The SRS document produced at the end of requirement analysis and specification…

Concept: A software system can be described as a black box — a specification that documents only its externally visible behaviour (the inputs it accepts and the outputs/responses it produces) without disclosing anything about its internal implementation, algorithms, or code structure. Application: The SRS document is produced right at the end of requirement analysis and specification, before any design work begins. At this stage the document records what the system must do: its functional requirements, non-functional requirements, and expected input–output behaviour, exactly as an end user would observe it. It deliberately leaves out how those requirements will be implemented internally, so it fits the black-box view of the system.

• White-box specification would describe the system's internal implementation and logic in detail — the opposite of what an SRS captures, since an SRS intentionally omits internal working.

• A design plan documents how the system's components, modules, and data structures will be built — that is created during the design phase, which comes after requirement analysis, not at its end.

• Architectural design specifically records the high-level structure of subsystems and how they interact — again a design-phase artifact produced later, not the output of requirement analysis.

Result: Because the SRS document produced at the end of requirement analysis specifies only the externally observable behaviour of the system without revealing internal implementation, it is termed the black-box specification of the system.