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Introduction
In the preceeding sections we have only considered I/O
(input output) to the user's terminal. Here we introduce
the general I/O to all possible devices (including the user's
terminal). READ inputs data from the device and WRITE
outputs data to it. The statements
have a format reference and an I/O list and
also normally have a logical unit number that uniquely identifies
the device.
The normal sequence for I/O is as follows. First the
OPEN statement is used to identify the device (and if necessary the file
name). The statement may contain details about the state of file
and the method of access. It also associates an arbitary logical
unit number to the device. Next come READs and WRITEs to carry
out the I/O and finally CLOSE to terminate the I/O. All these
statements are used in the program below which transfers 10 records
from a file INPUT.DAT to a file OUTPUT.DAT. Each record contains
3 real numbers in F10.4.
C Open the files
LUNIN=20
LUNOUT=21
OPEN(UNIT=LUNIN,FILE='INPUT.DAT',STATUS='OLD')
OPEN(UNIT=LUNOUT,FILE='OUTPUT.DAT',STATUS='NEW')
C Transfer the data
DO 100 IREC=1,10
READ(LUNIN,90000) X1,X2,X3
100 WRITE(LUNOUT,90000) X1,X2,X3
C Close the files
CLOSE(UNIT=LUNIN)
CLOSE(UNIT=LUNOUT)
STOP
90000 FORMAT(3F10.4)
END
n west (APC)
2000-03-08