File organization refers to the way records are physically arranged on a storage device.
Intel Fortran supports two kinds of file organization:
Sequential
Relative
The default file organization is always ORGANIZATION= 'SEQUENTIAL' for an OPEN statement. The organization of a file is specified by means of the ORGANIZATION specifier in the OPEN statement.
You can store sequential files on magnetic tape or disk devices, and can use other peripheral devices, such as terminals, pipes, and line printers as sequential files.
You must store relative files on a disk device.
A sequentially organized file consists of records arranged in the sequence in which they are written to the file (the first record written is the first record in the file, the second record written is the second record in the file, and so on). As a result, records can be added only at the end of the file.
Sequential files are usually read sequentially, starting with the first record in the file. Sequential files with a fixed-length record type that are stored on disk can also be accessed by relative record number (direct access).
Within a relative file are numbered positions, called cells. These cells are of fixed equal length and are consecutively numbered from 1 to n, where 1 is the first cell, and n is the last available cell in the file. Each cell either contains a single record or is empty.
Records in a relative file are accessed according to cell number. A cell number is a record's relative record number (its location relative to the beginning of the file). By specifying relative record numbers, you can directly retrieve, add, or delete records regardless of their locations (direct access). (Detecting deleted records is only available if you specified the -vms option when the program was compiled.)
When creating a relative file, use the RECL value to determine the size of the fixed-length cells. Within the cells, you can store records of varying length, as long as their size does not exceed the cell size.