Prev: 02050 Up: Map Next: 02230
Used by the routine at SAVE_ETC.
This routine controls the LOADing of a BASIC program, and its variables, or an array.
HL Destination address (PROG, or the address of the array, or 0 for a new array)
IX Address of the header loaded from tape
LD_CONTRL 02056 LD E,(IX+11) Fetch the 'number of bytes' as given in the 'new header'.
02059 LD D,(IX+12)
02062 PUSH HL Save the 'destination pointer'.
02063 LD A,H Jump forward unless trying to LOAD a previously undeclared array.
02064 OR L
02065 JR NZ,LD_CONT_1
02067 INC DE Add three bytes to the length - for the name, the low length and the high length of a new variable.
02068 INC DE
02069 INC DE
02070 EX DE,HL
02071 JR LD_CONT_2 Jump forward.
Consider now if there is enough room in memory for the new data block.
LD_CONT_1 02073 LD L,(IX-6) Fetch the size of the existing 'program+variables or array'.
02076 LD H,(IX-5)
02079 EX DE,HL
02080 SCF Jump forward if no extra room will be required (taking into account the reclaiming of the presently used memory).
02081 SBC HL,DE
02083 JR C,LD_DATA
Make the actual test for room.
LD_CONT_2 02085 LD DE,5 Allow an overhead of five bytes.
02088 ADD HL,DE
02089 LD B,H Move the result to the BC register pair and make the test.
02090 LD C,L
Now deal with the LOADing of arrays.
LD_DATA 02094 POP HL Fetch the 'pointer' anew.
02095 LD A,(IX+0) Jump forward if LOADing a BASIC program.
02098 AND A
02099 JR Z,LD_PROG
02101 LD A,H Jump forward if LOADing a new array.
02102 OR L
02103 JR Z,LD_DATA_1
02105 DEC HL Fetch the 'length' of the existing array by collecting the length bytes from the variables area.
02106 LD B,(HL)
02107 DEC HL
02108 LD C,(HL)
02109 DEC HL Point to its old name.
02110 INC BC Add three bytes to the length - one for the name and two for the 'length'.
02111 INC BC
02112 INC BC
02113 LD (23647),IX Save the IX register pair temporarily (in X-PTR) whilst the old array is reclaimed.
02120 LD IX,(23647)
Space is now made available for the new array - at the end of the present variables area.
LD_DATA_1 02124 LD HL,(23641) Find the pointer to the end-marker of the variables area - the '128-byte' (E-LINE).
02127 DEC HL
02128 LD C,(IX+11) Fetch the 'length' of the new array.
02131 LD B,(IX+12)
02134 PUSH BC Save this 'length'.
02135 INC BC Add three bytes - one for the name and two for the 'length'.
02136 INC BC
02137 INC BC
02138 LD A,(IX-3) 'IX+0E' of the old header gives the name of the array.
02141 PUSH AF The name is saved whilst the appropriate amount of room is made available. In effect BC spaces before the 'new 128-byte'.
02145 INC HL
02146 POP AF
02147 LD (HL),A The name is entered.
02148 POP DE The 'length' is fetched and its two bytes are also entered.
02149 INC HL
02150 LD (HL),E
02151 INC HL
02152 LD (HL),D
02153 INC HL HL now points to the first location that is to be filled with data from the tape.
02154 PUSH HL This address is moved to the IX register pair; the carry flag set; 'data block' is signalled; and the block LOADed.
02155 POP IX
02157 SCF
02158 LD A,255
Now deal with the LOADing of a BASIC program and its variables.
LD_PROG 02163 EX DE,HL Save the 'destination pointer'.
02164 LD HL,(23641) Find the address of the end marker of the current variables area - the '128-byte' (E-LINE).
02167 DEC HL
02168 LD (23647),IX Save IX temporarily (in X-PTR).
02172 LD C,(IX+11) Fetch the 'length' of the new data block.
02175 LD B,(IX+12)
02178 PUSH BC Keep a copy of the 'length' whilst the present program and variables areas are reclaimed.
02182 POP BC
02183 PUSH HL Save the pointer to the program area and the length of the new data block.
02184 PUSH BC
02185 CALL MAKE_ROOM Make sufficient room available for the new program and its variables.
02188 LD IX,(23647) Restore the IX register pair from X-PTR.
02192 INC HL The system variable VARS has also to be set for the new program.
02193 LD C,(IX+15)
02196 LD B,(IX+16)
02199 ADD HL,BC
02200 LD (23627),HL
02203 LD H,(IX+14) If a line number was specified then it too has to be considered.
02206 LD A,H
02207 AND 192
02209 JR NZ,LD_PROG_1 Jump if 'no number'; otherwise set NEWPPC and NSPPC.
02211 LD L,(IX+13)
02214 LD (23618),HL
02217 LD (IY+10),0
The data block can now be LOADed.
LD_PROG_1 02221 POP DE Fetch the 'length'.
02222 POP IX Fetch the 'start'.
02224 SCF Signal 'LOAD'.
02225 LD A,255 Signal 'data block' only.
02227 JP LD_BLOCK Now LOAD it.
Prev: 02050 Up: Map Next: 02230