Chapter 6 Writing and Updating Record Data

When records are written to a file for the first time, they are usually written sequentially. Following execution of an FWRITE intrinsic, the logical record pointer is positioned at the next sequential record in key sequence or at the end-of-file marker if the record is the last in sequence.

Updating and deleting records also rely on pointer positioning. The logical and physical record pointers are usually positioned by a read procedure, as discussed in Chapter 5 “Reading File Data”. Typically, a read procedure precedes an update or delete procedure to verify that the correct record has been found. Table 6-1 “Pointer and Advance Flag Settings for Writing” specifies the advance flag and pointer usage of each of the writing, updating, and deletion intrinsics.