Routines
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2D1B: THE 'NUMERIC' SUBROUTINE
Used by the routines at OUT_SP_2, ALPHANUM, DEC_TO_FP and STK_DIGIT.
This subroutine returns with the carry flag reset if the present value of the A register denotes a valid digit.
Input
A Character code
Output
F Carry flag reset if the character is a digit (0-9)
NUMERIC 2D1B CP "0" Test against +30, the code for '0'.
2D1D RET C Return if not a valid character code.
2D1E CP $3A Test against the upper limit.
2D20 CCF Complement the carry flag.
2D21 RET Finished.
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