Sustained engineering takes over support of a Windows version on the date the code is "golden," or released to manufacturing. On that date, the source code is effectively split into three parts: the gold code goes to manufacturing and is archived, sustained engineering begins on the released version (Version n in the chart), and development begins on the next version (Version n+1). Windows Sustained Engineering (WSE) is already supporting the previous version (Version n-1).

When a customer reports a problem via Product Support Services or a vulnerability is reported through the Security Response Center, WSE helps triage the problem and then develops and tests the appropriate hotfix, security patch, or update for release via Windows Update and inclusion in the next service pack for that version.

WSE must also ensure that any change to the code to fix the problem or vulnerability is incorporated in the next version and, if appropriate, in the next service pack for the previous version.

Back to associated article: Windows Sustained Engineering in Spotlight