Concept check: What is the key difference between generic binary coding and binary-coded decimal (BCD) when representing numeric data?

Introduction / Context:
There are multiple ways to represent decimal numbers inside digital systems. Pure binary coding represents the entire numeric value as a single base-2 quantity. Binary-coded decimal (BCD), on the other hand, encodes each decimal digit separately using a 4-bit nibble. Understanding this distinction affects arithmetic design, storage efficiency, and user-interface formatting choices.

Given Data / Assumptions:

• Pure binary uses powers of 2 for the entire number.
• BCD uses 4-bit nibbles for digits 0 through 9.
• We consider standard straight BCD (8421).

Concept / Approach:
In pure binary, a value like 59 is stored as 00111011₂ (one quantity). In BCD, 59 is stored as two nibbles: 0101 (five) and 1001 (nine), often packed into one byte as 0x59. BCD eases decimal digit extraction and display, while pure binary is more storage efficient and supports native binary arithmetic without digit-wise constraints.

Step-by-Step Solution:

Verification / Alternative check:
Consider the number 99: pure binary uses 7 bits (1100011₂), while BCD uses two nibbles 1001 1001 (8 bits). This illustrates BCD's overhead and its convenience for decimal display and financial calculations.

Why Other Options Are Wrong:

• BCD is pure binary: False; BCD is a decimal-digit-oriented code using binary symbols but not a pure binary representation of the whole number.
• Binary coding has a decimal format: Incorrect; pure binary is base 2.
• BCD has no decimal format: Incorrect; BCD is explicitly a decimal digit format.

Common Pitfalls:
Confusing BCD with a different base, assuming arithmetic works the same as binary (BCD arithmetic needs digit corrections like adding 6 in some adders), and forgetting invalid BCD codes 1010–1111.

Final Answer:
Binary coding is pure binary.