User`s guide

210 VEE User’s Guide
5 Storing and Retrieving Test Results Chapter
Using the To/From File Objects
The To File and From File objects read data to and from files
based on I/O transactions. They have the following
characteristics:
• A data file is opened on the first READ or WRITE
transaction. When the program ends, VEE closes any open
files automatically.
• VEE maintains one read pointer and one write pointer per
file regardless of how many objects are accessing the file. The
read pointer identifies the next data item to be read, and the
write pointer indicates where the next data item should be
written.
• The To/From File objects can append data to existing files or
overwrite them. If the Clear File at PreRun & Open setting is
checked in the open view of the To File object, then the write
pointer starts at the beginning of the file. If not, the pointer is
positioned at the end of the existing file. Each WRITE
transaction appends information to the file at the location of
the write pointer. If an EXECUTE CLEAR transaction is
performed, the write pointer moves to the beginning of the
file and erases its contents.
• A read pointer starts at the beginning of a file, and advances
through the data depending on the READ transactions. You
may perform an EXECUTE REWIND in the From File object
to move the pointer back to the beginning of the file without
affecting any data.
Understanding I/O Transactions
I/O transactions are used by VEE to communicate with
instruments, files, strings, the operating system, interfaces,
other programs, and printers. For example, look at the To File
object in Figure 128.
NOTE
The To File object is also described in “Lab 2-3: Using Data Files” on
page 85 of Chapter , “Agilent VEE Programming Techniques.”