During last summer vacation I met one of my cousin after long time. He is studying Computer Science Engineering in Trichy. I asked him the difference between Top-down approach and Bottom-up approach. He told that in Top-down approach computer reads or executes code from top line to bottom line, in bottom up approach computer reads or executes code from bottom line to top line.
First of all I would like to make crystal clear that Top-down approach and Bottom-up approach does not involve in program execution.These approaches involve in software development.
Top-down approach:
C programmer follows Top-down approach. On other words procedural programming follows this approach. Top-down approach also called as step-wise approach.
Top-down approach starts with high level system or design then it goes to low level system or design or development.
Top-down approach first focus on abstract of overall system or project. At last it focuses on detail design or development.
In this approach first programmer has to write code for main function. In main function they will call other sub function. At last they will write code for each sub function.
Top-down approach expects good planning and good understanding of the system or project.
Bottom-up approach:
C++, Java programmer follows Bottom-up approach. On other words object oriented programming follows this approach.
Bottom-up approach starts with low level system or design or development. Then it looks for high level system or design.
Bottom-up approach initially focuses on detail design or development. At last it concentrates on abstract of over all system or project.
In this approach first programmer has to write code for modules. Then they look for integration of these modules.
Bottom-up approach is more suitable for a project or system which is going to start from some existing modules.
Top-down approach and Bottom-up approach:
Now a days modern software design combines both Top-down approach and bottom-up approach.
So far I have completed three projects. In my first project I followed Top-down approach. In my second project I followed bottom-up approach. In my last and third project I followed both Top-down approach and Bottom-up approach.
Interested To Inform
Kannan
