Many of the early sewing machines were powered by a treadle mechanism. The treadle was operated by pressing down on it with a foot, or both feet, to cause a rocking movement. This movement spins a large wheel on the treadle frame, connected by a thin leather belt to a smaller driving wheels on the sewing machine.
null. adj. 1. Having no legal force; invalid: render a contract null and void.2.ull. adj. 1. Having no legal force; invalid: render a contract null and void. 2.
Dynamically-typed languages with null include: 1  Perl scalar variables default to undef and can be set to undef. 2  PHP with NULL type and is_null() method, native nullable type in version 7.1. 3  Python has the None value. 4  Ruby with nil value and NilClass type. 5  JavaScript has a null value.