Two dimensional arrays or matrices of data occur naturally in many areas of engineering, science and business. Any kind of tabular data, such as results of an experiment or the performance of a company or stock can be considered a matrix.

In FORTRAN, we have to define the number of ROWS and the number of COLUMNS of a matrix in that order after the variable name in the declaration statements.

General form :

NAME_OF_MATRIX(ROWS,COLUMNS)

Examples :

INTEGER :: DAYS(12,31)

REAL :: YSALES(12,2)

CHARACTER (LEN=3) :: SEASON(4,3)

* Arrays are stored by columns.

PROGRAM MATRICES

IMPLICIT NONE

CHARACTER(LEN=3) :: MONTHS(3,4)

READ 33,MONTHS

33 FORMAT (12(' ',A3))

PRINT 33,MONTHS

L1: DO I=1,3

     L2: DO J=1,4

          PRINT 40,I,J,MONTHS(I,J)

40         FORMAT (' ROW ',I1,' COLUMN ',I1,' IS ',A3)

     END DO L2

END DO L1

STOP

END PROGRAM MATRICES

/DATA

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

/ENDRUN

OUTPUT :

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

ROW 1 COLUMN 1 IS JAN

ROW 1 COLUMN 2 IS APR

ROW 1 COLUMN 3 IS JUL

ROW 1 COLUMN 4 IS OCT

ROW 2 COLUMN 1 IS FEB

:

SEE EXAMPLES :

P71.F90 MATRIX INPUT/OUTPUT

P72.F90 MATRIX SUMMARY

P73.F90 MATRIX MULTIPLICATION PROGRAM

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