| Register(s) | Usage |
|---|---|
| 0 |
Total # of permutations printed. (Incremented after printing a string
permutation.) R0 must be set to 0 before running the program.
|
| 6 |
Index in A of second character to be swapped? This register must be
initialized to N-1, one less that the length of the string,
before running the program. The full length of the string, N,
is stored in R19.
|
| 7 |
Stack pointer (SP). *R7 points to the memory register containing the
current call "frame". Pushing a call frame on the stack increments
R7 and popping a frame decrements R7. This register must be set to
8, thus pointing to the initial top of the stack, before running the
program.
|
| 08 - 18 |
The call stack, beginning with register 8 and growing upwards
(possibly to register 18). One call frame is stored per memory
register and is encoded as a number, "nnnnnnnnnn.ik", where the
ten integer digits (1-9 and 0) are the current configuration of
the permutation indices and the two fractional digits are the
values of local variables i and k, respectively. The very first
call frame, in register 8, is a setup parameter which must be set
prior to running the program; you only need to specify the indices
for the initial permutation string, "nnnnnnnnnn" (or fewer digits
for a shorter string).
|
| 19 |
The length, 1≤N≤10, of the string being permuted.
This is a setup parameter which must be set prior to running the
program.
|
| 20 - 29 |
Print codes, one letter per memory register. Registers 20-29 contain
the two-digit character codes for the characters corresponding to
indices 0, 1, 2, ..., 9 in the permutation string. For strings less
than 10 characters in length, index 0 and memory register 20 are
reserved for implicit leading blanks used to expand a permuted string
to 10 characters for printing; in this case, R20 must be set to 0.
The PC-100 alphanumeric character codes (decimal numbers, not octal!)
from Guillaume Tello's
Texas Instruments TI 58C/TI 59 page:
|