Commodore 1581 - Reading a Relative Record

170 IF LEN>27 THEN 160
175 SA$ = SA$ + LEFT$(BL$,27 - LN)
180 INPUT'CITY & STATE"; CS$
185LN=LEN(CS$)
190IFLN>23THEN180
195 CS$ = CS$ + LEFT$(BL$,23 - LN)
200 INPtTTZIP CODE";ZP$
205LN=LEN(ZP$)
210IFLN>10THEN200
215 ZP$ = ZP$+LEFT$(BL$,10 - LN)
220 DA$ = NA$ + SA$ + CS$ + ZP$
260RH = INT(RE/256)
270RL=RE-256*RH
280 PRINT#15,"P" + CHR$(96 + 3) + CHR$(RL) + CHR$(RH) + CHR$(1)
290 GOSUB1000:IF EN = 50THENPRINT#3)CHR$(255):GOSUB1000:GOTO280
300 GOSUB1000
310 PRINT#3,DA$
320 GOSUB1000
330 PRINT#15,"P" + CHR$(96 + 3) + CHR$(RL) + CHR$(RH) + CHR$(1)
340 GOSUB1000
350 GOSUB1000:aOSE3:aOSE15:END
1000 INPUT#15,EN,EM$,ET,E
1002 IF EN<20 THEN RETURN
1010PRINT"ERROR;"EM$:aOSE3:aOSE15:END
If field contents vary in length, variable field lengths are often
preferable. On the other hand, if the field lengths are stable, fixed field
lengths are preferable. Fixed length fields are also required if you
want to use die optional offset parameter of the RECORD# command
to point at a particular byte within a record. However, when any part of
a record is written, DOS overwrites any remaining spaces in the
record. Thus, if you must use the offset option, never update any field
in a record other than the last one unless all succeeding fields will also
be updated from memory later.
The above programs are careful to match record lengths exactly
to the space available. Programs that don't do so will discover that
DOS pads short records out to full size with fill characters, and
truncates overlong records to fill only their allotted space. When a
record is truncated, DOS will indicate error 51, "RECORD OVER
FLOW," but short records will be accepted without a DOS error
message.
READING A RELATIVE RECORD
Once a relative record has been written properly to diskette,
reading it back into computer memory is fairly simple, but the proce
dure again varies, depending on whether it uses fixed or variable
length fields. Here are the program lines needed to read back the
64