Help format - %n.mhe
By default, help information (associated with the "?" format modifier) is
displayed at the bottom of the window. When %he is used, the point at which %he
appears in a format string specifies the location of the help information. The
information could (for example) be placed inside a box.
In the form %he (without the integer modifiers), the area for the help string
will be sized to fit the largest help string so far encountered. If further
help strings are supplied after %he, their lengths should not exceed this size.
In most cases help boxes are best placed at the bottom of a window. However, if
necessary, an earlier help string could be padded with spaces in order to
increase its size.
%20he fixes the size of the area to 20 standard characters on one line, whilst
%20.3he has the same width but occupies 3 lines.
In the following example the help information is placed in a box below the %rd
str='No of children:'
hlp='How many children have you got?'