Reverse engineering is the process which deals with:

Concept

Reverse engineering is the process of analysing an existing software system to identify its components and their interrelationships, and to represent the system in another form or at a higher level of abstraction — the reverse of forward engineering, which moves from requirements down to code. Standard software-engineering taxonomy places two sub-activities under reverse engineering: redocumentation (producing a semantically equivalent representation of the system without changing it) and design recovery (reconstructing a valid, design-level abstraction of the system by combining source-code analysis with domain knowledge, personal experience, and any surviving documentation).

Application

Matching the four options against this taxonomy: only "design recovery" is a named sub-activity of reverse engineering. The remaining two component activities named in the option set belong to other software-engineering disciplines rather than to reverse engineering, and "All of the above" would require every one of the three to be a reverse-engineering activity:

• Size measurement (e.g. counting lines of code or function points) is a software-metrics activity used for estimation and productivity tracking, not a step of reverse engineering.

• Cost measurement (e.g. effort/cost estimation using a model such as COCOMO) is a project-planning activity performed before or during development, not an activity of analysing an existing system.

• "All of the above" fails because it bundles size measurement and cost measurement in with design recovery, and the first two are not reverse-engineering activities.

Cross-check

An independent check: reverse engineering is invoked precisely when a team must understand a legacy system whose documentation is missing or stale before they can safely modify it. The objective in that scenario is always to recover a design-level understanding — module boundaries, data structures, control flow — never to measure the system's size or the project's cost. That confirms design recovery as the process reverse engineering deals with.