Machine Input-Output Questions for Placement 2026 (with Solutions)

Last Updated: March 2026

Introduction to Machine Input-Output

Machine Input-Output is an advanced reasoning topic where a given input undergoes a series of operations by a "machine" to produce step-by-step outputs. Unlike basic Input-Output, machine input-output problems involve more complex patterns like word-number manipulation, mathematical operations, shifting based on specific rules, and multi-step transformations. This topic is commonly asked in TCS NQT, Infosys, and other premium company placement exams.

Why This Topic is Important

Machine Input-Output questions assess:

Complex pattern recognition
Multi-step logical tracking
Ability to decode machine operations
Understanding of transformation rules
Speed and accuracy under pressure

Companies That Ask Machine Input-Output Questions

Company	Frequency	Difficulty Level
TCS NQT	High	Moderate to High
Infosys	Moderate	Moderate
Wipro	Moderate	Moderate
Cognizant	Low	High
Accenture	Low	Moderate
Capgemini	Low	High
Tech Mahindra	Moderate	Moderate

KEY FORMULAS / CONCEPTS

╔══════════════════════════════════════════════════════════════════╗
║            MACHINE INPUT-OUTPUT PATTERN TYPES                    ║
╠══════════════════════════════════════════════════════════════════╣
║                                                                  ║
║  TYPE 1: WORD-NUMBER ARRANGEMENT                                 ║
║  ────────────────────────────────────────────────────────────   ║
║  - Words arranged alphabetically/anti-alphabetically            ║
║  - Numbers arranged ascending/descending                        ║
║  - Alternating word-number arrangement                          ║
║  - Vowels first, then consonants                                ║
║  - Prime numbers first, then composite                          ║
║                                                                  ║
║  TYPE 2: MATHEMATICAL OPERATIONS                                 ║
║  ────────────────────────────────────────────────────────────   ║
║  - Sum of digits placed at ends                                 ║
║  - Product of first and last numbers                            ║
║  - Difference between adjacent elements                         ║
║  - Squares or cubes placed in specific positions                ║
║                                                                  ║
║  TYPE 3: SHIFTING PATTERNS                                       ║
║  ────────────────────────────────────────────────────────────   ║
║  - Fixed position swapping                                      ║
║  - Circular rotation (left/right)                               ║
║  - First to last, last to first                                 ║
║  - Middle element to ends                                       ║
║                                                                  ║
║  TYPE 4: LOGICAL OPERATIONS                                      ║
║  ────────────────────────────────────────────────────────────   ║
║  - Largest word/number moved to specific position               ║
║  - Smallest word/number moved to specific position              ║
║  - Elements rearranged based on length/value                    ║
║                                                                  ║
║  ANALYSIS APPROACH                                               ║
║  ────────────────────────────────────────────────────────────   ║
║  Step 1: Compare Input with Step 1                              ║
║  Step 2: Identify the transformation rule                       ║
║  Step 3: Verify rule with subsequent steps                      ║
║  Step 4: Predict final arrangement                              ║
║  Step 5: Answer specific questions                              ║
║                                                                  ║
╚══════════════════════════════════════════════════════════════════╝

30 Practice Questions with Step-by-Step Solutions

Set 1: Word Arrangement Pattern

Input: money power corrupts people absolutely

Step 1: absolutely money power corrupts people Step 2: absolutely corrupts money power people Step 3: absolutely corrupts money people power

Q1: What is the pattern? Answer: Words arranged in alphabetical order, one word fixed per step from the left.

Q2: How many steps needed for complete arrangement? Answer: 3 steps for 5 words.

Q3: Which word is at the last position in Step 2? Answer: people

Set 2: Number Arrangement Pattern

Input: 45 23 67 12 89 34

Step 1: 12 45 23 67 89 34 Step 2: 12 23 45 67 89 34 Step 3: 12 23 34 45 67 89

Q4: Identify the machine operation. Answer: Numbers arranged in ascending order, smallest number moved to its correct position each step.

Q5: What is the position of '67' in Step 2? Answer: 4th position

Q6: How many steps for complete arrangement? Answer: 3 steps

Set 3: Alternating Pattern

Input: 5 apple 3 banana 7 cherry 2 date

Step 1: 2 5 apple 3 banana 7 cherry date Step 2: 2 apple 5 3 banana 7 cherry date Step 3: 2 apple 3 5 banana 7 cherry date Step 4: 2 apple 3 banana 5 7 cherry date Step 5: 2 apple 3 banana 5 cherry 7 date

Pattern: Numbers in ascending order at odd positions, words alphabetically at even positions.

Q7: How many total steps? Answer: 5 steps

Q8: What is at position 4 in Step 3? Answer: banana

Set 4: Mathematical Operation Pattern

Input: 12 5 8 3 9 4

Step 1: 60 12 5 8 3 9 (60 = 12×5, product of first two placed at front, last element dropped) Step 2: 60 40 12 5 8 3 (40 = 5×8) Step 3: 60 40 24 12 5 8 (24 = 3×8... wait)

Clear pattern: Product of consecutive pairs placed at beginning:

Input: 12 5 8 3

Step 1: 60 8 3 12 5 (60=12×5, elements shift right) Step 2: 60 24 12 5 8 (24=8×3)

Q9: What operation is the machine performing? Answer: Product of consecutive pairs from input, results placed at beginning with shifting.

Set 5: Complex Word-Number

Input: tiger 45 lion 32 elephant 67 deer 23

Step 1: 23 tiger 45 lion 32 elephant 67 deer Step 2: 23 deer tiger 45 lion 32 elephant 67 Step 3: 23 deer 32 tiger 45 lion elephant 67 Step 4: 23 deer 32 elephant tiger 45 lion 67 Step 5: 23 deer 32 elephant 45 tiger lion 67 Step 6: 23 deer 32 elephant 45 lion tiger 67 Step 7: 23 deer 32 elephant 45 lion 67 tiger

Pattern: Alternating arrangement: smallest number, then alphabetically first word, then next smallest number, etc.

Q10: How many steps for complete arrangement? Answer: 7 steps

Q11: What is the position of 'tiger' in Step 4? Answer: 4th position

Set 6: Descending Order Pattern

Input: 23 56 12 89 45 67 34

Step 1: 89 23 56 12 45 67 34 Step 2: 89 67 23 56 12 45 34 Step 3: 89 67 56 23 12 45 34 Step 4: 89 67 56 45 23 12 34 Step 5: 89 67 56 45 34 23 12

Pattern: Descending order, largest number placed at correct position each step.

Q12: How many steps? Answer: 5 steps

Q13: Which number is at position 3 in Step 3? Answer: 56

Set 7: Vowel-Consonant Pattern

Input: zebra apple mango orange banana

Step 1: apple zebra mango orange banana Step 2: apple orange zebra mango banana Step 3: apple orange banana zebra mango

Pattern: Words starting with vowels first (alphabetically), then consonants.

Q14: What is the final arrangement? Answer: apple orange banana zebra mango

Q15: How many steps? Answer: 3 steps

Set 8: Multi-Operation Pattern

Input: 12 8 5 9 3 7

Step 1: 3 12 8 5 9 7 Step 2: 3 5 12 8 9 7 Step 3: 3 5 7 12 8 9 Step 4: 3 5 7 8 12 9 Step 5: 3 5 7 8 9 12

Pattern: Ascending order arrangement.

Q16: What is the position of '8' in Step 3? Answer: 4th position

Set 9: Reverse Alphabetical Pattern

Input: cat dog elephant rat tiger lion

Step 1: tiger cat dog elephant rat lion Step 2: tiger rat cat dog elephant lion Step 3: tiger rat lion cat dog elephant Step 4: tiger rat lion elephant cat dog Step 5: tiger rat lion elephant dog cat

Pattern: Reverse alphabetical (Z to A) arrangement.

Q17: Which word is at position 2 in Step 3? Answer: rat

Q18: How many steps for complete arrangement? Answer: 5 steps

Set 10: Prime-Composite Separation

Input: 5 12 7 18 11 24 13 9

Step 1: 5 7 11 13 12 18 24 9 Step 2: 5 7 11 13 9 12 18 24

Pattern: Prime numbers first (ascending), then composite numbers (ascending).

Q19: What is the final arrangement? Answer: 5 7 11 13 9 12 18 24

Q20: Which number is at position 6 in Step 1? Answer: 18

Questions 21-30: Mixed Practice

Q21: In an arrangement where words are arranged by length (shortest first), arrange: "the quick brown fox jumps" Answer: the fox quick brown jumps (2, 3, 5, 5, 5... actually: the=3, fox=3, quick=5, brown=5, jumps=5) Final: the fox brown quick jumps (alphabetical for same length)

Q22: Input: 45 32 67 23 89 12. If arranged in ascending order, how many steps? Answer: 5 steps for 6 numbers

Q23: Input: zebra apple mango. Reverse alphabetical order - how many steps? Answer: 2 steps: zebra mango apple

Q24: In a word arrangement, if Step 3 is "apple banana cherry date fig" and pattern is alphabetical, what was the input? Answer: Could be any order; one possibility: fig apple cherry banana date

Q25: Input: 8 3 9 2 7 4. If even numbers are placed first in ascending order, then odd numbers: Answer: 2 4 8 3 7 9

Q26: Arrange by last letter alphabetical: cat dog elephant tiger Last letters: t, g, t, r Answer: dog, tiger, cat, elephant (cat before elephant alphabetically)

Q27: Input with numbers and words: 5 tiger 3 lion 7 deer. Arrange numbers ascending, words alphabetical: Answer: 3 5 7 deer lion tiger

Q28: Circular left shift pattern (first goes to last): Input: A B C D E Step 1: B C D E A After how many steps original arrangement? Answer: 5 steps (equal to number of elements)

Q29: If input is "12 34 56 78 90" and operation is "sum of first and last placed at beginning": Step 1: 102 12 34 56 78 Step 2: 180 102 12 34 56 Pattern: Sum of current first and last placed at beginning

Q30: Complex pattern detection: Input: 4 2 8 6 10 Step 1: 2 4 8 6 10 Step 2: 2 4 6 8 10 What is the pattern? Answer: Ascending order arrangement

SHORTCUTS & TRICKS

Trick 1: Identify Fixed Elements First

Look for elements that reach their final position and never move again.

Trick 2: Pattern Recognition Categories

Most patterns fall into:

Ascending/Descending
Vowel-Consonant separation
Prime-Composite separation
Odd-Even separation
Word length arrangement
Alphabetical/Anti-alphabetical

Trick 3: Count Steps Formula

For simple sorting: Maximum steps = Number of elements - 1

Trick 4: Track One Element

Follow a single element through all steps to understand the transformation.

Trick 5: Work Backwards

Sometimes easier to determine final arrangement, then trace back.

Trick 6: Look for Pairs

In mathematical operations, look for how pairs of elements combine.

Trick 7: Write Minimal Information

Don't rewrite entire arrangement every time - track only changes.

Common Mistakes to Avoid

Not Identifying Pattern Early: Spend time upfront to understand the rule.
Assuming Simple Sorting: Not all patterns are simple ascending/descending.
Losing Track of Elements: In complex patterns, elements may move unpredictably.
Ignoring Given Steps: Always verify your understanding with ALL given steps.
Calculation Errors: In mathematical patterns, double-check arithmetic.
Not Noticing Multi-Element Changes: Some steps may move multiple elements.
Time Mismanagement: Don't spend too long on one pattern - move on if stuck.

5 Frequently Asked Questions

Q1: How do I quickly identify complex patterns? A: Look for: (1) Which elements moved? (2) Where did they move? (3) What's the selection criterion?

Q2: What if I can't find the pattern? A: Try common patterns: ascending, descending, vowels-first, shortest-first, prime-first.

Q3: How many steps should I write out? A: Write until the pattern is clear, then jump to answer. Don't write unnecessary steps.

Q4: Are Machine Input-Output questions difficult? A: They can be tricky initially, but with practice, patterns become recognizable.

Q5: How much time should I allocate? A: 90-120 seconds for pattern identification + 15-30 seconds per question.

Master these 30 questions to excel at Machine Input-Output in your placement exams!

Machine Input Output Questions Placement