Which category of software is protected by copyright laws but is available at no cost?

Closed-source software is characterized by restricted access to its source code, meaning users cannot view or modify it. While it can be free or paid, closed-source software is not inherently available at no cost; many closed-source programs require a purchase or subscription. Therefore, it does not fit the definition of being freely available.

Public domain software is not protected by copyright laws, meaning it can be freely used, modified, and distributed by anyone without restrictions. This category differs from freeware, as public domain software does not carry any copyright protections, making it available without the legal limitations that apply to freeware.

Shareware typically allows users to try the software for free for a limited time or with limited features, but it generally requires payment for continued use or access to the full version. Unlike freeware, shareware is not fully free and often involves a licensing fee, which means it does not meet the criteria of being available at no cost while still being copyright-protected.