BBS: Inland Empire Archive
Date: 05-18-92 (21:21) Number: 112
From: MATT HART Refer#: NONE
To: BLAINE CARMICHAEL Recvd: NO
Subj: Help! Conf: (2) Quik_Bas
BC> I have it set up now, I have to edit the Data Type and recompile. I
BC> would like to be able to have some sort of data file that would hold the
BC> new Data Type and Old Data Type and make the changes to the file. This
There are several ways to do this. It depends on how you know you need
a new data type. Is this a change made through the course
of the project (A "Woops! I need another field!") or a user
selected change (Joe, let's add a field in our customer
database program we bought from Blaine).
In the first case, you simply need to convert existing
a sequential file which keeps information on the field of a
file. I use a program written to document file record
types. It has the structure:
Idx TYPE (1 byte) LENGTH (integer) COMMENTS (20 bytes)
1 A ?? Alpha-numeric / string
2 I 2 Integer
3 L 4 Long integer
4 S 4 Single precision
5 D 8 Double precision
6 C 8 Currency
The Idx numbers are the key to the conversion. When
inserting a line, the program will automatically assign a
new and unique index to the Idx field.
With this program, I save these structures in a data file
that has a similiar name to the program data file I.E.
Employee file is "EMPL.???" and the information file is
"EMPL.FIL". Here's a sample of it:
1 A 10 ID
2 A 15 First name
3 A 1 Middle Initial
4 A 15 Last Name
5 A 9 Social Security Number
6 A 25 Address
7 A 15 City
8 A 2 State
9 A 10 Zip Code
10 C 8 Salary
11 S 4 Standard Rate
If I need to change this, and have already entered dozens
of employees as test data, then I copy this EMPL.FIL to
EMPLFIL.OLD and run my program, insert lines and such where
needed. Then run an auto conversion program:
ftconvrt emplfil.old empl.fil data\EMPL.*
or
ftconvrt {old data file} {new data file} {files to change}
Not only do you always have a record of your data structures (and it all
prints out with "Page x of y" in a nice laser form layout)
but conversion is quick, simple, automatic.
Here's a side note on fielding data for your programs : You
can field within a FOR/NEXT loop, reading the info from a
sequential file, needing nothing more than the length of
each field.
FILE.DAT
25 (Record length)
5 (number of fields)
10,5,5,4,1 (field lengths)
OPEN "I",1,"FILE.DAT"
INPUT #1,Reclen
OPEN "R",2,"FILE.RND",Reclen
INPUT #1,NumFields
REDIM Dat$(1 TO NumFields)
Dum = 0
FOR i = 1 TO NumFields
INPUT #1,FldLen
FIELD 2,Dum AS Dummy$, FldLen AS Dat$(i)
Dum = Dum + FldLen
NEXT
CLOSE 1
Now buffer 2 is fielded into Dat$() with the proper lengths.
Okay - next item. A resizable, field changeable, all-
purposeable file type. This is best accomplished with a
file header. The only catch here is that the header may
have some wasted space depending on the record size. The
program described at the top can create such a header
pretty easily.
Header info:
Integer - Record Size
Integer - Number of Fields
4 bytes to start with.
OPEN "R",1,"FILE.DAT",2
FIELD 1,2 AS Num$
GET 1,1 : RecSize = CVI(Num$)
GET 1,2 : NumFields = CVI(Num$)
REDIM Dat$(1 TO NumFields),DatType$(1 TO NumFields),DatLen(1 TO NumFields)
Field info:
Integer - Field Length
2 byte Ascii - Field Type Identifier (A,I,S,L,D,C)
Rec = 3
FOR i = 1 TO NumFields
GET 1,Rec : Rec = Rec + 1
DatLen(i) = CVI(Num$)
GET 1,Rec : Rec = Rec + 1
DatType$ = RTRIM$(Num$)
NEXT
CLOSE 1
You need to figure out where the actual records begin (after the header).
FirstDataByte = Rec * 2
IF FirstDataByte MOD RecSize = 0 THEN
FirstRec = FirstDataByte \ RecSize
ELSE
FirstRec = FirstDataByte \ RecSize + 1
ENDIF
Dum = 0
OPEN "R",1,"FILE.DAT",RecSize
FOR i = 1 TO NumFields
FIELD 1,Dum AS Dummy$,DatLen(i) AS Dat$(i)
Dum = Dum + DatLen(i)
NEXT
This type of record is great for dBase type applications,
because you can dynamically change the record size and
type, and do conversions on the fly.
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* Origin: Midnight Micro! V.32/REL (918)451-3306 (1:170/600)
