11. Programming

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Dotted terms are defined in the glossary.

• Hello — INPUT, OUTPUT & arithmetic

  Read a name and an age, then output a sentence built from several values.

  O LevelASPseudocodeBasics & data types §2.4, §5.1
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• The five basic data types

  INTEGER, REAL, CHAR, STRING and BOOLEAN — how each is declared, written and output.

  O LevelASPseudocodeBasics & data types §2.1–2.2
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• Constants & expressions

  CONSTANT for values that never change; brackets and ROUND to control the result.

  O LevelASPseudocodeBasics & data types §2.5, §5.2
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• DIV and MOD — quotient and remainder

  Convert minutes to hours and minutes, then give change using the fewest coins.

  O LevelASPseudocodeBasics & data types §5.2
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• Relational & logic operators

  Every comparison gives TRUE or FALSE; AND, OR and NOT combine them.

  O LevelASPseudocodeBasics & data types §5.3–5.4
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• Converting between types

  NUM_TO_STR, STR_TO_NUM, ASC and CHR — the library routines that move between numbers, strings and characters.

  O LevelASPseudocodeBasics & data types 2210 §8.1 library routines
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• The DATE type (9618)

  Date literals, DAY/MONTH/YEAR and comparing dates — used to work out an age.

  ASA2PseudocodeBasics & data types §2.1–2.2
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• IF … THEN … ELSE

  Pass or fail from a single input.

  O LevelASPseudocodeSelection §6.1
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• Nested IF — grade boundaries

  There is no ELSEIF in Cambridge pseudocode: nest the IFs and close every ENDIF.

  O LevelASPseudocodeSelection §6.1
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• CASE OF — a menu

  One value, many outcomes; OTHERWISE catches everything else.

  O LevelASPseudocodeSelection §6.2
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• CASE with ranges and lists

  Ranges like 5 TO 17 and lists like "Sat", "Sun" on one line each.

  O LevelASPseudocodeSelection §6.2
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• Complex conditions — leap year

  AND, OR and NOT with brackets to make the order of evaluation explicit.

  O LevelASPseudocodeSelection §5.4
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• FOR loop & totalling

  A count-controlled loop that accumulates a running total.

  O LevelASPseudocodeIteration §7.1
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• FOR with STEP

  Count down with a negative step, and count in twos.

  O LevelASPseudocodeIteration §7.1
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• WHILE with a sentinel — totalling & counting

  Read numbers until -1; INPUT once before the loop and again at the end of the body.

  O LevelASPseudocodeIteration §7.3 · 2210 WHILE … DO
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• REPEAT … UNTIL — password with 3 attempts

  A post-condition loop runs at least once; the condition is checked at the end.

  O LevelASPseudocodeIteration §7.2
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• Nested FOR loops — times-table grid

  The inner loop runs completely for every pass of the outer loop.

  O LevelASPseudocodeIteration §7.1
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• The same job with FOR, WHILE and REPEAT

  Count-controlled, pre-condition and post-condition loops side by side.

  O LevelASPseudocodeIteration §7.1–7.3
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• 9618 string functions (§5.5)

  LENGTH, MID, RIGHT, LCASE/UCASE on a CHAR and & for joining — the functions the exam always provides.

  ASA2PseudocodeString handling §5.5
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• Reverse a string

  Walk the string backwards with STEP -1 and build a new one.

  O LevelASPseudocodeString handling §5.5, §7.1
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• Palindrome check

  Lower-case the word, reverse it, compare.

  O LevelASPseudocodeString handling §5.5
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• Count the vowels

  Take one character at a time and test it against a list of values.

  O LevelASPseudocodeString handling §5.5
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• Initials from a full name

  Find each space and take the character after it.

  O LevelASPseudocodeString handling §5.5
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• Word count & longest word

  Split a sentence on spaces without any split function — track the current word as you go.

  O LevelASPseudocodeString handling §5.5
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• Letters, digits or other?

  Compare characters with ranges like 'A' to 'Z' — the basis of format checks.

  O LevelASPseudocodeString handling §5.3
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• Frequency count of 600 dice rolls

  The dice value is used directly as the array index — no IF needed.

  O LevelASPseudocodeArrays §5.6
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• Procedures with parameters

  A procedure that draws a line, called by another procedure that draws a triangle.

  O LevelASPseudocodeProcedures & functions §8.1
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• Functions that RETURN a value

  Functions are used inside expressions — never with CALL.

  O LevelASPseudocodeProcedures & functions §8.2
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• BYREF vs BYVAL

  BYVAL works on a copy; BYREF changes the caller's variable. Watch X before and after.

  ASA2PseudocodeProcedures & functions §8.3
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• Local vs global variables

  A DECLARE inside a procedure makes a new local variable; without one, the global is used.

  O LevelASPseudocodeProcedures & functions 2210 §8.1 / 9618 §11.3
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• Passing an array to a procedure and a function

  Fill an array BYREF, then total it with a function.

  ASA2PseudocodeProcedures & functions §8.1–8.3
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• Stepwise refinement — a bank menu built from modules

  The main program only shows the menu and CALLs procedures; each module does one job (a structure chart in code).

  ASPseudocodeProcedures & functions §8.1 · 9618 §9.1
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• AS Paper 2 — library loans

  An array of records, a search function, procedures for borrowing and reporting, all driven by a menu.

  ASPseudocodeExam-style tasks §4.2, §8
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• Hello — input(), print() and f-strings

  Read a name and an age, convert the age with int(), and print a sentence. The Python twin of the first pseudocode example.

  O LevelASPythonBasics & data types §2.4, §5.1 ↔ Python
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• Data types: int, float, str, bool

  Python works out the type from the value — type() shows it. Compare with DECLARE in pseudocode.

  O LevelASPythonBasics & data types §2.1–2.2 ↔ Python
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• Constants (by convention) and rounding

  Python has no CONSTANT keyword — UPPER_CASE names signal a value that must not change. round() controls decimal places.

  O LevelASPythonBasics & data types §2.5 ↔ Python
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• // and % — quotient and remainder

  Minutes to hours and minutes, and change with the fewest coins. // is DIV, % is MOD.

  O LevelASPythonBasics & data types §5.2 ↔ Python
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• Converting between str and numbers

  input() always gives a str. int() and float() convert it; str() goes the other way. The #1 cause of TypeError.

  O LevelASPythonBasics & data types §5.5 NUM_TO_STR ↔ Python
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• if / elif / else — grade boundaries

  elif replaces the nested IF … ELSE … ENDIF of pseudocode. Conditions are checked in order; the first true one wins.

  O LevelASPythonSelection §6.1 ↔ Python
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• match / case — the CASE statement

  Python 3.10+ has match, the closest thing to CASE OF … OTHERWISE. Ranges are written as guards.

  O LevelASPythonSelection §6.2 ↔ Python
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• Boolean conditions — and, or, not

  Leap years and a login check. Note the lower-case and / or / not, and == for comparison.

  O LevelASPythonSelection §5.3 ↔ Python
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• for … in range() — counted loops

  range(1, 6) is FOR i ← 1 TO 5. range(10, 0, -2) counts down. The end value is not included!

  O LevelASPythonIteration §7.1 ↔ Python
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• while — condition-controlled loop

  WHILE … ENDWHILE. Python has no REPEAT … UNTIL: write while True with a break, or test the condition first.

  O LevelASPythonIteration §7.2–7.3 ↔ Python
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• Nested loops — times table

  One loop inside another; end="\t" keeps each row on one line.

  O LevelASPythonIteration §7.1 ↔ Python
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• String handling — len, slicing, upper, lower

  Python strings are indexed from 0. s[i], s[a:b], len(), .upper(), .lower() replace LENGTH, SUBSTRING, UCASE, LCASE.

  O LevelASPythonString handling §5.5 ↔ Python
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• Reverse a string and test a palindrome

  Loop version (exam-style) and the slice trick s[::-1].

  O LevelASPythonString handling §5.5 ↔ Python
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• Count vowels and words

  Character-by-character loop with in, then split() to count words.

  O LevelASPythonString handling §5.5 ↔ Python
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• Caesar cipher with ord() and chr()

  Shift each letter by a key, wrapping round the alphabet with %. Non-letters are left alone.

  O LevelASPythonString handling §5.5 ↔ Python
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• Functions and procedures — def and return

  A procedure is a def with no return; a function returns a value. Parameters are passed by value for numbers/strings.

  O LevelASPythonProcedures & functions §8.1–8.2 ↔ Python
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• BYVAL vs BYREF in Python

  Numbers and strings behave like BYVAL; a list passed to a function behaves like BYREF — changes inside are seen outside. To return two values, return a tuple.

  ASPythonProcedures & functions §8.3 ↔ Python
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• Local and global scope

  A variable assigned inside a function is local. global makes a function change a module-level variable — usually better to return a value instead.

  ASPythonProcedures & functions §8.4 ↔ Python
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• Logic gates and a truth table

  Build AND, OR, XOR, NAND from Boolean operators and print the truth table of an expression.

  O LevelASPythonTheory in code 2210 §10 / 9618 §3
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• Largest of three numbers

  Nested decisions: the chart shows why the second comparison depends on the first.

  O LevelASSelection 2210 §7
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• Grade from a mark (CASE)

  A CASE statement becomes a chain of decisions, each branch to the right.

  O LevelASSelection 2210 §8.1
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• Count 1 to 10 (FOR)

  The FOR loop drawn the Cambridge way: set counter, test, body, add one, loop back.

  O LevelASLoops 2210 §8.1
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• Keep doubling (WHILE)

  Pre-condition loop: the test is at the top, so the body may never run.

  O LevelASLoops 2210 §8.1
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• Guess the number (REPEAT)

  Post-condition loop: the decision sits at the bottom, so the body runs at least once.

  O LevelASLoops 2210 §8.1
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• Nested loops (grid)

  A loop inside a loop: the inner arrow-back sits inside the outer one.

  O LevelASLoops 2210 §8.1
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• Total and average of N numbers

  Totalling and counting together, then a division after the loop — the classic 2210 Q.

  O LevelASTotalling, counting, max / min 2210 §7
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• Highest and lowest of 10 marks

  Set max low and min high, then one decision each inside the loop.

  O LevelASTotalling, counting, max / min 2210 §7
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• Range check with a rejection loop

  Keep asking until the value is between 1 and 100 — the validation flowchart every paper wants.

  O LevelASValidation & rejection loops 2210 §7
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• Fill an array of 5 names

  The loop counter doubles as the array index.

  O LevelASArrays 2210 §8.2
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• Linear search

  Search an array for a value with a found flag — 2210 §7's standard method.

  O LevelASArrays 2210 §7
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• One pass of a bubble sort

  Compare neighbours and swap: the decision inside the loop with three process boxes.

  O LevelASArrays 2210 §7
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• Calling a procedure

  The main chart uses the subroutine symbol; the procedure gets its own chart tab.

  O LevelASSubroutines 2210 §8.1
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• A function with RETURN

  A function's chart ends with a RETURN terminator instead of Stop.

  ASSubroutines 9618 §11.3
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• Library system

  Top module with three sub-modules, parameters in and out, and an iteration mark on the loan loop.

  ASStructure charts (9618 §12.2) 9618 §12.2
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• Quiz program

  Selection and iteration marks: a question loop with a check inside it.

  ASStructure charts (9618 §12.2) 9618 §12.2
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• Payroll

  A wider chart: four modules at the second level, two of them with children.

  ASStructure charts (9618 §12.2) 9618 §12.2
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• Turnstile

  Two states, two events — the textbook state machine, with its transition table.

  ASState-transition diagrams (9618 §12.2) 9618 §12.2
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• Traffic light

  A cycle of states driven by a timer event.

  ASState-transition diagrams (9618 §12.2) 9618 §12.2
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• Vending machine

  States for money inserted; events for coins, choose and cancel; actions on some arrows.

  ASState-transition diagrams (9618 §12.2) 9618 §12.2
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• Login attempts

  A machine that locks the account after three wrong passwords.

  ASState-transition diagrams (9618 §12.2) 9618 §12.2
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