Unit 3: Flow chart and Alpha numeric coding

1. Flow Chart: Problems Based on Data Flow Diagrams

Flowcharts and Data Flow Diagrams (DFDs) are graphical representations used to illustrate a process, system, or computer algorithm. In analytical reasoning, these diagrams are used to test a student's ability to follow a logical sequence of instructions, make decisions based on conditions, and track the flow of data.

Key Symbols in Flowcharts

To solve flowchart problems, it is crucial to understand standard flowchart symbols:

• Oval / Pill: Terminal (Start/End). Indicates the beginning or end of a process.
• Parallelogram: Input/Output. Used for receiving data or displaying results.
• Rectangle: Process. Represents a mathematical computation, variable assignment, or data manipulation.
• Diamond: Decision. Represents a conditional statement (e.g., Is X > Y?). It always has two or more outgoing paths (usually True/Yes and False/No).
• Arrows: Flowlines. Indicate the direction of the data flow or logical sequence.

Strategies for Solving Flowchart Problems

1. Trace the Variables: Create a table to track the value of each variable at every step.
2. Follow the Logic Strictly: Do not assume anything outside the diagram. If a loop exists, follow it until the exit condition is met.
3. Identify the Exit Condition: In looping processes (diamonds that loop back to earlier rectangles), determine exactly what condition breaks the loop.

Example Problem Walkthrough

Diagram Logic:

1. START
2. Input
3. Set ,
4. Decision: Is ?
   • If YES -> Go to Step 7
   • If NO -> Go to Step 5
5. Process:
6. Process: -> Loop back to Step 4
7. Output
8. END

Output Result: 120 (This flowchart calculates the factorial of ).

2. Alpha Numeric Coding

Alpha numeric coding involves encrypting and decrypting data using letters, numbers, and symbols based on specific logical rules. Mastery of positional values of the English alphabet is mandatory.

Alphabet Positional Values

Memorizing the forward and backward positions of the alphabet is essential:

• Forward Order (A=1 ... Z=26):
  • Trick: EJOTY (E=5, J=10, O=15, T=20, Y=25)
• Backward Order (Z=1 ... A=26):
  • Trick: Reverse value = (e.g., Reverse of C(3) = ).

2.1 Coding and Decoding

Coding is the process of hiding the meaning of a message by applying a specific logic. Decoding is the process of revealing it.

Types of Coding:

1. Letter Coding: Letters are replaced by other letters.
   • Example: If "CAT" is coded as "ECV" (Pattern: +2 for each letter), then "DOG" becomes "FQI".
2. Number/Symbol Coding: Letters are assigned specific numbers or symbols.
   • Example: If "BAT" = 23 (B=2, A=1, T=20; ), then "CAT" = 24 ().
3. Substitution Coding: Specific words are substituted with other words.
   • Example: If 'white' is called 'blue', 'blue' is called 'red', and 'red' is called 'yellow', what is the color of human blood?
   • Answer: The actual color is red. In this code, 'red' is called 'yellow'. Therefore, the answer is 'yellow'.

2.2 Number Series

A sequential arrangement of numbers following a certain mathematical pattern.

Common Patterns:

1. Arithmetic Series: Constant addition or subtraction. (e.g., 5, 8, 11, 14, 17... Pattern: +3)
2. Geometric Series: Constant multiplication or division. (e.g., 2, 6, 18, 54... Pattern: x3)
3. Squares and Cubes Series: Based on or . (e.g., 1, 4, 9, 16, 25... Pattern: )
4. Prime Number Series: Sequence of prime numbers. (e.g., 2, 3, 5, 7, 11, 13...)
5. Double Difference Series: The differences between consecutive numbers form a series themselves.
   • Example: 4, 11, 24, 45, 76
   • Differences: 7, 13, 21, 31
   • Differences of differences: 6, 8, 10 (Arithmetic series)

Strategy: Always check the difference between adjacent numbers first. If the difference increases rapidly, check for multiplication or squares/cubes.

2.3 Alphabet Series

Similar to number series, but involves sequences of letters.

Problem Types:

1. Single Letter Series:
   • Example: A, C, F, J, O, ?
   • Logic: A(+2)=C, C(+3)=F, F(+4)=J, J(+5)=O, O(+6)=U. Answer: U.
2. Multi-Letter Series: Look at the relationship of the first letters together, second letters together, etc.
   • Example: DEF, HIJ, MNO, ?
   • Logic: First letters: D(+4)=H, H(+5)=M, M(+6)=S. The series continues similarly. Answer: STU.
3. Continuous Pattern Series: A sequence of small letters with blanks.
   • Example: a b d a b a n a a d
   • Strategy: Count total spaces and letters. Divide into equal groups (e.g., groups of 3 or 4) and look for a repeating pattern.

2.4 Alphanumeric Series

These series combine letters, numbers, and sometimes symbols.

Common Formats:

1. Missing Term in a Sequence:

   • Example: Z1A, X2D, V6G, T21J, ?
   • Logic:
     • First letter: Z(-2)=X, X(-2)=V, V(-2)=T, T(-2)=R.
     • Number: ; ; ; .
     • Third letter: A(+3)=D, D(+3)=G, G(+3)=J, J(+3)=M.
   • Answer: R88M.

2. Sequence Analysis (Condition-based):

   • A string of elements is given: W % 9 3 G 6 & H # 4 B @ 7
   • Question: How many numbers are immediately preceded by a symbol and immediately followed by a letter?
   • Logic: Look for the pattern: [Symbol] [Number] [Letter].
   • Checking: % 9 3 (No, letter doesn't follow). & doesn't precede a number. # 4 B (Yes: Symbol '#', Number '4', Letter 'B').
   • Answer: 1.

2.5 Alphabet Test

Tests based on the arrangement of letters in the English dictionary or logical word formations.

Key Problem Types:

1. Dictionary Order: Arranging given words exactly as they would appear in a dictionary.

   • Example: Arrange: 1. Epitaxy 2. Episode 3. Epigene 4. Epitome 5. Epilogue.
   • Logic: Compare letter by letter. All start with "Epi". The 4th letters are: t, s, g, t, l. Alphabetical order of 4th letters: g, l, s, t, t.
   • Order: Epigene (3), Epilogue (5), Episode (2), Epitaxy (1), Epitome (4).
   • Sequence: 3, 5, 2, 1, 4.

2. Letter-Word Formation: Forming a meaningful word from jumbled letters or specified positions of letters in a word.

   • Example: If a meaningful word can be formed using the 1st, 3rd, 5th, and 8th letters of the word 'REASONING', what is the last letter of the word?
   • Letters: R (1st), A (3rd), O (5th), N (8th).
   • Possible Word: ROAN (a color of a horse). Last letter is N.

3. Position within a Word: Finding letters in a word that have the same number of letters between them as in the English alphabet.

   • Example: How many pairs of letters in the word "NURSING" have as many letters between them in the word as in the alphabet?
   • Analysis:
     • Forward: N-U, N-R, N-S, N-I, N-N, N-G... R-S (Yes, R and S are adjacent in the alphabet and the word).
     • Backward: G-N, I-N (Yes, J,K,L,M - 4 letters between I and N in alphabet, but only 3 in word - no), G-I (Yes, H is between them in alphabet, N is between them in word. 1 letter space).
   • Pairs: R-S, G-I.