Page 132 - Standard Handbook Of Petroleum & Natural Gas Engineering

Computer Applications 117

Table 1-25
Precedence of FORTRAN Operators
Class Level Symbol or Mnemonic
EXPONENTIAL First tt
Second - (negation) and + (identity)
ARITHMETIC Third *, 1
Fourth +, -
RE L AT I 0 N A L Fifth .GT.,.GE.,.LT.,.LE.,.EQ.,.NE
Sixth .NOT.
Seventh .AND.
LOGICAL
Eighth .OR.
Ninth .EQV. ,.NEQV

where device# refers to either a device such as a screen or printer or to a disk
file. Usually the default input device (referenced by an asterisk rather than a
device#) is the keyboard and the default output device (also referenced by an
asterisk) is the screen. PRINT connects only to the printer. Other devices and
files may be assigned device numbers through file handling statements (see
later). A statement requesting list-directed input from the default device (the
keyboard) might be, for example,
READ( ",")TEMP,PRSSR,LENGTH

Formatted 1/0 statements require edit specifiers (see Table 1-26 for list) for
each variable to be handled and may also include strings of characters enclosed
in single quote marks. The format may be given in a separate format statement
(referenced by a line number and labeled) or, in many systems, may be enclosed
in quotes and parentheses in the 1/0 statement itself. The general form for
formatted 1/0 statements is
READ(device#,label)varl,var2, . . .
WRITE(device#,label)varl,var2, . . .
PRINT label varl,varZ, . . .
label FORMAT(1ist of specifications)
For example,

READ( *, lOO)X( l),Y,I
100 FORMAT( lX,2F12.4,15)
WRITE(6,l lO)(TEMP(I),I = 1,5)
110 FORMAT( lX,5(F7.3,2X))
WRITE( *,'( "TEMP AT SURFACE IS ",FS.S)')TSURF
File handling statements allow the manipulation of sequential and random
access files. (Since there is considerable variation from one system to the next,
the following information is given in general terms only.) Devices are treated