What is occurring when a programmer starts writing a program in C++ to convert units?

The process described, where a programmer begins writing a program in C++ to convert units, is categorized as implementation. This phase involves translating the program design and specifications into actual code. During implementation, the programmer creates the software functionality based on the earlier planning and design stages.

In this context, the programmer takes the requirements and designs the program logic into lines of code, effectively bringing the concept to life. The act of writing the program means that the coding stage is underway, which is the essence of implementation. This contrasts with earlier phases like analysis, where needs are identified, or design, where the architecture and flow of the program are established, both of which precede coding. Testing would come after implementation, focused on verifying that the code works as intended and meets the specified requirements.