Many processes retrieve records in a sequence, to systematically perform a
function on each record. The primary key sequence is usually used for such
routines. The file opening routine (an HPFOPEN or FOPEN
intrinsic call) prepares for the most common record retrieval method by
positioning the pointers at the record containing the lowest value of the
primary key. A call to the FREAD intrinsic, after the file is opened,
reads the first record in the primary key sequence.
After reading the first record, the logical record pointer remains in the same
position. The next FREAD repositions the logical pointer as well as
the physical record pointer to the next sequential record in ascending key
sequence and reads the record. Although FREAD may position both
pointers, it uses the logical data pointer to locate the particular record. An
end-of-data condition occurs when the last logical record is passed. At this
point, the CCG condition code is set and returned to your process.
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