ISRO Scientist CS Exam Pattern 2026: CBT and Interview

The ISRO Scientist CS exam pattern has two stages: a 100-mark computer based test (CBT) and a 100-mark interview. The CBT itself has two parts, a Computer Science paper and an aptitude paper, and each part has its own minimum qualifying mark. Final merit gives equal weight to the CBT and the interview.

This page follows Advertisement No. ISRO:ICRB:03(EMC):2026 and explains what the numbers mean for your time and accuracy. For topics, see the ISRO Scientist CS syllabus.

Table of Contents

Pattern at a glance

Stage 1: Computer based test

The advertisement states "maximum 15" questions for Part B's 20 marks, so Part B questions do not all carry equal marks and the exact split is not given. Read the on-screen instructions on test day to see how the parts are timed and whether you can move between them.

The test is held at 37 venues across India, and ISRO may change venues. The test centre cannot be changed after the application is submitted. No travel allowance is paid for the written test.

Qualifying marks

You must score the minimum in each part separately. A high score in Part A does not make up for a low score in Part B.

For a full-length paper, 50% means 40 marks in Part A and 10 marks in Part B. Meeting the minimum only makes you eligible for shortlisting. Candidates are then shortlisted for the interview in a ratio of 1:5 (with a minimum of 10 candidates) on the basis of their written test performance, so the real competition is for rank.

Marking scheme and negative marking

Answer keys are published within three working days of the test. Objections must be raised within five days of publication and only through the official link.

What the pattern means for you

• Part A is 80% of the paper: One mark per question means every careless slip in Part A hurts more than a missed Part B question.

• Blind guessing does not pay: With four options, a random guess has an expected gain of zero, since a one-in-four chance of +1 is cancelled by a three-in-four chance of minus 1/3. Guess only after removing at least one option. (Previous ISRO papers have used four options per question.)

• Part B is a free zone: There is no penalty, so attempt every Part B question. Your risk is not wrong answers but missing the 50% minimum.

• Time per question differs: Part A gives roughly 67 seconds per question, which is tight for tracing and calculation questions. Part B gives around two minutes per question, so accuracy matters more than speed there.

Stage 2: Interview

The interview is held for shortlisted candidates and carries 100 marks.

How academic achievement marks are given

You need at least 50% in the interview if unreserved, and 40% if you are a PwBD candidate. Bring original documents that support everything entered online. If you are employed, an original No Objection Certificate (NOC) from your employer is required at the interview.

Final merit calculation

The final panel gives 50% weightage to the written test and 50% to the interview. The overall qualifying requirement in the advertisement is 60% aggregate for unreserved candidates and 50% for PwBD candidates, along with the stage-wise minimums above.

Illustrative example: if a candidate scores 72 out of 100 in the CBT and 78 out of 100 in the interview, the combined merit score is (72 + 78) divided by 2, which is 75. This example is only for understanding the method and is not an official figure.

If candidates tie, the advertisement applies these tie-breakers in order: written test marks, then marks in the essential qualification, then date of birth (older candidate placed higher). ISRO reserves the right to change interview and selection criteria for administrative reasons.

Time management and exam-day strategy

1. Start with your strongest subjects in Part A: Secure the easy conceptual questions first, then return to calculation-heavy ones.

2. Cap each tracing question: If a scheduling or subnetting problem passes two minutes, mark it and move on.

3. Use the elimination rule: Attempt a doubtful question only when you can remove at least one option.

4. Finish Part B completely: Spend the full time and answer every question.

5. Practise in the real format: Take timed mocks with the same part structure so the timing is automatic by test day.

You can build this habit with ISRO Scientist CS mock tests on Testkart, where the section-wise analysis shows accuracy and time per part. Check last cycle's benchmark on the ISRO Scientist CS cut-off page.

Older pages may still show earlier ISRO patterns, so follow the official advertisement on isro.gov.in.