Top Down Approach



A top-down design is essentially breaking down a system to gain insight into its compositional sub-systems. In a top-down approach an overview of the system is first formulated, specifying but not detailing any first-level subsystems. Each subsystem is then refined in greater detail, sometimes in many additional subsystem levels, until the entire specification is reduced to base elements. In short the top down approach means decomposing of the solution procedure into subtasks. This approach produces a readable and modular code that can be easily understood and maintained.


top down approach


Steps for breaking a problem into sub-problems involve the following steps:

1. Start with a simple and short statement of the problem. This is top level in the design.

2. In the next level, describe the program as sequence, selection or repetition of main tasks. These tasks are called modules and these are complete in themselves. However these are described in greater details in next level. A module should have just one entry point and exit point.

3. This process is repeated step by step till all modules are refined. This step-wise refinement stops when there are sufficient details to convert that procedure into program.

4. Pseudo code or flowcharts are used to represent the procedure at intermediate steps.

5. Individual.

Keywords: top down programming approach.