Merits of bottom-up technique

The details of the sub-problem solutions are available in advance in the form of bottom level modules.
The individual sub-problem solutions are designed with great details.
The main solution can be planned later depending on the available sub-task solutions.
The main solution is used to link all the sub-problem solutions.
The sub-solutions obtained are simple
A complex main module is designed later using these simpler solutions.
This technique is more general and code are reusable.
This technique simplifies maintenance and the new features can be added easily.
This decision of the final solution can be delayed to make it more effective for implementation.
Testing in this case is simple and test cases can be designed very easily.