7447 BCD-to-seven-segment decoder: which segments light for the digit “1”? For a 7447 code converter driving a common-anode display, which segments are active to display the numeral 1?

Introduction / Context:
Understanding standard seven-segment coding is essential for designing front-panel displays, debugging instrument readouts, and writing HDL driving logic. The TTL 7447 is a classic BCD-to-seven-segment decoder for common-anode LEDs.

Given Data / Assumptions:

• IC: 7447 BCD-to-seven-segment decoder/driver.
• Target digit: decimal 1.
• Common-anode display (7447 outputs are active-LOW).

Concept / Approach:
A seven-segment display uses segments a through g. For the digit “1,” only segments b and c should illuminate. With the 7447 and a common-anode LED, the decoder pulls b and c LOW (active-LOW), while other outputs remain HIGH (off).

Step-by-Step Solution:

Verification / Alternative check:
Check a segment truth table from a datasheet or memorize common patterns: 0 (a,b,c,d,e,f), 1 (b,c), 2 (a,b,d,e,g), 3 (a,b,c,d,g), etc.

Why Other Options Are Wrong:

• a only / b only / a and b: None match the standard “1” pattern, which always requires b and c together.

Common Pitfalls:

• Mistaking common-anode for common-cathode: the 7447 uses active-LOW outputs, but the lit segments for a given digit are the same logical set (polarity just inverts the drive).

Final Answer:
Segments b and c are active.