Week 1 — variables & representation

Quiz 2 scope: Weeks 1–8 per IITM May 2026 foundation courses. Source baseline: IITM BS admissions important-dates calendar · May 2026 cycle. Times on assessments are operational conventions — verify hall ticket.

Week map

Classify → Represent → Execute → Trap-check

• Recognize: Ask: What does a diamond represent in a flowchart?
• Procedure: Follow arrows from Start. At diamond, one branch taken. Update variables in rectangles before next decision.
• Variations / traps: Watch for: Skipping decision branch label (Y/N).

Formula chain (compressed)

state variables → datatype → assignment updates → flowchart ↔ trace.

1. State — named variables hold values — trace step by step
2. Assignment — x ← expression — RHS evaluated first
3. Iterator — loop counter / index — repeated steps
4. Datatype — int, float, str, bool — legal operations
5. Flowchart — boxes + arrows — algorithm before code

Deep study

Computational Thinking · Week 1 — Variables and state

Week map

Representation notation

• Variable → name bound to a value that may change → count, total, name.
• State → all current variable values at one instant → snapshot table one row per step.
• Iterator → variable stepping through a sequence or count → i from 0 to n-1.
• Datatype → kind of value → determines legal operations → number vs string vs list.

Flowchart symbols

Choosing a representation

1. Single vs collection? One score → number; list of scores → list.
2. Fraction allowed? Integer count vs float average.
3. Text vs number? ID as string even if digits; phone codes not for arithmetic.

State snapshot tracing

Pattern families

Easy — Read flowchart step

• Follow arrows; update rectangles; branch at diamond once.
• Identify start/end and missing arrow bugs in diagrams.
• Match parallelogram to Read/Print in trace.

Medium — Choose datatype and names

• From word problem, list variables and types.
• Distinguish index (position) vs value at index.
• Flowchart with two variables swapping — track both columns.

Hard — Full state table

• Multi-step with decision: duplicate row only along taken branch.
• Iterator introduced mid-flow: when does i increment?
• Detect unreachable rectangle (no arrow in).

Worked mini-examples

Traps

• Skipping decision branch label — both paths mentally.
• Same name for two concepts (total for both count and sum).
• Using value before rectangle that assigns it.
• Iterator confused with stored data value (i vs item[i]).
• Flowchart arrow bypassing update rectangle.

Diagnostic (try yourself)

1. Start p=5, q=3. Execute p ← p + q then q ← p - q. What are final p and q?
2. A flowchart diamond asks x < 0. If x = 0, which branch (Y/N) is taken for “less than zero”?
3. You need to store a student’s 8 weekly quiz percentages. One variable or a collection? Which datatype class?
4. Trace c=1, d=4, then c ← d, d ← c. What are c and d? (Watch order.)
5. In a state table, why duplicate rows only on the taken branch after a decision?

ChatGPT prep archive

• Chatty reference archive

Archived import for extra depth — complements the notes above, not official IITM material.

Core concepts

• Variable names a value that can change; iterator often counts or walks a collection.
• Datatypes: number, string, boolean, list—operations depend on type.
• Flowchart: start/end ovals, process boxes, decision diamonds, arrows show order.
• State snapshot: all variable values at one step.

Notation & vocabulary

Pattern families

Easy — Read flowchart step

Medium — Choose representation

Hard — State table trace

Drill these on the pattern atlas — filter to week 1.

Traps

• Skipping decision branch label (Y/N).
• Same variable name for different concepts.
• Flowchart arrow bypassing a required update.
• Confusing iterator index with value stored.

Retrieval prompts

1. What does a diamond represent in a flowchart?
2. What is a state snapshot?
3. When represent data as list vs single variable?

Practice loop

1. Read Deep study (if present) or core concepts once.
2. Recite the formula chain without looking.
3. Open one easy pattern on the interactive atlas for week 1.
4. Attempt without solutions; mark studied after an honest try.
5. Say one trap aloud before closing the tab.

Related

• Full weeks 1–8 prep guide
• Pattern atlas note
• Formula chain desk