The ABS function returns the absolute value of a numeric argument.
Syntax
ABS (a)
a is an INTENT(IN) scalar or array of type REAL, INTEGER, or COMPLEX.
If a is INTEGER or REAL, the result is the same type and kind as a and has the value |a|.
If a is COMPLEX with value (x,y), the result is a REAL value with the same kind as a, and
is a representation of
real :: y=-4.5
complex :: z=(1.,-1.)
write(*,*) abs(y) ! writes 4.5000000
write(*,*) abs(z) ! writes 1.4142135