$15-$ Heterogeneity means Systems are distributed and include a mix of hardware and software.

$17-$System engineering is part of Software engineering.

$18-$Evolution $-$ changing the software in response to changing demands $.$

$19-$Upper$-$CASE Tools to support later activities such as programming, debugging and testing.

$20-$A software process is A set of activities whose goal is the development or evolution of software.

$21-$A software process model is an abstract representation of a process.

$22-$The waterfall model Specification and development are interleaved.

$23-$ Formal systems development A logical system model is formally transformed to an implementation.

$24-$ Throw$-$away prototyping particularly unsuitable where: detailed requirements not possible.

$25-$ Risk assessment and reduction risks are assessed and activities put in place to reduce the key risks.