Whether or not programmers take steps to make their code reliable and easy to change will show up on the balance sheets of businesses of all sizes.

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Practices that were known to produce more reliable software, and that make software easier to adapt and evolve, have been understood for decades.

software of good quality is:

reliable code, easy to change – adapt and evolve.

i.e., to become more agile.. is to improve quality of software.. is:

to produce more reliable code, make it easier to change, easier to adapt, easier to evolve