| Top-Down Method | Bottom-up Method |
| The principle of the top-down method dictates that a program should be divided into the main module and its related module. Each module should also be divided into sub-modules according to software engineering and programming style. The division continues until the module consists only of an elementary process that is intrinsically understood and cannot be further subdivided. | Bottom-up method is just the opposite of the top-down method. It refers to a style of programming in which an application is constructed with existing primitives of the programming language and then gradually more and more complicated features are added till applications are written. In other words, initiating the design with simple modules and then build them into more complex structures ending at the top is a bottom-up method. |
