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Common exam pitfall
Students often treat SUBSTRING as 0-indexed or treat the third parameter as the end index instead of length.
A STRING is a sequence of characters. A CHAR stores one character. Storage width depends on encoding; neither declaration is a promise of one byte.
Routine | Example | Result |
|---|---|---|
LENGTH | LENGTH("River") | 5 |
SUBSTRING | SUBSTRING("River",2,3) | "ive" |
UCASE | UCASE("River") | "RIVER" |
LCASE | LCASE("RiVER") | "river" |
UCASE and LCASE work with strings as well as characters. This course and its runner use position 1 for the first character in SUBSTRING; check the convention stated in another system or question. The third argument is the number of characters, not the ending position.
Worked username
For first name Mira and surname Santos, SUBSTRING("Mira",1,1) gives M. Concatenate using &: M & Santos gives MSantos. LCASE converts the whole result to msantos. Converting only the first character would leave the surname's capitals unchanged.
Independent practice
Trace SUBSTRING("COMPUTER",3,4), then apply LCASE. The extracted string is MPUT and the lowercase result is mput. Now use different names in the username exercise.
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Exam-Style Check: Cambridge SUBSTRING Evaluation
• Multiple ChoiceUse this course’s 1-based string indexing. In Cambridge pseudocode, what string value is returned by the expression: SUBSTRING("ALGORITHM", 3, 4)?
Interactive exercises for Module 2 and beyond require an active plan.