This PCEP practice question tests your understanding of data types, variables, basic i/o and operators. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer uses bitwise operators to set flags for packet filtering. The variable 'flags' currently holds the integer 10 (binary 1010). To enable the second bit (value 2) and disable the fourth bit (value 8), which expression should be used?
flags = flags | 2
Why wrong: Only sets the second bit, does not clear the fourth
flags = flags ^ 10
Why wrong: XOR toggles bits, not the desired operation
flags = flags & ~8
Why wrong: Only clears the fourth bit, does not set the second
flags = (flags | 2) & ~8
Correctly sets bit 1 and clears bit 3
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
flags = (flags | 2) & ~8
Option D is correct because it combines two operations in a single expression: first, it sets the second bit (value 2) using the bitwise OR (|) operator, which turns on that bit without affecting others; second, it clears the fourth bit (value 8) using the bitwise AND with the complement of 8 (& ~8), which forces that bit to 0. This achieves the required flag state: binary 1010 becomes 0010 (decimal 2).
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
flags = flags | 2
Why it's wrong here
Only sets the second bit, does not clear the fourth
flags = flags ^ 10
Why it's wrong here
XOR toggles bits, not the desired operation
flags = flags & ~8
Why it's wrong here
Only clears the fourth bit, does not set the second
flags = (flags | 2) & ~8
Why this is correct
Correctly sets bit 1 and clears bit 3
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Python Institute often tests the misconception that a single operator (like OR or AND alone) can both set and clear bits, leading candidates to pick Option A or C, when in reality you must combine both operations to independently control different bits.
Detailed technical explanation
Bitwise operations are fundamental in low-level network programming, such as setting TCP flag bits (e.g., SYN, ACK) or configuring packet filter rules in iptables or nftables. The expression (flags | 2) & ~8 works because bitwise OR sets specific bits to 1, while bitwise AND with a complement clears specific bits; the order matters because OR is performed first, ensuring the second bit is set before clearing the fourth. A subtle behavior is that if the same bit is both set and cleared in the same expression, the OR operation takes precedence when combined with AND, but here the bits are distinct, so no conflict arises.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the PCEP exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Data Types, Variables, Basic I/O and Operators — This question tests Data Types, Variables, Basic I/O and Operators — Read the scenario before looking for a memorised answer..
The correct answer is: flags = (flags | 2) & ~8 — Option D is correct because it combines two operations in a single expression: first, it sets the second bit (value 2) using the bitwise OR (|) operator, which turns on that bit without affecting others; second, it clears the fourth bit (value 8) using the bitwise AND with the complement of 8 (& ~8), which forces that bit to 0. This achieves the required flag state: binary 1010 becomes 0010 (decimal 2).
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This PCEP practice question is part of Courseiva's free Python Institute certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCEP exam.
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