Software as a Product

Software as a product is a product, software, which is made to be sold to users, and users pay for licence which allows them to use it, in contrast to SaaS, where users buy a subscription and where the software is centrally hosted.
One example of software as a product has historically been Microsoft Office, which has traditionally been distributed as a file package using CD-ROM or other physical media or is downloaded over a network. Office 365, on the other hand, is an example of SaaS, where a monthly subscription is required.

Development effort estimation

In the book The Mythical Man-Month Fred Brooks tells that when estimating project times, it should be remembered that programming products are three times as hard to write as simple independent in-house programs, because requirement to work on different situations, which increases testing efforts and as a documentation.