Comments

c This is a comment

Strings, numbers and characters

"'this' is a string"
'and so is "this"'
U+0041 d65 x41   c these are all the letter A

Prefixes and Virtual Keys

c Match RAlt+E on desktops, Ctrl+Alt+E on web because L/R Alt not consistently supported in browsers.
$KeymanOnly: + [RALT K_E] > "€"
$KeymanWeb: + [CTRL ALT K_E] > "€"

Example Code

c =====================Begin Identity Section===================================================
c 
c Mnemonic input method for Amharic script on US-QWERTY
c keyboards for Keyman version 7.1, compliant with Unicode 4.1 and later.
c 

store(&VERSION) '9.0'
store(&Name) "Amharic"
c store(&MnemonicLayout) "1"
store(&CapsAlwaysOff) "1"
store(&Copyright) "Creative Commons Attribution 3.0"
store(&Message) "This is an Amharic language mnemonic input method for Ethiopic script that requires Unicode 4.1 support."
store(&WINDOWSLANGUAGES) 'x045E x045E'
store(&LANGUAGE) 'x045E'
store(&EthnologueCode) "amh"
store(&VISUALKEYBOARD) 'gff-amh-7.kvk'
store(&KMW_EMBEDCSS) 'gff-amh-7.css'
HOTKEY "^%A"
c 
c =====================End Identity Section=====================================================

c =====================Begin Data Section=======================================================

c ---------------------Maps for Numbers---------------------------------------------------------
store(ArabOnes) '23456789'
store(ones)     '፪፫፬፭፮፯፰፱'
store(tens)     '፳፴፵፶፷፸፹፺'
store(arabNumbers) '123456789'
store(ethNumbers) '፩፪፫፬፭፮፯፰፱፲፳፴፵፶፷፸፹፺፻፼'
store(arabNumbersWithZero) '0123456789'
store(ColonOrComma) ':,'
store(ethWordspaceOrComma) '፡፣'
c ---------------------End Numbers--------------------------------------------------------------

c =====================End Data Section=========================================================

c =====================Begin Functional Section=================================================
c 
store(&LAYOUTFILE) 'gff-amh-7_layout.js'
store(&BITMAP) 'amharic.bmp'
store(&TARGETS) 'any windows'
begin Unicode > use(main)
group(main) using keys    

c ---------------------Input of Numbers---------------------------------------------------------

c Special Rule for Arabic Numerals
c 
c The following attempts to auto-correct the use of Ethiopic wordspace and
c Ethiopic comma within an Arabic numeral context.  Ethiopic wordspace gets
c used erroneously in time formats and Ethiopic commas as an order of thousands
c delimiter. The correction context is not known until numerals appear on _both_
c sides of the punctuation.
c 
  any(arabNumbersWithZero) any(ethWordspaceOrComma) + any(arabNumbers) > index(arabNumbersWithZero,1) index(ColonOrComma,2) index(arabNumbers,3)

c Ethiopic Numerals

  "'" + '1' > '፩'
  "'" + any(ArabOnes) > index(ones,2)

c special cases for multiples of one
  '፩'  + '0' > '፲'
  '፲'  + '0' > '፻'
  '፻'  + '0' > '፲፻'
  '፲፻' + '0' > '፼'
  '፼'  + '0' > '፲፼'    
  '፲፼' + '0' > '፻፼' 
  '፻፼'  + '0' > '፲፻፼'
  '፲፻፼' + '0' > '፼፼'
  '፼፼' + '0' > context beep  c do not go any higher, we could beep here

c upto the order of 100 million
  any(ones)     + '0' > index(tens,1)
  any(tens)     + '0' > index(ones,1) '፻'  c Hundreds
  any(ones)  '፻ '+ '0' > index(tens,1) '፻'  c Thousands
  any(tens)  '፻' + '0' > index(ones,1) '፼'  c Ten Thousands
  any(ones)  '፼' + '0' > index(tens,1) '፼'  c Hundred Thousands
  any(tens)  '፼' + '0' > index(ones,1) '፻፼' c Millions
  any(ones) '፻፼' + '0' > index(tens,1) '፻፼' c Ten Millions
  any(tens) '፻፼' + '0' > index(ones,1) '፼፼' c Hundred Millions

c enhance this later, look for something that can copy a match over
  any(ethNumbers) + any(arabNumbers) > index(ethNumbers,1)  index(ethNumbers,2)
c ---------------------End Input of Numbers-----------------------------------------------------
                                            
c =====================End Functional Section===================================================