Device drivers in CONFIG.SYS: What operation does the HIMEM.SYS driver perform in DOS/Windows 9x environments?

Introduction / Context:
Legacy DOS systems load device drivers via CONFIG.SYS to extend capabilities. HIMEM.SYS is a well-known driver that enables the system to address memory above 1 MB using the CPU’s protected-mode features exposed through XMS (Extended Memory Specification).

Given Data / Assumptions:

• You are configuring memory management in DOS/Windows 9x.
• HIMEM.SYS is referenced in CONFIG.SYS (e.g., DEVICE=HIMEM.SYS).
• You need extended (XMS), not expanded (EMS) memory services.

Concept / Approach:
HIMEM.SYS is the XMS manager. It provides access to extended memory and the High Memory Area (HMA), enabling loading portions of DOS and drivers high to free conventional memory. EMS (expanded memory) is managed by EMM386.EXE, a different component that uses paging to simulate EMS on 80386+ CPUs. ANSI terminal emulation is handled by ANSI.SYS; code page switching by DISPLAY.SYS/KEYB and related utilities.

Step-by-Step Solution:

Verification / Alternative check:
Use MEM /C or diagnostic tools to confirm XMS availability after loading HIMEM.SYS; observe that EMS requires EMM386.EXE.

Why Other Options Are Wrong:
ANSI emulation: ANSI.SYS does this. Expanded memory on 80386: handled by EMM386.EXE, not HIMEM.SYS. Code page switching: handled by DISPLAY.SYS/KEYB.

Common Pitfalls:
Confusing extended and expanded memory; forgetting that both HIMEM.SYS and EMM386.EXE may be used together for different purposes.

Final Answer:
Manages the use of extended memory