diff --git a/src/stdlib_ascii.f90 b/src/stdlib_ascii.f90
index c1b159bc7..2bcfdfdc8 100644
--- a/src/stdlib_ascii.f90
+++ b/src/stdlib_ascii.f90
@@ -144,14 +144,17 @@ pure logical function is_graphical(c)
     pure logical function is_printable(c)
         character(len=1), intent(in) :: c !! The character to test.
         integer :: ic
-        ic = iachar(c)                    ! '~'
-        is_printable = c >= ' ' .and. ic <= int(z'7E')
+        ic = iachar(c)
+        !The character is printable if it's between ' ' and '~' in the ASCII table
+        is_printable = ic >= iachar(' ') .and. ic <= int(z'7E')
     end function
 
     !> Checks whether `c` is a lowercase ASCII letter (a .. z).
     pure logical function is_lower(c)
         character(len=1), intent(in) :: c !! The character to test.
-        is_lower = (c >= 'a') .and. (c <= 'z')
+        integer :: ic
+        ic = iachar(c)
+        is_lower = ic >= iachar('a') .and. ic <= iachar('z')
     end function
 
     !> Checks whether `c` is an uppercase ASCII letter (A .. Z).