OpenBSD: An OS that works on the mantra of Security. OpenBSD will not add anything unless it is completely sure of its security, unlike other OS that looks at security as a feature of performance. It checks the database for vulnerabilities and has made modifications to C library that helps prevent buffer overrun of programs.

OpenBSD was the first non-research OS to integrate many features, which puts libraries and memory sections in random locations in RAM, that way no crackers can't assume their location.

KolibriOS: Earlier OS used to be written in assembly language though it is not so in modern OS.  Programming in assembly is hard work, but it can often lead to results that a typical compiler cannot compete with. KolibriOS, a part of MenuetOS, is written entirely in assembly language.

They best part is that it's tiny (4.9MB for the ISO) and ridiculously fast (booting in a couple of seconds). Apart from these features, it includes a web browser, mail client, games, and more, all running at light speed. This OS is nowhere near Windows but it sure is free of bloat and wastefulness we are used to.

AROS: This particular computer Os used to be loved by many people before and it still has many fans. It had amazing graphics, crisp sounds and it was great at multitasking. AROS is a word made of the first letters of Amiga Research Operating Systems.

This OS was super fast and it can be revived with little changes to the old Amiga OS and can be used with great compatibility for low level netbooks and tablets.

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