It is absolutely essential, otherwise you will not have real idea of what you are dealing with. Project that have no real planning to them normally end early and badly.

Feature list, I diagram out how things will work on a dry erase board. I find the complicated algorithms I will have to do and start figuring them out so I have an idea what I am up against. I will also make a flowchart of what the basic interface will look like, if it is unclear what the interface will look like I will do a flowchart of what has to happen for each process to take place.

The coding is only one stage of development, programmers often neglect this. It is like saying that driving is the most important part so planning out how to get to your destination is not necessary. If you just leave and hope to find your way, chances are you are going to waste your time with a lot of unnecessary driving. Know exactly what you are going to do before you start coding the program.

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