Machine Input Output Questions Placement
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
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Not Identifying Pattern Early: Spend time upfront to understand the rule.
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Assuming Simple Sorting: Not all patterns are simple ascending/descending.
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Losing Track of Elements: In complex patterns, elements may move unpredictably.
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Ignoring Given Steps: Always verify your understanding with ALL given steps.
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Calculation Errors: In mathematical patterns, double-check arithmetic.
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Not Noticing Multi-Element Changes: Some steps may move multiple elements.
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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!