Programming Languages

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Programming Languages

• From FORTRAN to WHYP

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A Brief History of Programming Languages
http//www.byte.com/art/9509/sec7/art19.htm
http//merd.net/pixel/language-study/diagram.html
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How would you have a computer evaluate this
expression?
X AB (C D)/(E F)
Reverse Polish Notation (RPN) Postfix ABCD-EF/
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Forth
http//www.ultratechnology.com/dindex.htm
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WHYP

• Pronounced whip
• Words to Help You Program
• Subroutine-threaded Forth for Embedded Systems
• 68HC11 (16-bit)
• 68332 (32-bit)
• 68HC12 (16-bit)

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WHYP is developed from scratch in the new
bookDesign of Embedded Systems Using 68HC12/11
MicrocontrollersbyRichard E. HaskellPrentice
Hall, 2000
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FORTH is a programming language that ---

• was invented by Charles Moore in the early 70s
• is extensible
• keeps all definitions in a dictionary
• is extremely compact
• is recursive
• can be programmed in RAM, PROM, or ROM
• is structured
• uses a stack and postfix notation

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Chuck Moore reading Haskells WHYP book
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WHYP Colon Definitions
squared ( n -- n2) DUP cubed ( n
-- n3) DUP \ n n squared \ n
n2 \ n3
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Branching and Looping in WHYP

• IFELSETHEN
• FORNEXT
• BEGINAGAIN
• BEGINUNTIL
• BEGINWHILEREPEAT

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IFELSETHEN
ltcondgt IF lttrue statementsgt ELSE ltfalse
statementsgt THEN
ltcondgt is either TRUE (-1) or FALSE (0)
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WHYP Conditional Words
lt ( n1 n2 -- f ) (less-than) gt ( n1 n2 -- f
) (greater-than) ( n1 n2 -- f
) (equals) ltgt ( n1 n2 -- f ) (not-equals) lt (
n1 n2 -- f ) (less-than or equal) gt ( n1 n2
-- f ) (greater-than or equal) 0lt ( n --
f) (zero-less) 0gt ( n -- f) (zero-greater) 0
( n -- f) (zero-equal) Ult ( u1 u2 -- f
) (U-less-than) Ugt ( u1 u2 -- f
) (U-greater-than) Ult ( u1 u2 -- f
) (U-less-than or equal) Ugt ( u1 u2 -- f
) (U-greater-than or equal)
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(No Transcript)
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FORNEXT Loop
n FOR ltWHYP statementsgt NEXT
gtR
drjne ltWHYP statementsgt
Decrement top of return stack and branch back to
ltWHYP statementsgt if not equal to
zero. Therefore, ltWHYP statementsgt are executed n
times.
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BEGINAGAIN
BEGIN ltWHYP statementsgt AGAIN
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BEGINUNTIL
BEGIN ltWHYP statementsgt ltflaggt UNTIL
ltflaggt is either TRUE or FALSE usually from some
WHYP conditional word
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BEGINWHILEREPEAT
BEGIN ltwordsgt ltflaggt WHILE ltwordsgt REPEAT