| Routines

25F8: THE 'SCANNING RND' ROUTINE

The address of this routine is derived from an offset found in the scanning function table.
S_RND | 25F8 | CALL SYNTAX_Z | Unless syntax is being checked, jump to calculate a random number.
| 25FB | JR Z,S_RND_END
| 25FD | LD BC,($5C76) | Fetch the current value of SEED.
| 2601 | CALL STACK_BC | Put it on the calculator stack.
| 2604 | RST $28 | Now use the calculator.
| 2605 | DEFB $A1 | stk_one
| 2606 | DEFB $0F | addition: The 'last value' is now SEED+1.
| 2607 | DEFB $34 | stk_data: Put the number 75 on the calculator stack.
| 2608 | DEFB $37,$16
| 260A | DEFB $04 | multiply: 'last value' (SEED+1)*75.
| 260B | DEFB $34 | stk_data: Put the number 65537 on the calculator stack.
| 260C | DEFB $80,$41,$00,$00,$80
| 2611 | DEFB $32 | n_mod_m: Divide (SEED+1)*75 by 65537 to give a 'remainder' and an 'answer'.
| 2612 | DEFB $02 | delete: Discard the 'answer'.
| 2613 | DEFB $A1 | stk_one
| 2614 | DEFB $03 | subtract: The 'last value' is now 'remainder' - 1.
| 2615 | DEFB $31 | duplicate: Make a copy of the 'last value'.
| 2616 | DEFB $38 | end_calc: The calculation is finished.
| 2617 | CALL FP_TO_BC | Use the 'last value' to give the new value for SEED.
| 261A | LD ($5C76),BC
| 261E | LD A,(HL) | Fetch the exponent of 'last value'.
| 261F | AND A | Jump forward if the exponent is zero.
| 2620 | JR Z,S_RND_END
| 2622 | SUB $10 | Reduce the exponent, i.e. divide 'last value' by 65536 to give the required 'last value'.
| 2624 | LD (HL),A
S_RND_END | 2625 | JR S_PI_END | Jump past the S_PI routine.