INTRODUCTION



computer. In fact, we don't really have to "invent" a way to solve these
problems; the solutions are within the normal specifications,
expectations, and capabilities of virtually all Forth implementations.
     Again, I think I will show the solutions before explaining:

     Problem 1.
        V @ 84 c!
        H @ 85!

     Problem 2.
        84 c@ H!
        85 @ V!

     Now, if you are not a Forth user, that may all look rather cryptic
(looks like a secret code to me), but let's translate it into pseudo-
English. The first line of the first problem might be read like this:

     V  means the location (or variable) called "V"
     @  means fetch the contents of that location
     84 means use the number 84
     c! means store the character (byte) that we fetched first into the
        location that we fetched second

     or, in shorter form,
     "V is to be fetched as the data and 84 is to be used as the address
     of a byte-sized memory store."

     The second line, then, would read essentially the same except that
the "!" used (instead of "c!") implies a full word (double byte) store, as
does DPOKE in BASIC A +.
     The similarity and symmetry of the solutions of Problems 1 and 2
are striking. Let us "read" the first line of the second problem:

     84 means use the number 84 (in this case, as a location)
     c@ means fetch the byte (character) at that location
     V  means fetch the location (variable) called "V"
     !  means store the data fetched first into the location fetched
        second

     And, again, the only difference between this and the next line is
that "@" (instead of "c@") implies a double-byte fetch (again, as does
DPEEK of BASIC A +).
     Neither is there space here nor it is appropriate now to discuss the
foibles of Forth's reverse Polish notation and its stacking mechanism,
but even dyed-in-the-wool algorithmic language freaks (like me) can
appreciate its advantages in situations such as those demonstrated
here.

C
No, that does not mean "Section C." Believe it or not, "C" is the name
of a computer language. In fact, it is one of the more popular computer