Questions: Memory, Data Storage, and Variables

Question 1

After the following three lines execute, what is the value of x? x = 5 x = x + 3 x = x * 2

• A. 16
• B. 5
• C. 26
• D. 10

Answer: (A)

Assignment executes in order and replaces the current value each time. After x = 5, x holds 5. After x = x + 3, x holds 8 (5 + 3). After x = x * 2, x holds 16 (8 × 2). Option B (5) reflects the misconception that only the first assignment 'sticks.' Option D (10) comes from applying only the last operation to the original value (5 × 2). Each assignment overwrites the previous value — the variable holds exactly one value at any given moment.

Question 2

Which statement best describes what a variable is in a computer program?

• A. A named location in memory where a value can be stored and changed
• B. A permanent label attached to a specific value that travels with it
• C. A mathematical symbol representing an unknown, like in an algebra equation
• D. A formula that computes a result each time it is evaluated

Answer: (A)

A variable is a named memory slot — it has a fixed location but a changeable value. Option B inverts the relationship: the name stays fixed while the value changes. Option C reflects the algebra metaphor, where 'x' represents an unknown to solve for; in programming, x is a container you fill. Option D describes a function. The key property is mutability: the same name can hold different values at different points during execution.

Question 3

When you write `name = 'Alice'` and then `name = 'Bob'`, the program stores both values and you can access either one later.

• T. True
• F. False

Answer: False

Assignment replaces the current value at the memory location. After the second statement, 'Alice' is overwritten and gone — only 'Bob' remains under `name`. Variables hold one value at a time. The old value is not preserved anywhere unless you explicitly stored it in a separate variable first.

Question 4

The order in which assignment statements appear in a program can change the final value of a variable.

• T. True
• F. False

Answer: True

Since each assignment reads the current value and then overwrites it, sequence matters. `x = 5` followed by `x = x * 2` gives 10, but writing `x = x * 2` before `x = 5` would fail (x has no value yet) or produce a different result. Order of execution is fundamental to how programs accumulate state — this is why reading code line by line, in order, is the right mental model.

Question 5

A student writes `score = 0` at the start of a program, then later writes `score = 100`. They expect the program to remember that the score was once 0. What actually happens, and why does this matter?

Model answer: The memory location named `score` is overwritten with 100; the value 0 is gone permanently. Variables hold exactly one value at a time, and assignment always replaces whatever was there before. If the student needs both values, they must store them in separate variables (e.g., `initial_score = 0` and `score = 100`). This matters because forgetting that assignment is destructive leads to bugs where expected values silently disappear.

This is the core mutation model of variables: the name stays bound to the same location, but the contents of that location change. Every assignment operation is a write that clobbers whatever was stored before. Programmers who treat variables as accumulators of history — rather than single current values — misunderstand the memory model and produce incorrect programs.