Converting a string to a number using decimal prefixes.
(Spice-like format used in electrical circuit simulation programs).

Accepted decimal prefixes formats in this program :

Symbol	Prefix	Exponential equivalent
'f'	femto	1e-15
'p'	pico	1e-12
'n'	nano	1e-9
'u'	micro	1e-6
'm'	milli	1e-3
'c'	centi	1e-2
'h'	hecto	1e+2
'k'	kilo	1e+3
'meg'	mega	1e+6
'g'	giga	1e+9
't'	tera	1e+12
'pet'	peta	1e+15

Some features:

• instead of a decimal point, you can use a prefix: 1.3k = 1k3
• can put exponential format at the end
• spaces inside are ignored
• prefixes are automatically converted to uppercase during conversion

Example:

program main

implicit none
integer,parameter :: siz=6
type tmp
    character(:), allocatable :: words
endtype tmp

type (tmp) :: w(siz)          ! input array
real(8)    :: nums(siz)       ! output array

real(8)    :: numeric         ! function name
integer i

! Representation of the number 1230 in different formats  
    ! most often used:
    w(1)%words = ' 1.23k'  
    w(2)%words = ' 1,23k'
    w(3)%words = '1k23'
    
    ! this is for demonstration:
    w(4)%words = '1 m23e6'    
    w(5)%words = '1meg23e-3'  
    w(6)%words = '1.23e3'

    print '( a , *( a12) )', 'input words:  ', (w(i)%words, i=1,siz)

    do i=1,siz  
        nums(i) = numeric(w(i)%words)
    enddo
    
    print '( a, *(f11.1,1x) )', 'output numbers:', nums

end program main

Result:

input words:         1.23k       1,23k        1k23     1 m23e6   1meg23e-3      1.23e3
output numbers:     1230.0      1230.0      1230.0      1230.0      1230.0      1230.0

 For testing on used gfortran version 13.1 for Windows. The directory contains a Makefile for building using the make command.