B2.1 Programming fundamentals: notes and practice

What you need to know

Our summary of the topic in our own words, not the IB guide.

• Declare and assign variables of the common primitive types
• Choose an appropriate data type for a given value and explain why
• Distinguish local from global scope and predict which value a name refers to
• Trace a program by hand and record variable values at each step in a trace table
• Apply arithmetic, comparison and logical operators correctly, including operator precedence
• Convert between data types explicitly and explain when conversion loses information
• Extract a substring from a string by position
• Manipulate strings by concatenating, searching, replacing and changing case
• Split a string on a delimiter and rejoin parts
• Explain what an exception is and when a program should handle one
• Write code that catches an exception and recovers, rather than crashing
• Validate input so that bad data is rejected before it causes an error
• Distinguish syntax, runtime and logic errors and identify which one a described failure is
• Debug a program using tracing, test output and breakpoints, and explain the fix
• Design test cases including normal, boundary and invalid inputs

Learn it

• Join text with +

  Lesson with 2 exercises

• A variable holds one value; assigning again replaces it

  Lesson with 3 exercises

• Four basic types

  Lesson with 1 exercise

• Turn typed text into a number

  Lesson with 4 exercises

• Operators and precedence

  Lesson with 3 exercises

• Whole-number division and remainder

  Lesson with 3 exercises

• Keeping the fraction; when conversion loses information

  Lesson with 2 exercises

• Comparison operators

  Lesson with 2 exercises

• Remainder inside a condition

  Lesson with 2 exercises

• Comparing text

  Lesson with 2 exercises

• and, or, not

  Lesson with 3 exercises

• Every loop needs an update; find the infinite loop

  Lesson with 2 exercises

• Local and global scope

  Lesson with 5 exercises

• Length and one character by position

  Lesson with 4 exercises

• Substring by position

  Lesson with 3 exercises

• Search, replace, change case

  Lesson with 5 exercises

• Loop over the characters

  Lesson with 5 exercises

• Split a line into parts; join parts

  Lesson with 3 exercises

• Capstone: read record lines, split, report

  Lesson with 1 exercise

• Syntax, run-time and logic errors

  Lesson with 2 exercises

• Find a bug by tracing and printing

  Lesson with 3 exercises

• What an exception is

  Lesson with 1 exercise

• Catch and recover

  Lesson with 2 exercises

• Validate before use

  Lesson with 4 exercises

• Design test cases: normal, boundary, invalid

  Lesson with 2 exercises

Practice questions

Original questions written for the 2027 course, marked as you go. Easiest first.

• Add agesCoding · Warm-up
• Bike hire test dataWritten · Warm-up
• Closed signCoding · Warm-up
• Data lossWritten · Warm-up
• Data typesWritten · Warm-up
• Double itCoding · Warm-up
• Exception ageWritten · Warm-up
• First characterCoding · Warm-up
• First N charactersCoding · Warm-up
• Fizz checkCoding · Warm-up
• Minutes to hoursCoding · Warm-up
• Name tagCoding · Warm-up
• Repeat lineCoding · Warm-up
• Same wordCoding · Warm-up
• Snack orderCoding · Warm-up
• Ticket costCoding · Warm-up
• Trace: div modTrace table · Warm-up
• Trace: precedenceTrace table · Warm-up
• Trace: replace valueTrace table · Warm-up
• Trace: two variablesTrace table · Warm-up
• Check a nicknameCoding · Warm-up
• Which kind of errorWritten · Warm-up
• Bill share errorsWritten · Core
• Booking boundary bugWritten · Core
• Coin changeCoding · Core
• Count a letterCoding · Core
• Characters at even indexesCoding · Core
• Ask until it is a numberCoding · Core
• Last characterCoding · Core
• Leap year checkCoding · Core
• Fix the dry spell counterCoding · Core
• The longest wordCoding · Core
• Mark checkerCoding · Core
• Copies leftCoding · Core
• Trace table: finding freezing hoursTrace table · Core
• RectangleCoding · Core
• Remove first and lastCoding · Core
• Reverse the wordsCoding · Core
• Scope shadowWritten · Core
• Scores on one lineCoding · Core
• Split billCoding · Core
• Swap halvesCoding · Core
• Tidy a product codeCoding · Core
• Total priceCoding · Core
• Trace: case and replaceTrace table · Core
• Trace: case and replace (Java)Trace table · Core
• Trace: char atTrace table · Core
• Trace: char at (Java)Trace table · Core
• Trace: count in a wordTrace table · Core
• Trace: count in a word (Java)Trace table · Core
• Trace: find skipped valueTrace table · Core
• Trace: find skipped value (Java)Trace table · Core
• Trace: Java reverseTrace table · Core
• Trace: local scopeTrace table · Core
• Trace: local scope (Java)Trace table · Core
• Trace: param scopeTrace table · Core
• Trace: param scope (Java)Trace table · Core
• Type lineCoding · Core
• Before the @Coding · Core
• Is it an hour?Coding · Core
• Validate percentageWritten · Core
• Sports day reportCoding · Stretch

Exam tips for B2.1

• Trace tables are a common Paper 2 skill. Practise them until each row is automatic.
• Know the difference between syntax, runtime and logic errors, with an example of each.
• When designing tests, include normal, boundary and invalid inputs.