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11405: THE 'ALPHA' SUBROUTINE
Used by the routines at DEF_FN, INPUT, S_FN_SBRN, LOOK_VARS and usr.
The routine at ALPHANUM continues here.
This subroutine returns with the carry flag set if the present value of the A register denotes a valid letter of the alphabet.
Input
Output
ALPHA 11405 CP "A" Test against 41 hex, the code for 'A'.
11407 CCF Complement the carry flag.
11408 RET NC Return if not a valid character code.
11409 CP 91 Test against 5B hex, 1 more than the code for 'Z'.
11411 RET C Return if an upper case letter.
11412 CP "a" Test against 61 hex, the code for 'a'.
11414 CCF Complement the carry flag.
11415 RET NC Return if not a valid character code.
11416 CP 123 Test against 7B hex, 1 more than the code for 'z'.
11418 RET Finished.
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