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175D: THE 'OPEN-2' SUBROUTINE
Used by the routine at OPEN.
The appropriate stream data bytes for the channel that is associated with the stream being opened are found.
Input
Output
OPEN_2 175D PUSH HL Save HL.
175E CALL STK_FETCH Fetch the parameters of the channel code.
1761 LD A,B Give an error if the expression supplied is a null expression, e.g. OPEN #5,"".
1762 OR C
1763 JR NZ,OPEN_3
This entry point is used by the routine at OPEN_P.
Report F - Invalid file name.
REPORT_F 1765 RST $08 Call the error handling routine.
1766 DEFB $0E
Continue if no error occurred.
OPEN_3 1767 PUSH BC The length of the expression is saved.
1768 LD A,(DE) Fetch the first character.
1769 AND $DF Convert lower case codes to upper case ones.
176B LD C,A Move code to the C register.
176C LD HL,$177A The base address of the OPEN stream look-up table.
176F CALL INDEXER Index into this table and locate the required offset.
1772 JR NC,REPORT_F Jump back if not found.
1774 LD C,(HL) Pass the offset to the BC register pair.
1775 LD B,$00
1777 ADD HL,BC Make HL point to the start of the appropriate subroutine.
1778 POP BC Fetch the length of the expression before jumping to the subroutine.
1779 JP (HL)
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