Loading...
Choose representations from the meaning of the data, then apply operations with explicit language rules. A value that looks numeric is not necessarily a quantity to calculate with.
What you'll be able to do
An integer represents whole-number values, a real/float approximates a wider set of numerical values, and a Boolean represents true or false. Characters, strings and date/time values have different operations. A telephone identifier should usually be a string: leading zeroes and punctuation matter, while arithmetic on it is meaningless.
Arrays and records group values; a user-defined record can combine fields with different types. A pointer or reference identifies a dynamically created object rather than containing every field of that object inline. Not every language exposes raw memory addresses, so distinguish the model from the syntax.
Assignment associates a value with a variable; later assignment can change that association. A named constant expresses a fixed value or policy, improving readability and making changes easier to audit. Python capitalisation is a convention, whereas some languages enforce constant declarations.
Use meaningful names that describe quantities and units. A constant named MAX_ATTEMPTS explains a limit better than an unexplained 3. A declaration can specify a type in some languages; Python names instead refer to typed objects. Do not claim all languages require identical declaration syntax.
Real division and integer division answer different questions. In Python 3, / produces a division result while // uses floor division; % gives a remainder and ** exponentiation. For non-negative integers, quotient and remainder satisfy dividend=quotient×divisor+remainder. Negative-operand rules should be checked for the language used.
Rounding selects a nearby representable value; truncation discards a fractional part towards zero. Python round has tie rules, so do not assume every language rounds a half upwards. Convert numeric text deliberately and check whether floating approximation is suitable for exact decimal quantities.
MAX_ATTEMPTS = 3
items = 17
boxes = items // 5
left_over = items % 5
print(boxes, left_over)Attempt the task before opening its worked response. Record each change of state, explain the rule used, and check the result against the original requirements. Code examples labelled Python 3 use that language’s conventions; pseudocode states its own assumptions.
Common mistakes to avoid
Key takeaways
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.