What is Necessary to Develop Software?

I will work from these definitions.

Software is a general term for the various kinds of programs used to operate computers and related devices.

A Program is a specific set of ordered operations for a computer to perform.

A Computer is a device that accepts information and operation instructions.

So, to rephrase the initial question, What is necessary to develop specific sets of ordered instructions for a computer to perform?

You will need:

- A computer
- A specification of the instructions the computer accepts
- Something to generate sequences of instructions

Something to generate sequences of instructions! Another computer could do this. A person could do this if the person has knowledge of the computer's instruction set.

A Programmer is a person that specifies a sequence of instructions for a computer.

I will not go into the roles of low level languages, high level languages, compilers, interpreters, and other methods of specifying computer instructions.

So, that is all that is necessary to develop computer programs.

What? You feel that there is more necessary? I don't think so.

Oh, you want to develop a specific program to solve a specific problem. Well then, it is necessary for you to describe the problem in terms such that the programmer can order the correct sequence of instructions for the computer to solve the problem.

Does the specification of the problem have to be done in a certain format? No. The only thing necessary is that you communicate to the programmer accurately the problem to be solved.

So, if you want a specific problem solved then you must define the requirements.

Now we are up to:
- A computer
- A specification of the instructions the computer accepts
- Something to generate sequences of instructions
- Specification of the problem requirements

Wait, does the problem specification include a description or specification of the solution? No, it does not. The expected results of a software program may be termed the solution set. For instance if the specification for the program says, "Enter two numbers and compute the multiplication of those two number and display them." If you enter the numbers 6 and 2 and the results where "To be or not to be? That is the question." clearly that result is not in the expected set of solutions for multiplication.

The specification of the solution set or correct set of results for a program are necessary if you only accept specific results.

Now we are up to:
- A computer
- A specification of the instructions the computer accepts
- Something to generate sequences of instructions
- Specification of the problem requirements
- Specification of acceptable results

Some might say the last to specifications go together into one specification. It doesn't matter to me. The point is, if you want specific problems to be solved and receive results in a specific set of possible results then it is necessary for those to be specified and communicated to the programmer.

So, that's all you need.

But you are thinking there is so much more to software development. There are books and books on how to write good solid code. There are books and books on how to organize teams. There are books and books on how to layout the User Interface.

Ultimately it all depends on what you want and what you value and the things you are willing to do to get the things you want.

Here are some related questions to the topic:
- What is necessary to develop software quickly?
- What is necessary to develop software with few defects?
- What is necessary to develop software that runs on many different computers?
- What is necessary to develop software inexpensively?
- What is necessary to stop developers from quitting?
- What is necessary to protect intellectual property?
- What is necessary to attract talented programmers?
- What is necessary to get incremental results from the development effort?
- What is necessary to build software for life critical systems?
- What is necessary to make code that is reusable?
- What is necessary to make code backwards compatible?
- What is necessary to develop software for moving/shifting requirements?

The list goes on and on and on.

Geoff