SQUARE

 !Program name: SQUARE

!Find approximate square root

Implicit none

Real, allocatable :: x, a, b

allocate (x)

allocate (a)

allocate (b)

Write (*,*) 'Enter a number to find its approximate square root: '

Read *, x

!use the first routine with EXIT statement

a=1; b=x/a

do

  a=(a+b)/2.0

  b=x/a

  print *, 'New approximation of square root of', x, 'is: ', a

  if ( abs(a-b) < 1e-10 ) then

      exit

  end if

end do

Print *

Print *, 'Precise square root of', x, 'is: ', sqrt(x)

deallocate (a)

deallocate (b)

!Use the second routine with WHILE STATEMENT

a=1; b=x/a

do  while  ( abs(a-b) > 1e-10 )  !inverted logical expression

  a=(a+b)/2.0

  b=x/a

  print *, 'New approximation of square root of', x, 'is: ', a

end do

Print *

Print *, 'Precise square root of', x, 'is: ', sqrt(x)

end