In the context of 8086-style segmented memory addressing in C (for example, Turbo C on DOS), how can you obtain the segment and offset parts from a far pointer that holds the address of a memory location?

Introduction / Context:
On older x86 real-mode systems such as DOS, memory was addressed using segment:offset pairs. Compilers like Turbo C supported near, far, and huge pointers to work within this segmented memory model. A far pointer internally stored both the segment and offset parts of an address. Many low-level or systems programming tasks required extracting these individual components.

Given Data / Assumptions:

• We are working in a 16-bit segmented memory model such as 8086 real mode.
• A far pointer holds both a 16-bit segment and a 16-bit offset.
• The question asks how to obtain segment and offset from such a far pointer in C.
• We assume we are using a DOS-era compiler like Turbo C that provides helper macros.

Concept / Approach:
In these compilers, a far pointer is represented as a 32-bit quantity, with the high 16 bits holding the segment and the low 16 bits holding the offset. Instead of manually shifting and masking bits, the runtime library usually provides macros to extract these parts safely. Turbo C, for example, defines FP_SEG(ptr) to return the segment part and FP_OFF(ptr) to return the offset part of a pointer. Using these macros is the standard and portable way, within that environment, to access the underlying segment and offset.

Step-by-Step Solution:
Step 1: Declare a far pointer, for example char far *p, that points to a memory location.Step 2: Use the macro FP_SEG(p) to obtain the 16-bit segment value associated with p.Step 3: Use the macro FP_OFF(p) to obtain the 16-bit offset value associated with p.Step 4: These macros internally perform the correct shifts and masks based on the compiler representation of far pointers.Step 5: The resulting segment and offset can then be used for interrupt calls, hardware programming, or debugging displays.

Verification / Alternative check:
Turbo C reference manuals and header files demonstrate these macros and their usage. Sample code often shows printf("%X:%X", FP_SEG(p), FP_OFF(p)); to print a segment:offset address. The macros are widely used in legacy DOS code, confirming that this is the idiomatic way to obtain the components from a far pointer.

Why Other Options Are Wrong:
Option B suggesting dividing by 10 has no basis in how segments and offsets are encoded; segment calculations involve multiples of 16, not 10. Option C incorrectly describes the transformation; far pointers are not manipulated by simple multiplication to obtain segments and offsets. Option D is wrong because compilers explicitly expose segment and offset through FP_SEG and FP_OFF, so it is definitely possible.

Common Pitfalls:
Programmers sometimes try to rely on assumptions about pointer representation and manually shift or cast values. This is error prone and non-portable even across compilers targeting the same hardware. Another pitfall is forgetting that modern protected-mode and 64-bit environments do not use segment:offset addressing the same way, so FP_SEG and FP_OFF are obsolete outside of legacy DOS programming.

Final Answer:
You can obtain the segment and offset from a far pointer by using FP_SEG(pointer) to get the segment and FP_OFF(pointer) to get the offset.