# DRAND, DRANDM

Portability Functions: Return double-precision random numbers in the range 0.0 to 1.0, not including the end points.

## Module

USE IFPORT

result = DRAND (iflag)

result = DRANDM (iflag)

iflag | (Input) INTEGER(4). Controls the way the random number is selected.

## Results

The result type is REAL(8). DRAND and DRANDM return random numbers in the range 0.0 to 1.0, not including the end points.

Value of iflag | Selection process
--- | ---
1 | The generator is restarted and the first random value is selected.
0 | The next random number in the sequence is selected.
Otherwise | The generator is reseeded using iflag, then restarted, and the first random value is selected.

There is no difference between DRAND and DRANDM. Both functions are included to insure portability of existing code that references one or both of them.

The intrinsic subroutines RANDOM_INIT, RANDOM_NUMBER, and RANDOM_SEED provide the same functionality and they are the recommended functions to use when writing programs to generate random numbers.

## Example

    USE IFPORT
    REAL(8) num
    INTEGER(4) f
    f=1
    CALL print_rand
    f=0
    CALL print_rand
    f=22
    CALL print_rand
    CONTAINS
      SUBROUTINE print_rand
        num = drand(f)
        print *, 'f= ',f,':',num
      END SUBROUTINE
    END

Parent topic: C to D

## See Also

RANDOM_INIT
RANDOM_NUMBER
RANDOM_SEED