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Routines |
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The address of this routine is found in the table of addresses. It is called indirectly via fp_calc_2.
This subroutine ('USR number' as distinct from 'USR string') handles the function USR X, where X is a number. The value of X is obtained in BC, a return address is stacked and the machine code is executed from location X.
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| usr_no | 13491 | CALL FIND_INT2 | Evaluate the 'last value', rounded to the nearest integer; test that it is in range and return it in BC. | |
| 13494 | LD HL,11563 | Make the return address be that of the subroutine STACK_BC. | ||
| 13497 | PUSH HL | |||
| 13498 | PUSH BC | Make an indirect jump to the required location. | ||
| 13499 | RET | |||
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Note: it is interesting that the IY register pair is re-initialised when the return to STACK_BC has been made, but the important HL' that holds the next literal pointer is not restored should it have been disturbed. For a successful return to BASIC, HL' must on exit from the machine code contain the address of the 'end-calc' instruction at 10072.
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