What is the primary purpose of Software Requirements Specification (SRS)…

Concept: A Software Requirements Specification (SRS) is the formal document produced during requirements engineering. Its purpose is to comprehensively and unambiguously capture WHAT the system must do — the functional requirements (features, behaviours, inputs/outputs) — together with the quality attributes it must satisfy — the non-functional requirements (performance, security, reliability, usability). It serves as the agreed baseline between stakeholders, designers, and testers for the rest of the development lifecycle.

Application: Applying this to the item — an SRS document exists specifically to define the software's functional and non-functional requirements, so that is exactly what its primary purpose is.

• Listing the programming languages used is an implementation/technology-stack decision made during design, after requirements are already fixed — it is not what an SRS document itself records.

• Describing the user-interface design is design-phase work captured in UI/UX specifications or wireframes, not the defining content of a requirements-specification document.

• Defining the software's functional and non-functional requirements together is precisely what a requirements-specification document exists to record.

• Specifying the hardware components required belongs to a system/hardware specification or deployment plan, not to a software requirements-specification document.

Cross-check: Standard requirements-engineering references (e.g. the IEEE/ISO/IEC 29148 structure for an SRS) organize the document around a functional-requirements section and a non-functional-requirements section — confirming that defining both is the document's core purpose, distinct from the implementation, UI-design, and hardware-specification concerns raised by the other options.

Result: The primary purpose of an SRS document is to define the software's functional and non-functional requirements.