The waterfall development model was originally used in manufacturing and construction where changes are very expensive, and was adapted for early software development since there were no other formal methods. This hardware-oriented waterfall model structures development into sequential phases like requirements, design, implementation, testing, and maintenance.

1. The waterfall development model originates in the manufacturing and construction industries; highly structured physical environments in which after-the-fact changes are prohibitively costly, if not impossible. Since no formal software development methodologies existed at the time, this hardware-oriented model was simply adapted for software development.

3. tgyuuuuuuuuuuuuuuuu