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.
Introduced by the creator of the relational database model, E. F. Codd, SQL Null serves to fulfill the requirement that all true relational database management systems (RDBMS) support a representation of missing information and inapplicable information.