		end
 	)
-	self.commands:add(KEY_FW_RIGHT, nil, "",
+	self.commands:add(KEY_FW_LEFT, MOD_SHIFT, "left",
+		"move cursor to the first position",
+		function(self)
+			if (self.cursor.x_pos + 3) > self.input_start_x then
+				self.cursor:moveHorizontalAndDraw(-self.fwidth*(self.charpos-1))
+				self.charpos = 1
+				fb:refresh(1, self.input_start_x-5, self.ypos, self.input_slot_w, self.h)
+			end
+		end
+	)
+	self.commands:add(KEY_FW_RIGHT, nil, "joypad right",
 		"move cursor right",
 		function(self)
 			if (self.cursor.x_pos + 3) < self.input_cur_x then
@@ -368,75 +413,235 @@ function InputBox:addAllCommands()
 			end
 		end
 	)
-	self.commands:add({KEY_ENTER, KEY_FW_PRESS}, nil, "",
-		"submit input content",
+	self.commands:add(KEY_FW_RIGHT, MOD_SHIFT, "right",
+		"move cursor to the last position",
 		function(self)
-			if self.input_string == "" then
-				self.input_string = nil
+			if (self.cursor.x_pos + 3) < self.input_cur_x then
+				self.cursor:moveHorizontalAndDraw(self.fwidth*(#self.charlist+1-self.charpos))
+				self.charpos = #self.charlist + 1
+				fb:refresh(1, self.input_start_x-5, self.ypos, self.input_slot_w, self.h)
 			end
-			return "break"
 		end
 	)
-	self.commands:add(KEY_DEL, nil, "",
+	self.commands:add(KEY_DEL, nil, "Del",
 		"delete one character",
 		function(self)
 			self:delChar()
 		end
 	)
-	self.commands:add(KEY_DEL, MOD_SHIFT, "",
-		"empty inputbox",
+	self.commands:add(KEY_DEL, MOD_SHIFT, "Del",
+		"delete all characters (empty inputbox)",
 		function(self)
 			self:clearText()
 		end
 	)
-	self.commands:add({KEY_BACK, KEY_HOME}, nil, "",
-		"cancel inputbox",
+	self.commands:addGroup("up/down", { Keydef:new(KEY_FW_DOWN, nil), Keydef:new(KEY_FW_UP, nil) },
+		"goto previous/next VK-layout",
 		function(self)
-			self.input_string = nil
-			return "break"
-		end
-	)
-	self.commands:add(KEY_P, MOD_SHIFT, "P",
-		"make screenshot",
-		function(self)
-			Screen:screenshot()
-		end
-	)
-	self.commands:add(KEY_FW_DOWN, nil, "joypad down",
-		"goto next keyboard layout",
-		function(self)
-			if self.layout == self.max_layout then self:addCharCommands(self.min_layout)
-			else self:addCharCommands(self.layout+1) end
-		end
-	)
-	self.commands:add(KEY_FW_UP, nil, "joypad up",
-		"goto previous keyboard layout",
-		function(self)
-			if self.layout == self.min_layout then self:addCharCommands(self.max_layout)
-			else self:addCharCommands(self.layout-1) end
+			if keydef.keycode == KEY_FW_DOWN then
+				if self.layout == self.max_layout then self:addCharCommands(self.min_layout)
+				else self:addCharCommands(self.layout+1) end
+			else -- KEY_FW_UP
+				if self.layout == self.min_layout then self:addCharCommands(self.max_layout)
+				else self:addCharCommands(self.layout-1) end
+			end
+			
 		end
 	)
 	self.commands:add(KEY_AA, nil, "Aa",
-		"toggle layout: chars <> CHARS",
+		"toggle VK-layout: chars <> CHARS",
 		function(self)
 			self.shiftmode = not self.shiftmode
 			self:addCharCommands()
 		end
 	)
 	self.commands:add(KEY_SYM, nil, "Sym",
-		"toggle layout: chars <> symbols",
+		"toggle VK-layout: chars <> symbols",
 		function(self)
 			self.symbolmode = not self.symbolmode
 			self:addCharCommands()
 		end
 	)
 	self.commands:add(KEY_MENU, nil, "Menu",
-		"toggle layout: english <> national",
+		"toggle VK-layout: english <> national",
 		function(self)
 			self.utf8mode = not self.utf8mode
 			self:addCharCommands()
 		end
 	)
+	-- NuPogodi, 02.06.12: calcmode-dependent commands are collected
+	self:ModeDependentCommands() -- here
+
+	self.commands:add({KEY_BACK, KEY_HOME}, nil, "Back",
+		"back",
+		function(self)
+			self.input_string = nil
+			return "break"
+		end
+	)
+end
+-----------------------------------------------------------------
+-- NuPogodi, 02.06.12: Some Help- & Calculator-related functions
+-----------------------------------------------------------------
+function InputBox:defineCalcFunctions() -- for the calculator documentation
+	-- to initialize only once
+	if self.calcfunctions then return end
+
+	self.calcfunctions = Commands:new{}
+	-- remove initially added commands
+	self.calcfunctions:del(KEY_INTO_SCREEN_SAVER, nil, "Slider") 
+	self.calcfunctions:del(KEY_OUTOF_SCREEN_SAVER, nil, "Slider")
+	self.calcfunctions:del(KEY_CHARGING, nil, "plugin/out usb")
+	self.calcfunctions:del(KEY_NOT_CHARGING, nil, "plugin/out usb")
+	self.calcfunctions:del(KEY_SPACE, MOD_ALT, "Space")
+
+	local s = " " -- space for function groups
+	local a = 100 -- arithmetic functions
+	self.calcfunctions:add(a-1, nil,	s:rep(1),	string.upper("Ariphmetic operators"))
+	self.calcfunctions:add(a,   nil,	"+ -",		"addition: 1+2=3; substraction: 3-2=1")
+	self.calcfunctions:add(a+1, nil,	"* /",		"multiplication: 2*2=4; division: 4/2=2")
+	self.calcfunctions:add(a+3, nil,	"%",		"modulo (remainder): 5.2%2=1.2, π-π%0.01=3.14")
+	local r = 200 -- relations
+	self.calcfunctions:add(r-1, nil,	s:rep(2),	string.upper("Relational operators"))
+	self.calcfunctions:add(r,   nil,	"< >",		"less: (2<3)=true; more: (2>3)=false")
+	self.calcfunctions:add(r+1, nil,	"<=",		"less or equal: (3≤3)=true, (2≤1)=false")
+	self.calcfunctions:add(r+2, nil,	">=",		"more or equal: (3≥3)=true, (1≥2)=false")
+	self.calcfunctions:add(r+3, nil,	"==",		"equal: (3==3)=true, (1==2)=false")
+	self.calcfunctions:add(r+4, nil,	"~=",		"not equal: (6~=8)=true, (3~=3)=false")
+	local l = 300 -- logical
+	self.calcfunctions:add(l-1, nil,	s:rep(3),	string.upper("Logical operators"))
+	self.calcfunctions:add(l+0, nil,	"and, &",	"= logical 'and': (4 and 5)=5, (nil & 5)=nil")
+	self.calcfunctions:add(l+1, nil,	"or, |",	"= logical 'or': (4 or 5)=4, (false | 5)=5")
+	local c = 400 -- constants
+	self.calcfunctions:add(c-1, nil,	s:rep(4),	string.upper("Some constants"))
+	self.calcfunctions:add(c,   nil,	"pi, π",	"= 3.14159…; sin(π/2)=1, cos(π/2)=0")
+	self.calcfunctions:add(c+1, nil,	"е, exp(1)",	"= 2.71828…; log(е)=1")
+	local m = 500 -- mathematical
+	self.calcfunctions:add(m-1, nil,	s:rep(5),	string.upper("Mathematic functions"))
+	self.calcfunctions:add(m,   nil,	"abs(x)",	"absolute value of x: abs(1)=1, abs(-2)=2")
+	self.calcfunctions:add(m+1, nil,	"ceil(x)",	"round to integer no less than x: ceil(0.4)=1")
+	self.calcfunctions:add(m+2, nil,	"floor(x)",	"round to integer no greater than x: floor(0.4)=0")
+	self.calcfunctions:add(m+3, nil,	"^, pow(x,y)","= power: 2^10=1024, pow(4,0.5)=2")
+	self.calcfunctions:add(m+4, nil,	"exp(x), e^x","= exponent: exp(1)=2.71828…")
+	self.calcfunctions:add(m+5, nil,	"log(x)",	"the natural logarithm: log(e)=1")
+	self.calcfunctions:add(m+6, nil,	"log10(x)",	"the base 10 logarithm: log10(10)=1")
+	self.calcfunctions:add(m+7, nil,	"max(x,…)",	"return maximal value: max(0,-1,2,1)=2")
+	self.calcfunctions:add(m+8, nil,	"min(x,…)",	"return minimal value: min(0,-1,2,1)=-1")
+	self.calcfunctions:add(m+9, nil,	"sqrt(x)",	"return square root: sqrt(4)=2")
+	local t = 600 -- trigonometrical
+	self.calcfunctions:add(t,   nil,	s:rep(6),	string.upper("Trigonometric functions"))
+	self.calcfunctions:add(t+1, nil,	"deg(x)",	"convert radians to degrees: deg(π/2)=90")
+	self.calcfunctions:add(t+2, nil,	"rad(x)",	"convert degrees to radians: rad(180)=3.14159…")
+	self.calcfunctions:add(t+3, nil,	"sin(x)",	"sine for x given in radians: sin(π/2)=1")
+	self.calcfunctions:add(t+4, nil,	"cos(x)",	"cosine for x given in radians: cos(π)=-1")
+	self.calcfunctions:add(t+5, nil,	"tan(x)",	"tangent for x given in radians: tan(π/4)=1")
+	self.calcfunctions:add(t+6, nil,	"asin(x)",	"inverse sine (in radians): asin(1)/π=0.5")
+	self.calcfunctions:add(t+7, nil,	"acos(x)",	"inverse cosine (in radians): acos(0)/π=0.5")
+	self.calcfunctions:add(t+8, nil,	"atan(x)",	"inverse tangent (in radians): atan(1)/π=0.25")
+	self.calcfunctions:add(t+9, nil,	"atan2(x,y)",	"inverse tangent of two args: = atan(x/y)")
+	local h = 700 -- hyperbolical
+	self.calcfunctions:add(h,   nil,	s:rep(7),	string.upper("Hyperbolic functions"))
+	self.calcfunctions:add(h+1, nil,	"sinh(x)",	"hyperbolic sine, (exp(x)-exp(-x))/2")
+	self.calcfunctions:add(h+2, nil,	"cosh(x)",	"hyperbolic cosine, (exp(x)+exp(-x))/2")
+	self.calcfunctions:add(h+3, nil,	"tanh(x)",	"hyperbolic tangent, sinh(x)/cosh(x)")
+-- not yet documented > "fmod", "frexp", "huge", "ldexp", "modf", "randomseed", "random"
+end
+
+function InputBox:showHelpPage(list, title)
+	-- make inactive input slot
+	self.cursor:clear() -- hide cursor
+	fb.bb:dimRect(self.input_start_x-5, self.input_start_y-19, self.input_slot_w, self.fheight, self.input_bg)
+	fb:refresh(1, self.input_start_x-5, self.ypos, self.input_slot_w, self.h)
+	-- now start the helppage with own list of commands and own title
+	HelpPage:show(0, fb.bb:getHeight()-165, list, title)
+	-- on the helppage-exit, making inactive helpage
+	fb.bb:dimRect(0, 40, fb.bb:getWidth(), fb.bb:getHeight()-205, self.input_bg)
+	fb:refresh(1, 0, 40, fb.bb:getWidth(), fb.bb:getHeight()-205)
+	-- and active input slot
+	self:refreshText()
+	self.cursor:draw() -- show cursor = ready to input
+	fb:refresh(1, self.input_start_x-5, self.ypos, self.input_slot_w, self.h)
+end
+
+function InputBox:setCalcMode()
+	--clear previous input
+	self.input_string = ""
+	self.charlist = {}
+	self.charpos = 1
+	-- set proper layouts
+	self.layout = 4 -- digits
+	self.min_layout = 3
+	self.max_layout = 4
+end
+
+function InputBox:PrepareStringToCalc()
+	local s = string.lower(self.input_string)
+	-- continue interpreting the input
+	local mathe = {	"abs", "acos", "asin", "atan2", "atan", "ceil", "cosh", "cos",
+				"deg", "exp", "floor", "fmod", "frexp", "huge", "ldexp", "log10", "log",
+				"max", "min", "modf", "pi", "pow", "rad", "randomseed", "random",
+				"sinh", "sin", "sqrt", "tanh", "tan", }
+	-- to avoid any ambiguities (like sin & sinh), one has to replace by capitals
+	for i=1, #mathe do
+		s = string.gsub(s, mathe[i], string.upper("math."..mathe[i]))
+	end
+	-- some acronyms for constants & functions
+	s = string.gsub(s, "π", " math.pi ")
+	s = string.gsub(s, "е", " math.exp(1) ")
+	s = string.gsub(s, "&", " and ")
+	s = string.gsub(s, "|", " or ")
+	-- return the whole string in lowercase and eventually replace double "math."
+	return string.gsub(string.lower(s), "math.math.", "math.")
+end
+
+-- define whether we need to calculate the result or to return 'self.input_string'
+function InputBox:ModeDependentCommands()
+	if self.calcmode then
+		-- define what to do with the input_string
+		self.commands:add({KEY_FW_PRESS, KEY_ENTER}, nil, "joypad center",
+			"calculate the result",
+			function(self)
+				local s = self:PrepareStringToCalc()
+				if pcall(function () f = assert(loadstring("r = tostring("..s..")")) end) then
+					f()
+					self:clearText()
+					self.cursor:clear()
+					for i=1, string.len(r) do
+						table.insert(self.charlist, string.sub(r,i,i))
+					end
+					self.charpos = #self.charlist + 1
+					self.input_string = r
+					self:refreshText()
+					self.cursor:moveHorizontal(#self.charlist*self.fwidth)
+					self.cursor:draw()
+					fb:refresh(1, self.input_start_x-5, self.input_start_y-25, self.input_slot_w, self.h-25)
+				else
+					showInfoMsgWithDelay("Wrong Input! ", 2000, 1)
+				end -- if pcall
+			end -- function
+			)
+		-- add the calculator help (short list of available functions)
+		-- or, might be better, to make some help document and open it in reader ??
+		self.commands:add(KEY_M, MOD_ALT, "M",
+			"math functions available in calculator",
+			function(self)
+				self:defineCalcFunctions()
+				self:showHelpPage(self.calcfunctions, "Math Functions for Calculator")
+			end
+			)
+	else 	-- return input_string & close input box
+		self.commands:add({KEY_FW_PRESS, KEY_ENTER}, nil, "joypad center",
+			"submit input content",
+			function(self)
+				if self.input_string == "" then
+					self.input_string = nil
+				end
+				return "break"
+			end
+			)
+		-- delete calculator-specific help
+		self.commands:del(KEY_M, MOD_ALT, "M")
+	end -- if self.calcmode
 end
 
 ----------------------------------------------------
@@ -445,7 +650,6 @@ end
 ----------------------------------------------------
 
 NumInputBox = InputBox:new{
-	symbolmode = true,
 	layout = 4,
-	charlist = {}
+	charlist = {},
 }