Commodore 1581 - Writing the Record

string-handling functions, and then all written out at once from that
variable.
Here is an example. If we are writing a 4-line mail label, consist
ing of 4 fields named "NAME," "STREET," "CITY & STATE," and "ZIP
CODE," and have a total record size of 87 characters, we can organize
it in either of two ways:
WITH FIXED LENGTH FIELDS
Field Name
NAME
STREET
CITY & STATE
ZIP CODE
Total length
Length
27 characters
27 characters
23 characters
10 characters
87 characters
WITH VARIABLE LENGTH FIELDS
Field Name
NAME
STREET
CITY & STATE
ZIP CODE
Potential length
Edited length
Length
31 characters
31 characters
26 characters
11 characters
99 characters
87 characters
With fixed length records, the field lengths add up to exactly the
record length. Since the total length is just within the Input buffer size
limitation, no carriage return characters are needed. With variable
length records, you can take advantage of the variability of actual
address lengths. While one name contains 27 letters, another may have
only 15, and the same variability exists in street and city lengths.
Although variable length records lose one character per field for
carriage returns, they can take advantage of the difference between
maximum field length and average field length. A program that uses
variable record lengths must calculate the total length of each record
as it is entered, to be sure the total of all fields doesn't exceed the
space available.
WRITING THE RECORD
Here is an example of program lines to enter variable length
fields for the above file design, build them into a single string, and
send them to record number RE in file number 3 (assumed to be a
relative file that uses channel number 3).
BASIC 7.0:
100 INPUT'ENTER RECORD NUMBER";RE
110:
120 DOPEN#3,"MYRELFILE",L88
130CR$ = CHR$(13)
140 INPUTNAME"; NA$
150 IF LEN(A$)>30 THEN 140
160 INPUT'STREET";SA$
170 IF LEN(SA$)>30 THEN 160
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