Systems software on microcomputers: Which of the following are examples of operating system or system-level software commonly used on microcomputers (personal computers)?

Introduction / Context:
System software is the foundational software that manages hardware resources, provides core services, and offers an interface for application software. On microcomputers, classic examples include various disk operating systems and Unix-like operating systems. This question checks recognition of standard system software used historically and presently on PCs.

Given Data / Assumptions:

• The platforms referenced are microcomputers (personal computers).
• MS-DOS and PC-DOS are DOS-family operating systems.
• Unix is a multiuser, multitasking operating system family with PC ports and derivatives.

Concept / Approach:

System software includes the operating system (OS), device drivers, utility programs closely tied to hardware, and firmware interfaces. MS-DOS (by Microsoft) and PC-DOS (by IBM) were widely used on early IBM PC-compatible systems. Unix and its variants (including modern Unix-like systems) have also run on microcomputers, providing multitasking, multiuser capabilities, and rich networking stacks.

Step-by-Step Solution:

Verification / Alternative check:

Historical PC documentation lists MS-DOS/PC-DOS as default OSes on IBM PCs and compatibles. Numerous PC ports of Unix (e.g., Xenix, BSD variants, SCO, and later Unix-like systems) demonstrate Unix as system software on microcomputers.

Why Other Options Are Wrong:

• MS-DOS, PC-DOS, Unix (individually): Each is correct but incomplete; the question asks which are examples, and all are.
• None of the above: Incorrect because all listed are valid examples.

Common Pitfalls:

Confusing application software (word processors, spreadsheets) with system software; assuming Unix is only for mainframes or servers (it also exists on PCs).

Final Answer:

All of the above