The best IITM qualifier Computational Thinking PYQ set to practise is the four official CT qualifier papers: May 2023, September 2023, January 2024 and May 2024. Each has 12 to 14 questions worth 50 marks, and each comes with the official answer key. You can sit all four free on BTechi in a timed exam portal, or download each one as a free CT qualifier PYQ PDF with the answer key.
This post goes one step further. We sorted all 54 questions from those papers by what they ask you to do, then solved seven real ones and checked every answer against the official key.
New to the qualifier itself? Read our IITM BS qualifier exam guide first. It covers the cut-offs, fees and the four-week process.
Why CT decides so many qualifier results#
The qualifier has four courses: Maths I, Stats I, Computational Thinking (CT) and English I. A General-category candidate needs at least 40% in every course and at least 50% on average (official admissions page). So one weak course can fail you, even with a high average.
CT is often that weak course. It looks easy because there is no real programming language. But it tests exact tracing: follow pseudocode line by line and track every variable. One > read as >=, and the answer changes.
The CT qualifier syllabus is the first four weeks of the course (official course page):
- Variables, iteration and filtering
- Datasets as cards and tables
- Flowcharts and pseudocode
- Procedures and multiple filters
IITM qualifier CT PYQ papers: where to find them#
Here is every CT paper on BTechi. The quiz and end-term papers cover the full course, but they use the same datasets and loop patterns, so they are good extra practice.
You can also see all of them on the Computational Thinking PYQ page, or start a qualifier-only drill from CT qualifier practice.
Printable CT question sheets#
If you like to solve on paper, use the printable sheets. Each one is a real IIT Madras qualifier previous year question paper PDF for CT: click Save PDF on the sheet to download it with the answer key.
- CT 2023 question sheet (May and September 2023 qualifiers)
- CT 2024 question sheet (January and May 2024 qualifiers, plus the December 2024 end term)
- CT 2025 question sheet (2025 quizzes and end terms)
- All CT sheets, and sheets for every course on the PYQ sheets page
Download IITM qualifier Computational Thinking PYQ PDF#
- Open the question sheet of the paper you want (links below).
- Click the Save PDF button at the top of the sheet. You can also press P on your keyboard.
- In the print window, choose Save as PDF as the destination, then save.
The PDF has every question and figure, and the official answer key at the end. It is free. Print it, or keep it on your phone or tablet.
CT questions are full of pseudocode and dataset cards, so a printed PDF is easier to trace with a pen. Each CT qualifier paper as a PDF:
- CT qualifier May 2024 PDF with answer key
- CT qualifier January 2024 PDF with answer key
- CT qualifier September 2023 PDF with answer key
- CT qualifier May 2023 PDF with answer key
What the CT qualifier papers ask: 54 questions sorted#
BTechi tags Maths, Stats and English questions by topic, but CT is not tagged yet. So we counted by hand. We read all 54 questions in the four qualifier papers and put each one in the group that best matches its task.
The lesson: reading code matters more than writing it. 37 of 54 questions give you the code (or most of it) and ask what it means. Practise saying, in one plain sentence, what a loop counts. Tracing is the tool; explaining is the goal.
Question formats and marks#
MSQ and NAT together carry 91 of 200 marks. That is almost half. In these formats you cannot guess from four options, so careful tracing pays the most here.
The datasets you must know#
CT questions are built on datasets shown as cards. Learn their fields before you open a paper. Here is where each one appeared:
Patterns that repeat across papers#
Some questions come back almost word for word. These are the most important CT questions for the qualifier:
- The same Library question twice. May 2023 Q4 and January 2024 Q3 use the same pseudocode and the same four options (solved below).
- The miniSum procedure twice. September 2023 and January 2024 both ask you to complete a procedure that returns the sum of the two smallest of three numbers.
- The same Words paragraph twice. January 2024 Q16 and May 2024 Q13 use the same paragraph with a small change in the code. The answers are different (solved below).
- "Same gender or same city" pairs. May 2023 Q16, January 2024 Q15 and May 2024 Q14 all count pairs of students by gender and city, with "or", "but not both", or "both or neither".
- Pairs of cards in general. 9 of the 54 questions count pairs of rows with a nested loop, and 2 more use the same loop shape to find repeated words.
- Vowel counting in Words. Count vowels, find vowels in a row, or compare vowel counts of two words. It appears in every paper.
- Ties. Many "max" and "which is bigger" questions hinge on what happens when two values are equal.
Solved IITM qualifier CT PYQs (checked against the official key)#
Each example below is a real question. We give the code in text form, the working, and the official answer.
Example 1: the Library question that appeared twice (May 2023 and January 2024)#
The pseudocode runs on the Library dataset:
A = 0
count = 0
while (Table 1 has more rows) {
Read the first row X in Table 1
count = count + 1
if (X.Author != "Kalam" and X.Language != "English") {
A = A + 1
}
Move X to Table 2
}
B = count - AWhat does B represent?
countis the total number of books.- A counts books that are not by Kalam and not in English.
- So
count - Ais every other book: books by Kalam, or in English, or both.
Official answer: number of books written by Kalam or in English or both.
The idea behind it is De Morgan's law: "not (P or Q)" is the same as "not P and not Q". When you see total - (count of not P and not Q), the answer is "P or Q".
Example 2: tracing a procedure with ties (May 2024 Q12, NAT)#
Procedure mSum(A, B, C)
Sum = 0
if (A >= C and A >= B) {
Sum = B + C
}
else {
if (B >= C and B >= A) {
Sum = A + C
}
else {
Sum = A + B
}
}
return(Sum)
End mSumWhat is mSum(4, 4, 2)?
- A = 4, B = 4, C = 2.
- First check: is 4 >= 2 and 4 >= 4? Yes, both are true (the
>=allows the tie). - So Sum = B + C = 4 + 2 = 6.
Official answer: 6. The procedure adds the two numbers other than the largest. Now see why >= matters. If you read it as >, the first check fails (4 > 4 is false), the second check also fails (4 > 4 again), and you land on Sum = A + B = 8. That wrong answer is exactly what a careless reading gives.
Example 3: same paragraph, different answer (January 2024 Q16 and May 2024 Q13)#
Both questions use a Words-style dataset made from this paragraph:
"Surrounded by nature, Susan often takes a stroll, savoring the soothing sounds of chirping birds. Rustlings in the trees suggest squirrels beginning their day, searching for sustenance. Surely, the beauty of a sunrise holds unparalleled magic."
The January 2024 paper adds one more sentence after "birds.": "Such moments underline the significance of embracing simple joys in life." Both codes count words whose first two letters are "su", but only when flag is True.
January 2024 version:
count = 0, flag = True
while (Table 1 has more rows) {
Read the first row X in Table 1
Move X to Table 2
if (flag) {
if (1st letter of X.Word == 's') {
if (2nd letter of X.Word == 'u') {
count = count + 1
}
}
}
flag = False
if (X.Word ends with full stop) {
flag = True
}
}Here flag is True only for the first word, and for any word right after a full stop. So the code counts sentences whose first word starts with "su": Surrounded, Such, Surely. Rustlings does not count.
Official answer: 3.
May 2024 version: the code starts with flag = True and only has if (X.Word ends with full stop) { flag = False }. Nothing ever sets it back to True. So it only checks words in the first sentence: Surrounded and Susan. "Soothing" and "sounds" start with "so", not "su".
Official answer: 2.
The trap: Susan, suggest, sustenance and sunrise are all in the paragraph. Count every "su" word without reading the flag logic, and both answers are wrong.
Example 4: the digit loop (May 2023 Q12, NAT)#
r = 0, s = 0, n = 1024
while (n > 0) {
r = n % 10
s = s + r
n = n // 10
}% gives the remainder and // gives the quotient. Trace it in a table:
The loop stops when n = 0. Official answer: 7, the sum of the digits.
A close cousin from the same paper (Q13): A starts at 1 and doubles for every vowel in the word "aeroplane". The vowels are a, e, o, a, e, so A = 2⁵ = 32, which matches the key.
Example 5: the tie that decides the answer (September 2023 Q7)#
A company has this data on how many people will come to a promotion:
The procedure bestDay(Z) adds the Saturday and Sunday numbers for city Z. Then if (countSun >= countSat) it returns "Sunday", else "Saturday".
- Lucknow: Saturday 30 + 20 = 50, Sunday 50 + 50 = 100. Returns Sunday.
- Chennai: Saturday 20 + 30 = 50, Sunday 30 + 20 = 50. A tie, and
>=is true, so it returns Sunday.
Official answer: bestDay("Lucknow") = "Sunday" and bestDay("Chennai") = "Sunday". The option with Chennai = "Saturday" catches everyone who skips the tie.
Example 6: find the bug (September 2023 Q12, MSQ)#
The code should find the highest item price from Big Bazaar bills in the Shopping Bills dataset. The helper procedure is:
Procedure findItem(Y)
maxPrice = 0
while (Card Y has more items) {
Read an item Z from ItemList of card Y
if (maxPrice >= Z.Price) {
maxPrice = Z.Price
}
Remove Z from ItemList of card Y
}
return(maxPrice)
End findItemLook at the if. It updates maxPrice when the current max is bigger than the new price. That is backwards. With maxPrice = 0 and positive prices, it never updates and always returns 0. The correct condition is Z.Price > maxPrice.
The other options blamed line 5 (calling the procedure), line 6 (the outer temp > A check, which is correct), and a missing reset of maxPrice. None of those are errors.
Official answer: only line 16, "Incorrect conditional statement".
Example 7: counting pairs (May 2024 Q14)#
This is the pattern behind 9 of the 54 questions. The outer loop takes a card X and moves it to Table 2. The inner loop compares X with every card Y still in Table 1, then moves them back. The figure shows why this visits every pair exactly once.
In May 2024 Q14, each pair goes to this procedure on the Scores dataset:
Procedure findPair(X, Y)
A = False, B = False
if (X.Gender == Y.Gender) { A = True }
if (X.CityTown == Y.CityTown) { B = True }
if ((A and B) or (not A and not B)) { return(1) }
return(0)
End findPairA means "same gender" and B means "same city". The condition is true when both are true or both are false.
Official answer: count is the number of student pairs who share the same gender and the same city, or who share neither.
Compare this with the May 2023 and January 2024 versions, which ask for "same gender or same city but not both". That is exactly the opposite case: A and B have different values. Learn the four combinations once, and all three questions become easy:
How to practise CT PYQs: a 4-paper plan#
Four papers is not a lot, so use them well. This plan fits the last two weeks before the exam.
- Week 3, paper 1 (untimed). Do the May 2023 CT paper with a pen and paper. Write a trace table for every question, even the easy ones. Check against the key.
- Week 3, paper 2 (untimed). Do September 2023. For every wrong answer, write one line: what did you misread?
- Week 4, paper 3 (timed). Do January 2024 under a timer. BTechi sets each CT paper to 60 minutes.
- Week 4, paper 4 (inside a full mock). Sit the full May 2024 qualifier paper with all four courses in one go. This shows if your CT accuracy holds when you are tired.
- Extra practice. Use the CT Quiz 1 October 2025 paper, then mock qualifier 1 and mock 2 for full timed runs.
The other full four-course papers are May 2023, September 2023 and January 2024. Our CT cheat notes list every loop pattern with its trap, for your last-week revision.
Common CT traps in the qualifier#
These traps showed up again and again in the 54 questions:
- Ties, flags, reversed conditions and "but not both". See Examples 2, 3, 5, 6 and 7 above.
- Forgetting to move rows back. In pair loops, if Table 3 is not moved back to Table 1, the next round has nothing to compare.
- Initial values. A max must start at a value that cannot beat the real maximum. September 2023 Q9 asks how to start
maxfor the highest total. The key accepts three options: the total of a random card, the total of the top card, or any value below the lowest possible total. Starting above the highest possible total is wrong, because no card can ever replace it. - Data types and ranges. In data sanity questions, a card number written as "xyz", a Word stored as the number 1, and a letter count of −5 are all wrong (January 2024 Q14).
Where CT fits in your qualifier preparation#
You need 40% in CT no matter how well you do elsewhere. Use the other posts in this series to plan all four courses:
- IITM qualifier English important questions
- IITM qualifier Maths important questions
- IITM qualifier Stats important questions
- Every IITM qualifier previous year paper with answer key
If you are still deciding whether to apply, see our IIT Madras BS admission guide for January 2027. Applications for the January 2027 batch close on 29 January 2027. The official IIT Madras BS Data Science site has the current dates.
Frequently asked questions#
Where can I download the IITM qualifier Computational Thinking PYQ PDF for free?#
On BTechi. Open any CT question sheet, click Save PDF (or press P) and choose Save as PDF. The PDF is free and has the official answer key at the end. The download section links every CT qualifier paper.
How many questions are in the CT qualifier paper?#
The four CT qualifier papers on BTechi have 12 to 14 questions each, and each paper is worth 50 marks. Across the four papers there are 54 questions: 31 MCQ, 18 MSQ and 5 numerical answer questions.
Do CT qualifier questions repeat?#
Yes, sometimes almost exactly. The Library "Kalam or English" question appeared in both May 2023 and January 2024, the miniSum procedure in September 2023 and January 2024, and the same Words paragraph in January 2024 and May 2024. The pattern of counting pairs of students by gender and city appeared in three papers.
Which topics are most important for CT in the IITM qualifier?#
Reading and completing pseudocode on the Scores, Words and Library datasets. These three datasets appeared in all four papers. Within them, focus on filters with "and" and "or", counting pairs with nested loops, vowel counting in words, and procedures with if-else chains.
Is there negative marking in the CT qualifier?#
The marking rules are given in the exam instructions for your term. Read them on the day and in your hall ticket. The BTechi practice portal follows the official answer key for scoring.
Do I need to know programming for the CT qualifier?#
No. CT uses pseudocode, not a real programming language. But you need the habit of tracing code line by line. Python comes later, in the Foundation level.
How long should I spend on each CT paper?#
BTechi times each CT paper at 60 minutes for practice. In the real qualifier, you share four hours across all four courses, so practise at least one full four-course qualifier paper to plan your time.