In character encoding using ASCII (American Standard Code for Information Interchange), adding a 0 to the leftmost (most significant) bit to form an 8-bit byte from a 7-bit character is called ________.

Introduction / Context:
ASCII is historically a 7-bit code. In many digital systems, bytes are 8 bits wide, so a 7-bit ASCII character is commonly stored in an 8-bit location by adding an extra bit on the left. This question asks for the proper term used when a 0 is added to that most significant position to fill the byte neatly without changing the character value.

Given Data / Assumptions:

• ASCII characters are 7 bits in their original definition.
• Storage and transmission often use 8-bit bytes.
• The added bit is placed in the most significant position (leftmost bit).
• The added bit is 0, not 1.

Concept / Approach:
When extending a binary value to a wider width without changing its magnitude, adding zeros to the left (high-order side) is called “zero padding” or “zero extension.” This preserves the numeric/encoded meaning and is distinct from adding a parity bit or performing sign extension (used with signed integers).

Step-by-Step Solution:

Verification / Alternative check:
Compare numerical values before and after: 1000001 (binary 65) becomes 01000001 (binary 65). The value is identical, confirming a padding (not a reinterpretation).

Why Other Options Are Wrong:

• Sign extension: Copies the sign bit (1 for negative in signed integers), not applicable to ASCII characters.
• Parity insertion: Adds a parity bit for error detection, typically separate from the stored character byte.
• MSB masking: Refers to clearing or ignoring the MSB using a mask, not adding a new bit.
• Bit stuffing: Protocol-level addition of bits in streams to avoid reserved patterns, not fixed-width padding.

Common Pitfalls:
Confusing parity with padding; assuming sign rules apply to character encodings; thinking the added bit changes the code point. It does not; it merely fits the code into an 8-bit container.

Final Answer:
zero padding