User`s guide

146

CipherLab BASIC Compiler

User's Guide

5.20.1 DAT Files

This one has a sequential file structure, which is much like the ordinary sequential file but is

modified to support FIFO structure. We call this type of file as DAT file. Because DAT files

are usually used to store transaction data, they are also referred to as Transaction files. The

length of each record in the transaction file is limited to 250 bytes. For portable terminals, a

BASIC program can have up to 6 transaction files.

DEL_TRANSACTION_DATA

Purpose

To remove a block of transaction data from the default transaction file.

Syntax

DEL_TRANSACTION_DATA(N%)

Remarks

This command will only have an effect on the first (default) transaction file.

"N%" is an integer variable, determining how many transaction records to be

deleted and how to delete.

If "N%" is a positive integer, the specified number of records will be deleted from

the top of the transaction file 1, i.e. the oldest records will be deleted.

If "N%" is a negative integer, the specified number of records will be deleted from

the bottom of the transaction file 1, i.e. the latest records will be deleted.

Example

...

PRINT "Discard the latest transaction? (Y/N)"

...

Loop:

KeyData$ = INKEY$

IF KeyData$ = "" THEN

GOTO Loop

ELSE IF KeyData$ = "Y" THEN

DEL_TRANSACTION_DATA(-1)

END IF

...