| Routines

19FB: THE 'E-LINE-NO' SUBROUTINE

Used by the routines at MAIN_EXEC and LINE_SCAN. This subroutine is used to read the line number of the line in the editing area. If there is no line number, i.e. a direct BASIC line, then the line number is considered to be zero.
Output
BC | Number of the line in the editing area (or +0000 if none)
E_LINE_NO | 19FB | LD HL,($5C59) | Pick up the pointer to the edit-line (E-LINE).
| 19FE | DEC HL | Set CH-ADD to point to the location before any number.
| 19FF | LD ($5C5D),HL
| 1A02 | RST $20 | Pass the first code to the A register.
| 1A03 | LD HL,$5C92 | However before considering the code make the calculator's memory area a temporary calculator stack area (by setting STKEND equal to MEMBOT).
| 1A06 | LD ($5C65),HL
| 1A09 | CALL INT_TO_FP | Now read the digits of the line number. Return zero if no number exists.
| 1A0C | CALL FP_TO_BC | Compress the line number into the BC register pair.
| 1A0F | JR C,E_L_1 | Jump forward if the number exceeds 65,536.
| 1A11 | LD HL,$D8F0 | Otherwise test it against 10,000.
| 1A14 | ADD HL,BC
E_L_1 | 1A15 | JP C,REPORT_C | Give report C if over 9,999.
| 1A18 | JP SET_STK | Return via SET_STK that restores the calculator stack to its rightful place.