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13574: THE 'LESS THAN ZERO' OPERATION (offset 54)
The address of this routine is found in the table of addresses. It is called via the calculator literal 54 by the routines at NEXT_LOOP, PRINT_FP, int, get_argt and atn.
This subroutine returns a 'last value' of one if the present 'last value' is less than zero and zero otherwise. It is also used by other subroutines to 'jump on minus'.
HL Address of the first byte of the number
less_0 13574 XOR A Clear the A register.
This entry point is used by the routine at greater_0 with A=255.
SIGN_TO_C 13575 INC HL Point to the sign byte.
13576 XOR (HL) The carry is reset for a positive number and set for a negative number; when entered from greater_0 the opposite sign goes to the carry.
13577 DEC HL
13578 RLCA
This routine continues into FP_0_1.
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