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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 = A*B + (C – D)/(E + F) Reverse Polish Notation (RPN) Postfix AB*CD-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 book: Design of Embedded Systems Using 68HC12/11 Microcontrollers by Richard E. Haskell Prentice Hall, 2000
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FORTH is a programming language that --- was invented by Charles Moore in the early 70’s 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 Haskell’s WHYP book
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WHYP Colon Definitions : squared( n -- n**2) DUP * ; : cubed( n -- n**3) DUP\ n n squared \ n n**2 * ;\ n**3
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Branching and Looping in WHYP IF…ELSE…THEN FOR…NEXT BEGIN…AGAIN BEGIN…UNTIL BEGIN…WHILE…REPEAT
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IF…ELSE…THEN IF ELSE THEN is either TRUE (-1) or FALSE (0)
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WHYP Conditional Words <( n1 n2 -- f )(“less-than”) >( n1 n2 -- f )(“greater-than”) =( n1 n2 -- f )(“equals”) <>( n1 n2 -- f )(“not-equals”) <=( n1 n2 -- f )(“less-than or equal”) >=( n1 n2 -- f )(“greater-than or equal”) 0<( n -- f)(“zero-less”) 0>( n -- f)(“zero-greater”) 0=( n -- f)(“zero-equal”) U<( u1 u2 -- f )(“U-less-than”) U>( u1 u2 -- f )(“U-greater-than”) U<=( u1 u2 -- f )(“U-less-than or equal”) U>=( u1 u2 -- f )(“U-greater-than or equal”)
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>R Decrement top of return stack and branch back to if not equal to zero. Therefore, are executed n times. FOR…NEXT Loop n FOR NEXT drjne
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BEGIN…AGAIN BEGIN AGAIN
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BEGIN…UNTIL BEGIN UNTIL is either TRUE or FALSE usually from some WHYP conditional word
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BEGIN…WHILE…REPEAT BEGIN WHILE REPEAT
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