List 4 advantages and disadvantages of bottom up approach.

Bottom-up Programming Approach

• In the Bottom-up programming approach, each small part of the program is constructed first in detail then all parts connect together to build a complete main program.
• The Bottom-up is based on the composition approach.
• Bottom-up programming is the total opposite of top-down programming.
• In this approach, the application is constructed starting with existing primitives of the programming language, and constructing gradually more and more complicated features, until all of the application has been written.

Advantages

1. This approach uses data encapsulation and data hiding while programming which minimizes the data redundancy.
2. The bottom-up approach has high interactivity between various modules.
3. Small parts of programs written in the bottom-up approach tend to be more general and thus more reusable, than parts of programs written top-down approach.
4. The bottom-up approach is more suitable when a system needs to be created from some existing components.
5. Using this approach it is very easy to make decisions about low or initial stage reusable components and how to integrate them to build a high or final stage system.
6. This approach is best suitable for testing the program because no need to use a stub.

Disadvantages

1. In the bottom-up approach, sometimes it is difficult to identify the overall functionality of the system at the initial stages.
2. The structure of functionality you establish first might have to be changed in a later roll-out phase.
3. In the bottom-up approach, all sub-parts are implemented even though some of the solutions of the sub-parts are not needed to solve, which requires additional calculations.
4. The program as an entity does not exist until the last main module is added.
5. This is not a natural method for people to assemble.