Accessing Files Programmer's Guide (32650-90885)

110 Chapter7
Record Selection and Data Transfer
Record Selection
Figure 7-1. Record Pointers
Following initialization, the record pointer may remain in position at the head of your file,
or it may be moved by the intrinsics used in record selection.
Record Selection
How are records selected for transfer? The file system intrinsics listed in Table 7-1. are
designed to move records to and from your file, but how do they choose the records they
want? The record pointer indicates the specific location where a file will be accessed;
records can be transferred to or from this location, or the pointer can be moved to another
place in the file that you wish to access.
There are five methods of record selection that you can use to access your file:
• sequential access, in which you transfer data to and from the place the record pointer
currently indicates
• random access, in which you move the record pointer before transferring data
• update access, in which you choose a record and write a new record over it