Page 134 - Standard Handbook Of Petroleum & Natural Gas Engineering

Computer Applications 119

CLOSE(1ist of specifiers)-Disconnects a file. The specifiers may be:
UNIT = file unit (device) number
IOSTAT as in OPEN
ERR as in OPEN
STATUS may be KEEP or DELETE

INQUIRE(1ist of specifiers)-Returns information about the attributes of a file.
Besides the UNIT = , IOSTAT and ERR specifiers, the following specifiers may
be included:

EXIST returns .TRUE. if file exists, else .FALSE.
OPENED returns .TRUE. if open, else .FALSE.
NUMBER returns number of connected device
NAMED returns .TRUE. or .FALSE.
NAME returns name of file
FORM returns FORMATTED or UNFORMATTED
RECL returns record length in direct access file
NEXT REC returns number of next record in direct access file
BLANK returns whether blanks or zeros specified

The following statements must include the UNIT = and may include the IOSTAT
and/or the ERR specifiers:
REWIND(1ist of specifiers) - Causes a sequential file to be rewound to
first record
BACKSPACE(1ist of specifiers) - Causes a sequential file to rewind one record
ENDFILE(1ist of specifiers) - Places an end-of-file mark on a sequential
file

A few examples of file-handling statements are:
OPEN(UN1T = 6,IOSTAT = FSTAT,FILE = ‘PRINTER’,STATUS = ‘NEW’
OPEN(4,FILE = ‘DATAl’,STATUS = ‘OLD’)
CLOSE(6)
BACKSPACE(4,ERR = 500)

Control statements affect the flow of instructions within a program unit. For
control between units, see subprogram statements later.) These may be general,
conditional, or iterative statements. General control statements are:

PAUSE n-Interrupts program run, resumption upon pressing “Enter”; n is
an optional character constant or integer of less than 5 digits, e.g.,
PAUSE ‘VALUE INVALID’
STOP n-Halts program run (n as above)
STOP 10050
GOTO i-Transfers control to statement labeled i, where i is an integer
constant or variable with value of label, e.g.,
GOTO 700