Routines |
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Used by the routines at SAVE_ETC, SA_CONTRL, PO_SCR, CLS, CL_ALL, ED_EDIT, ED_UP, MAIN_EXEC, LIST, LPRINT, STR_ALTER, INPUT, str and read_in.
This subroutine is called with the A register holding a valid stream number - normally 253 to 3. Then depending on the stream data a particular channel will be made the current channel.
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CHAN_OPEN | 05633 | ADD A,A | The value in the A register is doubled and then increased by 22. | |||||
05634 | ADD A,22 | |||||||
05636 | LD L,A | The result is moved to L. | ||||||
05637 | LD H,92 | The address 23574 is the base address for stream 0. | ||||||
05639 | LD E,(HL) | Fetch the first two bytes of the required stream's data. | ||||||
05640 | INC HL | |||||||
05641 | LD D,(HL) | |||||||
05642 | LD A,D | Give an error if both bytes are zero; otherwise jump forward. | ||||||
05643 | OR E | |||||||
05644 | JR NZ,CHAN_OP_1 | |||||||
This entry point is used by the routine at STR_ALTER.
Report O - Invalid stream.
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REPORT_O | 05646 | RST 8 | Call the error handling routine. | |||||
05647 | DEFB 23 | |||||||
Using the stream data now find the base address of the channel information associated with that stream.
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CHAN_OP_1 | 05648 | DEC DE | Reduce the stream data. | |||||
05649 | LD HL,(23631) | The base address of the whole channel information area (CHANS). | ||||||
05652 | ADD HL,DE | Form the required address in this area. | ||||||
This routine continues into CHAN_FLAG.
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