8086/8088 segment registers — identify the invalid name Which of the following is NOT a valid segment register name in the 8086/8088 architecture?

Introduction / Context:
The 8086/8088 memory model is built around segment:offset addressing with distinct segment registers. Recognizing correct register names helps in reading assembly and understanding how memory is partitioned.

Given Data / Assumptions:

• 8086/8088 segment registers include CS, DS, SS, and ES (extra segment).
• No register named “AS” exists.

Concept / Approach:
By comparing the offered names with the canonical set, we can quickly identify the imposter. “Address segment (AS)” is not part of the x86 register file.

Step-by-Step Solution:
List actual segment registers → CS, DS, SS, ES.Scan options → CS, DS, SS are valid; “AS” is unknown.Select the invalid name → Address segment (AS).

Verification / Alternative check:
Any 8086/8088 programming reference confirms the four segment registers above; later x86 added FS and GS, still no “AS.”

Why Other Options Are Wrong:
CS, DS, SS are all standard and essential to 8086/8088 operation.

Common Pitfalls:
Confusing “address” as a generic term with a specific register name; “address” is a function, not a register label.

Final Answer:
Address segment (AS)