Now we will learn about procedure definitions, a much more powerful abstraction technique by which a compound operation can be given a name and then referred to as a unit.

• 现在我们来学习过程定义,这是一种威力更加强大的抽象技术,通过它可以为复合操作提供名字,而后就可以将这样的操作作为一个单元使用了。