I/O statements transfer all data as records. The amount of data that a record can contain depends on the following circumstances:
With formatted I/O (except for fixed-length records), the number of items in the I/O statement and its associated format specifier jointly determine the amount of data to be transferred.
With namelist and list-directed output, the items listed in the NAMELIST statement or I/O statement list (in conjunction with the NAMELIST or list-directed formatting rules) determine the amount of data to be transferred.
With unformatted I/O (except for fixed-length records), the I/O statement alone specifies the amount of data to be transferred.
When you specify fixed-length records (RECORDTYPE= 'FIXED'), all records are the same size. If the size of an I/O record being written is less than the record length (RECL), extra bytes are added (padding).
Typically, the data transferred by an I/O statement is read from or written to a single record. It is possible, however, for a single I/O statement to transfer data from or to more than one record, depending on the form of I/O used.
When using advancing I/O, if an input statement specifies fewer data fields (less data) than the record contains, the remaining fields are ignored.
If an input statement specifies more data fields than the record contains, one of the following occurs:
For formatted input using advancing I/O, if the file was opened with PAD='YES', additional fields are read as spaces. If the file is opened with PAD='NO', an error occurs (the input statement should not specify more data fields than the record contains).
For formatted input using nonadvancing I/O (ADVANCE='NO'), an end-of-record (EOR) condition is returned. If the file was opened with PAD='YES', additional fields are read as spaces.
For list-directed input, another record is read.
For NAMELIST input, another record is read.
For unformatted input, an error occurs.
If an output statement specifies fewer data fields than the record contains (less data than required to fill a record), the following occurs:
With fixed-length records (RECORDTYPE= ' FIXED ' ), all records are the same size. If the size of an I/O record being written is less than the record length (RECL), extra bytes are added (padding) in the form of spaces (for a formatted record) or zeros (for an unformatted record).
With other record types, the fields present are written and those omitted are not written (might result in a short record).
If the output statement specifies more data than the record can contain, an error occurs, as follows:
With formatted or unformatted output using fixed-length records, if the items in the output statement and its associated format specifier result in a number of bytes that exceeds the maximum record length (RECL), an error occurs.
With formatted or unformatted output not using fixed-length records, if the items in the output statement and its associated format specifier result in a number of bytes that exceeds the maximum record length (RECL), the Intel Fortran RTL attempts to increase the RECL value and write the longer record. To obtain the RECL value, use an INQUIRE statement.
For list-directed output and namelist output, if the data specified exceeds the maximum record length (RECL), another record is written.