Routines |
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Used by the routine at MAIN_EXEC.
This subroutine allows for a new BASIC line to be added to the existing BASIC program in the program area. If a line has both an old and a new version then the old one is 'reclaimed'. A new line that consists of only a line number does not go into the program area.
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MAIN_ADD | 155D | LD ($5C49),BC | Make the new line number the 'current line' (E-PPC). | |||||
1561 | LD HL,($5C5D) | Fetch CH-ADD and save the address in DE. | ||||||
1564 | EX DE,HL | |||||||
1565 | LD HL,$1555 | Push the address of REPORT_G on to the machine stack. ERR-SP will now point to REPORT_G. | ||||||
1568 | PUSH HL | |||||||
1569 | LD HL,($5C61) | Fetch WORKSP. | ||||||
156C | SCF | Find the length of the line from after the line number to the 'carriage return' character inclusively. | ||||||
156D | SBC HL,DE | |||||||
156F | PUSH HL | Save the length. | ||||||
1570 | LD H,B | Move the line number to the HL register pair. | ||||||
1571 | LD L,C | |||||||
1572 | CALL LINE_ADDR | Is there an existing line with this number? | ||||||
1575 | JR NZ,MAIN_ADD1 | Jump if there was not. | ||||||
1577 | CALL NEXT_ONE | Find the length of the 'old' line and reclaim it. | ||||||
157A | CALL RECLAIM_2 | |||||||
MAIN_ADD1 | 157D | POP BC | Fetch the length of the 'new' line and jump forward if it is only a 'line number and a carriage return'. | |||||
157E | LD A,C | |||||||
157F | DEC A | |||||||
1580 | OR B | |||||||
1581 | JR Z,MAIN_ADD2 | |||||||
1583 | PUSH BC | Save the length. | ||||||
1584 | INC BC | Four extra locations will be needed, i.e. two for the number and two for the length. | ||||||
1585 | INC BC | |||||||
1586 | INC BC | |||||||
1587 | INC BC | |||||||
1588 | DEC HL | Make HL point to the location before the 'destination'. | ||||||
1589 | LD DE,($5C53) | Save the current value of PROG to avoid corruption when adding a first line. | ||||||
158D | PUSH DE | |||||||
158E | CALL MAKE_ROOM | Space for the new line is created. | ||||||
1591 | POP HL | The old value of PROG is fetched and restored. | ||||||
1592 | LD ($5C53),HL | |||||||
1595 | POP BC | A copy of the line length (without parameters) is taken. | ||||||
1596 | PUSH BC | |||||||
1597 | INC DE | Make DE point to the end location of the new area and HL to the 'carriage return' character of the new line in the editing area (WORKSP-2). | ||||||
1598 | LD HL,($5C61) | |||||||
159B | DEC HL | |||||||
159C | DEC HL | |||||||
159D | LDDR | Now copy over the line. | ||||||
159F | LD HL,($5C49) | Fetch the line's number (E_PPC). | ||||||
15A2 | EX DE,HL | Destination into HL and number into DE. | ||||||
15A3 | POP BC | Fetch the new line's length. | ||||||
15A4 | LD (HL),B | The high length byte. | ||||||
15A5 | DEC HL | |||||||
15A6 | LD (HL),C | The low length byte. | ||||||
15A7 | DEC HL | |||||||
15A8 | LD (HL),E | The low line number byte. | ||||||
15A9 | DEC HL | |||||||
15AA | LD (HL),D | The high line number byte. | ||||||
MAIN_ADD2 | 15AB | POP AF | Drop the address of REPORT_G. | |||||
15AC | JP MAIN_EXEC | Jump back and this time do produce an automatic listing. |
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