Bihar STET Computer Science: Questions the Board Has Already Repeated
Most exams avoid repeating questions. The Bihar STET Computer Science paper does the opposite: when we compared the four November 2025 shifts with the 2023 paper, every shift had between 7 and 16 questions that had already appeared, often with the same four options in the same order. This guide lists the most useful of them with the correct answer — and flags the ones where the board's own answer key disagrees with the textbook.
In this guide
Key takeaways
- 7 to 16 repeated Computer Science questions in every 2025 shift.
- Repeats come mostly from software engineering, OOP, digital logic, operating systems and networks.
- Some official keys differ from the textbook: K-maps, ARP, context-free language closure, WSN and staffing estimation.
- Learn both the textbook answer and the key's answer for those questions.
How we found the repeats
We extracted the text of all 500 Computer Science questions from the five papers and compared every pair of questions from different papers. Where the wording matched closely, we read both questions to confirm that they were the same question and not just a similar opening line. Look-alike questions with different content — "the term FAT" and "the term DFD", for example — were removed.
Repeated questions with answers
Software engineering and OOP
| Question | Answer | Seen in |
|---|---|---|
| The term "DFD" stands for | Data flow diagram | 2023, 3 Nov S1, 7 Nov S1 |
| Main purpose of inheritance in OOP | A parent–child relationship (code reuse) | 2023, 3 Nov S1, 3 Nov S2 |
| Keyword to create an instance of a class | new | 2023, 7 Nov S1 |
| Testing individual units of code | Unit testing | 2023, 3 Nov S1 |
| Reverse engineering is used for | Understanding and documenting existing software | 2023, 3 Nov S2 |
| Purpose of a constructor | To initialise the object's properties | 3 Nov S1, 3 Nov S2 |
Digital logic and organisation
| Question | Answer | Seen in |
|---|---|---|
| Components used in a PLA | AND gates and OR gates | 2023, 7 Nov S1 |
| Gray code to binary uses | Exclusive-OR (XOR) | 2023, 4 Nov S2 |
| Register that holds data during ALU operations | Accumulator | 2023, 7 Nov S1 |
| Width of the data bus is measured in | Bits | 2023, 3 Nov S1 |
Operating systems, algorithms and theory
| Question | Answer | Seen in |
|---|---|---|
| A buffer cache is used to | Keep copies of frequently used disk blocks in memory | 2023, 7 Nov S1 |
| T(n) = T(n/2) + 1 represents | Divide and conquer (binary search, O(log n)) | 2023, 7 Nov S1 |
| Separate chaining stores collided keys in | Linked lists | 2023, 7 Nov S1 |
| A language for which a DFA exists | Regular language | 2023, 3 Nov S1 |
| DFA for binary numbers divisible by 3 — states | 0, 1, 2 (the remainders) | 2023, 4 Nov S2 |
| NFA of 5 states plus the initial state, maximum DFA states | 2⁶ = 64 | 2023, 3 Nov S1 |
Networks, web and IoT
| Question | Answer | Seen in |
|---|---|---|
| Not a network topology | Disk | 2023, 3 Nov S1 |
| Contention-based MAC protocols are used in | Ethernet | 2023, 3 Nov S1 |
| Protocol for sending email | SMTP | 2023, 7 Nov S1 |
| CSS stands for | Cascading Style Sheets | 2023, 4 Nov S2 |
| XML attribute that uniquely identifies an element | id | 2023, 4 Nov S2 |
| MISO pin of an RFID module | Master In Slave Out | 2023, 3 Nov S1 |
| Not true about IoT | "IoT is fully safe" | 2023, 3 Nov S2 |
Where the official key differs from the textbook
These questions were repeated with the same key. Learn the correct answer — it is what the subject teaches — and remember the key's answer, because a word-for-word repeat is likely to be marked the same way.
| Question | Textbook answer | Board's key |
|---|---|---|
| Simplify F(A,B,C,D) = Σ(0,1,2,4,5,6,8,9,10,12,13,14) | C′ + D′ (only minterms 3, 7, 11, 15 are missing) | A long five-term expression (option 1) |
| SOP of F(A,B,C) = Σ(0,1,2,3,5) | A′ + B′C | A′B′ + AB′ + AB + AC |
| Simplify F(A,B,C) = Σ(0,1,3,5) | A′B′ + A′C + B′C | A′B + AC |
| Purpose of ARP | Find the MAC address for an IP address | "Map MAC addresses to IP addresses" (the only mapping option) |
| Context-free languages are not closed under | Intersection (and complement) | Repeated concatenation |
| WSN stands for | Wireless sensor network | Wireless sensor protocol (no "network" option) |
| Purpose of staffing level estimation | Allocating people and resources | Identifying potential risks |
The K-map questions are worth a minute of checking in the exam. In the first one, the twelve minterms leave out exactly the four with C = 1 and D = 1, so the function is 1 whenever C or D is 0 — that is C′ + D′. None of the options shows this, which is why the key's choice looks strange.
Why repeats happen, and what that means for you
A large exam held across several shifts needs hundreds of new questions, and question banks are often reused. Whatever the reason, the effect for a candidate is clear: the earlier papers are not just practice material, they are part of the next paper. That also means the repeated questions reward exact reading. A repeated question may keep its options but change their order, or turn a "which is" into a "which is not". Read every question in full even when it looks familiar, and match the answer by its words, not by its position in the list.
How to use this list
- Read it the night before the exam. It takes ten minutes.
- Answer repeats first. When you recognise a question, answer it at once and move on.
- Do not over-think familiar questions. If it matches the list word for word, the earlier answer is your guide.
- Keep studying the units. Repeats are a bonus of 7 to 16 marks; the rest of the paper still decides your result.
The full topic counts behind this list are in our previous year papers analysis, and the marks you need to pass are explained in our passing marks guide. For how to fit this list into your revision, see the preparation strategy.
Finally, keep the list in proportion. Recognising a repeat saves time and secures a mark, but a candidate who has only memorised this list will still face eighty or more unfamiliar questions. Use it as the last layer of preparation, on top of the units themselves.
Summary
- Each 2025 shift repeated 7 to 16 questions from 2023.
- DFD, inheritance, PLA, Gray code, buffer cache and SMTP are among the repeats.
- Seven repeated questions have unusual keys — learn both answers.
- Revise the list last, and answer recognised questions first.
Frequently asked questions
How many questions does Bihar STET repeat?
In the four November 2025 shifts we compared with the 2023 paper, each shift contained between 7 and 16 Computer Science questions that had appeared almost word for word before. With no negative marking, recognising these questions quickly is close to free marks.
What should I do if the official answer key looks wrong?
Learn the textbook answer, because that is what the subject is, but also note the answer the board's key accepted. If the same question returns word for word, the earlier key is the best guide to what will be marked correct. You can also raise an objection when the provisional key is published.
Which repeated question appeared most often?
The full form of DFD, data flow diagram, appeared in 2023 and in two 2025 shifts. The purpose of inheritance in object-oriented programming also appeared three times. Both are software and programming basics that take seconds to answer.
Are repeated questions only from Computer Science?
This list covers the Computer Science part. The Teaching Art part repeats ideas rather than exact wording, such as microteaching, Bloom's taxonomy, Piaget's stages and the Right to Education Act, so it is better prepared from a fact list than from exact questions.
Sources
Dates, the pattern and pass marks are set by BSEB and can change. Always confirm at biharboardonline.bihar.gov.in. GATE Guide is not affiliated with BSEB.