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Дата изменения: Sat Mar 23 14:10:50 1996 Дата индексирования: Mon Oct 1 20:56:00 2012 Кодировка: Поисковые слова: http astrokuban.info astrokuban |
PROGRAM - main program FUNCTION - function, FUNCTION can be preceded by some of the specifications of the variables below, except IMPLICIT SUBROUTINE - subroutine ??ENTRY - extra entry in subprograms ? BLOCK DATA - common data, usually given initial values
IMPLICIT - default IMPLICIT REAL(A-H, O-Z), INTEGER(I-N) IMPLICIT NONE - not standard, but very useful, it is available in Fortran 90. Gives the "Pascal convention" that all variables have to be specified. For Sun and DEC the same effect can be obtained with the switch -u in the compilation command INTEGER REAL DOUBLE PRECISION COMPLEX LOGICAL CHARACTER CHARACTER*4
DIMENSION - can also be given directly in the type specification, as well as in a COMMON ? COMMON - common storage area for variables that are in several program units ??EQUIVALENCE - common storage area for several variables in the same program unit PARAMETER - makes a variable into a constant with a certain value EXTERNAL - tells the system that the identifier is an external function or an external subroutine INTRINSIC - tells the system that the identifier is an intrinsic function (or a subroutine, only in Fortran 90) SAVE - saves the values between exit or return from one subroutine into the new call of the same subroutine or function DATA - puts initial values into variables
GOTO snr1 - ordinary GOTO statement (jumps to the statement with number snr1) ? GOTO (snr1, snr2, snr3), integer_expression - conditional GOTO statement. If the integer expression is 1, 2 or 3, execution jumps to statement number snr1, snr2 or snr3 (an arbitrary number of statement numbers snr are permitted). ??GOTO statement_number_variable, (snr1, snr2, snr3) - an assigned GOTO statement, jumps to the statement number that equals the statement number variable (an arbitrary number of statement numbers snr are permitted). ??GOTO statement_number_variable - this is an assigned ordinary GOTO statement, it is a combination of the first one, GOTO snr1, and previous one, GOTO statement_number_variable without a list of permitted alternatives. ??ASSIGN statement_number TO statement_number_variable - statement number variables can not be assigned with an ordinary assignment of the type (integer variable = integer expression), it has to be done with the ASSIGN statement. The statement number variable can then be used for an assigned GOTO statement and in the ordinary GOTO statement and also in connection with FORMAT. ? IF (numerical_expression) snr1, snr2, snr3 - arithmetical IF-statement, jumps to statement number snr1 if the expression is negative, snr2 if the expression is zero, snr3 if the expression is positive
IF(logical_expression) statement - conditional statement: if the logical expression is true, the statement is performed, in the other case execution jumps directly to the next statement. The statement here is permitted to be an ordinary assignment statement or an ordinary jump statement (GOTO statement) or a call of a subroutine. IF(logical_expression) THEN ! Complete alternative statement. ...statements... ! Variants without the ELSE-part as well ELSE ! as with nested ELSE, or with ...statements... ! ELSE replaced by ENDIF ! ELSE IF (log_expr) THEN ! also exist. CONTINUE - continuation, does nothing. It is recommended for clean conclusion of a DO-loop. STOP - concluding statement, stops execution. END - concluding statement, stops compilation of the program unit and also execution if it is in the main program. If END is found during execution of a subprogram, an automatic return to the calling program unit is executed (replaces the explicit RETURN statement). ? PAUSE - pause statement, stops execution temporarily (implementation dependent). DO statement_number variable = var1, var2, var3 - DO-loop. Floating-point numbers are permitted as variables in the DO-loop, but they are not recommended. It is preferable to use integers.
OPEN - open a file before the program can use it. CLOSE - close a file. A file that has not been closed can usually not be read. READ - input WRITE - output PRINT - previously output to line printer, now a synonym to WRITE. It works on a standard unit. INQUIRE - inquires about file status. REWIND - rewinds a file to the beginning. BACKSPACE - rewinds a file one record. ENDFILE - marks end of file. FORMAT - Fortran speciality (see below).
CALL sbrtn - call a subroutine sbrtn. fnctn - a function is called by giving the function name fnctn. RETURN - return from the subprogram (subroutine or function).
Example Comments ------------------------------------------------------------------- Integer I I5 5 positions reserved ------------------------------------------------------------------- Floating-point F F8.3 8 positions, out of which 3 are number used for the fractional part E E14.6 14 positions of which 6 are used for the decimals 4 - for the exponent 1 - for the sign 1 - for the starting zero 1 - for the decimal point 1 - for a blank character D D20.12 as E, but for double precision G G14.6 as F, if the number can be given within the field, else as E ------------------------------------------------------------------- Complex numbers as a pair of floating-point variables ------------------------------------------------------------------- Logical L L1 Character A A7 7 characters are available in A7 string ' ' 'Example' Conventional character constant nH 7HExample Hollerith constant (obsolete) Positioning Tn n positions from the left TLn n positions towards left TRn n positions towards right nX n positions towards right No new line $ this is used if you wish to do input in direct connection with an output, to stay on the same line. Not standard! Not Fortran 90! Discontinue : if the list does not contain any more elements the format is also finished here New record / normally a new line ------------------------------------------------------------------- Binary B not Fortran 77 but Fortran 90 Octal O not Fortran 77 but Fortran 90 Hexadecimal Z not Fortran 77 but Fortran 90 ------------------------------------------------------------------- Output SP + is written SS + is not written S standard (normal SS) In all alternatives a minus - is written for negative values ------------------------------------------------------------------- Input BZ blanks are interpreted as zeroes BN blanks are not regarded as anything (blanks are skipped) BN is standard using the ULTRIX, when punched cards were used, BZ was the standard. Compare with BLANK = "ZERO" and Blank = "NULL" in the OPEN-statement. ------------------------------------------------------------------- Scaling factor kP: Input: with an exponent, no action. Without exponent, the number is multiplied by 10**(-k) before assignment, which means a change of the value. Output: with exponent, the mantissa is multiplied by 10**k and the exponent is reduced with k, which means no change of the value. Without exponent, the number is multiplied by 10**k before the output, which means a change of value.NB! S, SP, SS, BN, BZ and kP are valid until the end of the FORMAT or until a new one of the same kind appears. To scale with kP is good with E-format on output, because then you avoid that the first digit is zero, and you get more information into less space on the paper. To scale with kP is catastrophic using F-format, but it was of great interest when punched cards were still in use.
A very good and complete description of input and output in Fortran, including the use of the FORMAT-letters, is given in the book by Adams et al (1992).
fpr < output_file | lpr -Pprinterwhere output_file is the name of the file to be printed with control characters and printer is the name of the printer to be used.
Further information on the ASA Control Characters are now available.