Binary tree traversal practice for AQA A Level Computer Science (7517): twenty different worksheets on pre-order, in-order and post-order traversal, each with a complete answer key. Every worksheet is built on a different binary tree, and no two trees in the pack have the same shape. You can set one sheet in class, a second for homework and a third for a resit without ever setting the same questions twice, and without drawing new trees yourself at eleven o’clock at night. WHAT YOU GET 20 worksheets, 3 pages each, numbered 01 to 20 20 matching answer keys A contents table listing the number of nodes, the mark total and the traversal shown in question 3 for every sheet, so you can pick a seven-node tree for a ten-minute starter or a twelve-node one for a full period WHAT IS ON EVERY SHEET Question 1 asks for all three traversals of the same tree, which is the point: pre-order, in-order and post-order only make sense against each other. Question 2 is answered from a table of nodes rather than from the diagram - Index, Left, Data, Right, with -1 for a missing child - and asks for a named child, the leaves and the depth. Question 3 shows a recursive subroutine and asks which traversal it performs, what it is used for, what stops the recursion, and what the same subroutine would output if it were called on a subtree. Mark totals are printed at the top of each sheet and beside every question. Sheets run from 17 to 20 marks, on trees of seven to twelve nodes.

Searching algorithms practice for AQA A Level Computer Science (7517): twenty different worksheets on linear search, binary search and binary tree search, each with a complete answer key. Every sheet runs all three algorithms on the same values, looking for the same target: the unsorted list, the same list sorted, and the binary search tree built from it. A student finishes the sheet having counted, say, twelve comparisons against four and five - and question 4 then asks them to explain the gap they have just measured, rather than to recite O(n) and O(log n) from memory. WHAT YOU GET 20 worksheets, 4 pages each, numbered 01 to 20 20 matching answer keys A contents table giving the number of values, the mark total and the comparison counts of every sheet, so you can set one where the contrast is stark or one where it is narrower WHAT IS ON EVERY SHEET Question 1 traces a linear search of an unsorted list and asks for the number of comparisons. Question 2 traces a binary search of the same values sorted, against the pseudocode printed on the sheet, in a table with Bottom, Top, Midpoint and the value there. Question 3 traces a binary tree search of the same values. Question 4 asks for the time complexity of all three, for an explanation of the gap between the first two counts, and for the largest number of comparisons a binary search could need on a list of several thousand items. The first row of every trace table is completed, so there is no doubt about where a trace begins. Sheets run from 19 to 20 marks. THE MIDPOINT RULE IS PRINTED ON THE SHEET On an even number of items there is no middle item, and a trace question that does not say which way to round has two correct answers. Every worksheet states the rule in its conventions and again in the pseudocode: Midpoint is (Bottom + Top) DIV 2, integer division, rounded down. Whatever your department teaches, the trace the sheet asks for is the one determined by what the student is looking at. WRITTEN FOR AQA The specification asks students to “know and be able to trace and analyse the complexity of the linear search algorithm”, and the same for binary search and binary tree search - AQA 7517, section 4.3.4, printed in the header of every page. Both verbs are on the sheet: three traces, then the complexity of each with a reason, in the specification’s own terms. The pseudocode follows AQA’s own written conventions: DIV for integer division, LEN for the length of an array, arrays indexed from 0, and the not- equal and less-than-or-equal symbols as AQA writes them. FORMAT PDF, A4, print-ready. Twenty genuinely different versions, so you already have a fresh sheet for every class, every resit and every homework. Licensed for the purchasing teacher and their own classes.

Dijkstra’s algorithm practice for AQA A Level Computer Science (7517): twenty different worksheets on the shortest path algorithm, each with a complete answer key. Every worksheet is built on a different weighted network. That is the point of the pack: you can set one sheet in class, a second for homework and a third for a resit without any two students ever holding the same questions, and without drawing new networks yourself at eleven o’clock at night. WHAT YOU GET 20 worksheets, 3 pages each, numbered 01 to 20 20 matching answer keys A contents table listing the number of vertices and the mark total of every sheet, so you can pick a six-vertex network for a ten-minute starter or a nine-vertex one for a full period WHAT IS ON EVERY SHEET Question 1 asks students to trace the algorithm: one row per vertex settled, recording every tentative distance and the vertex it was reached from, written as a subscript. Question 2 asks for the length of the shortest path and then for the path itself, read back off the completed table - the step most students never practise and most lose marks on. Question 3 asks why the distance to a settled vertex can never be improved by a later step, for a typical application of shortest path algorithms, and one further question that varies from sheet to sheet.

Graph traversal practice for AQA A Level Computer Science (7517): twenty different worksheets on breadth-first and depth-first search, each with a complete answer key. Every worksheet is built on a different graph. That is the point of the pack: you can set one sheet in class, a second for homework and a third for a resit without any two students ever holding the same questions, and without having to invent new graphs yourself at eleven o’clock at night. WHAT YOU GET 20 worksheets, 3 pages each, numbered 01 to 20 20 matching answer keys, 2 pages each A contents table listing the size and mark total of every sheet, so you can pick a short one for a cover lesson or a longer one for a full period WHAT IS ON EVERY SHEET Question 1 asks students to complete a trace table for a breadth-first traversal: the node removed from the queue, the state of the queue after each step, and the running visit order. Question 2 does the same for depth-first search, including the backtracking steps that most students forget. Question 3 shows a piece of pseudocode and asks which traversal it implements, and for a typical application of it. The first row of each trace table is completed for students, which removes any doubt about where the trace begins. Mark totals are printed at the top of each sheet and beside every question. WRITTEN FOR AQA, NOT ADAPTED FROM SOMEWHERE ELSE The pseudocode uses the conventions that appear in real 7517 question papers: the arrow assignment, SUBROUTINE and ENDSUBROUTINE, OUTPUT, FOR EACH … IN, and adjacency written as ConnectedNodes[N]. Helper subroutines are declared in prose before the code, exactly as AQA does. Question 3 asks for an application of the traversal rather than its time complexity, because that is what specification 4.3.1 actually requires. THE ANSWER KEYS DO SOMETHING UNUSUAL Textbooks disagree about how depth-first search is traced. These sheets use the alphabetically-first convention that mark schemes normally show, and state it plainly on the worksheet. But each answer key also lists the visit orders produced by the other two conventions in common use, with a note telling you to credit them in full. Whichever version your department teaches, you can mark with these keys without arguing with them. FORMAT PDF, A4, print-ready. You do not need to edit these: there are twenty genuinely different versions, so you already have a fresh sheet for every class, every resit and every homework. Licensed for the purchasing teacher and their own classes.

Two free sample worksheets on searching algorithms for AQA A Level Computer Science (7517), with full answer keys, so you can see exactly what the full pack contains before buying anything. Each sheet runs linear search, binary search and binary tree search on the same values, looking for the same target, so the three counts can be compared directly. The midpoint rule is printed on the sheet - (Bottom + Top) DIV 2, rounded down - so the trace has exactly one correct answer. The last question asks for the time complexity of all three algorithms and for the largest number of comparisons a binary search could need on a list of several thousand items: the specification asks students to trace AND to analyse, and both are on the sheet. These two sheets are not in the paid pack - they are extra, so nothing is wasted if you buy it afterwards. The full pack contains 20 worksheets and 20 answer keys, every one built on a different list. Search Tes for “AQA A Level Computer Science searching algorithms” to find it. If these are useful, a review is genuinely appreciated - it is the only way other teachers find resources like this.

Two free sample worksheets on binary tree traversal for AQA A Level Computer Science (7517), with full answer keys, so you can see exactly what the full pack contains before buying anything. Each sheet gives a binary tree as a diagram and as a table of nodes - Index, Left, Data, Right, with -1 for a missing child, the way AQA writes trees in its own papers. Question 1 asks for all three traversals, question 2 for the structure, and question 3 shows a recursive subroutine and asks which traversal it performs and what stops it calling itself. Neither tree has a traversal that comes out in alphabetical order, and no two of the three traversals are the same, so a student cannot arrive at a correct answer without actually walking the tree. These two sheets are not in the paid pack - they are extra, so nothing is wasted if you buy it afterwards. The full pack contains 20 worksheets and 20 answer keys, every one built on a different tree, and no two trees have the same shape. Search Tes for “AQA A Level Computer Science binary tree traversal” to find it. If these are useful, a review is genuinely appreciated - it is the only way other teachers find resources like this.

Two free sample worksheets on Dijkstra’s shortest path algorithm for AQA A Level Computer Science (7517), with full answer keys, so you can see exactly what the full pack contains before buying anything. Each sheet is built on its own weighted network. Question 1 is the trace table, one row per vertex settled, with tentative distances and the vertex each one was reached from. Question 2 asks for the length of the shortest path and for the path itself, read back off the completed table. Question 3 asks why a settled distance never changes, and for an application. These networks were generated so that the answer is never arguable: at every step exactly one unvisited vertex has the smallest tentative distance, and the shortest path to the target is unique. Whatever tie-breaking convention your department teaches, the answer key agrees with it. These two sheets are not in the paid pack - they are extra, so nothing is wasted if you buy it afterwards. The full pack contains 20 worksheets and 20 answer keys, every one built on a different network, which is what makes it usable for a whole class, a resit and a homework without any two students holding the same questions. Search Tes for “AQA A Level Computer Science Dijkstra shortest path” to find it.

Two free sample worksheets on graph traversal for AQA A Level Computer Science (7517), with full answer keys, so you can see exactly what the full pack contains before buying anything. Each sheet is built on its own graph. Question 1 is a breadth-first trace table, question 2 a depth-first trace table including the backtracking steps, and question 3 asks students to identify a traversal from pseudocode written in the style of real 7517 papers. These two sheets are not in the paid pack : they are extra, so nothing is wasted if you buy it afterwards. The full pack contains 20 worksheets and 20 answer keys, every one built on a different graph, which is what makes it usable for a whole class, a resit and a homework without any two students holding the same questions. Search Tes for “AQA graph traversal worksheets” to find it.

Assembly language practice for AQA A Level Computer Science (7517): twenty different programs to trace, each written in the instruction set AQA gives candidates in the exam, and each with a complete answer key. Most low-level programming resources teach the Little Man Computer. AQA does not use it. AQA publishes its own instruction set - LDR, STR, MOV, CMP, ADD, SUB, B and the conditional branches, the bitwise operators and the shifts - and hands it to candidates with the paper. A student who has only ever traced LMC meets that language for the first time in the exam. WHAT YOU GET 20 worksheets, 3 pages each, numbered 01 to 20 20 matching answer keys A contents table giving what each program does and how long its trace is, so you can pick one without opening all twenty WHAT IS ON EVERY SHEET The instructions that program uses are printed at the top of the sheet, in AQA’s own wording, so nothing has to be memorised to answer. Question 1 is the trace table: one row per instruction executed, recording the line number and every register, with the first row completed. Question 2 asks what the program leaves in memory. Question 3 runs it again with one value changed and asks what it leaves then - without tracing it a second time. Question 4 names the addressing mode of two operands and asks for the difference. Question 5 separates the opcode from the operands and asks why the program will not run on a different processor. Sheets run from 16 to 32 marks, depending on how long the trace is. TWENTY PROGRAMS THAT ACTUALLY DO SOMETHING Not random instructions. The programs add a list of values, multiply by repeated addition, divide by repeated subtraction, find the larger of two values, count values above a threshold, multiply and divide using shifts, and mask and combine bits. Eight shapes, different registers, addresses and constants each time, and traces from eight instructions to twenty-three - a short one is a starter, a loop of twenty fills a lesson. NOTHING IS LEFT TO THE TEXTBOOK Every value in every trace stays between 0 and 255, so no answer depends on how wide a register is - which the instruction set does not settle. The conventions the trace table depends on are printed on the sheet: one row per instruction executed including HALT, the line number in the Line column, and every register written in every row even when it has not changed. Every program halts, and every conditional branch is shown going both ways across the two runs. FORMAT PDF, A4, print-ready. Twenty genuinely different programs, so you already have a fresh sheet for every class, every resit and every homework. Written for AQA 7517. The instruction set is AQA’s own, so these sheets are not offered as an OCR or GCSE resource. Licensed for the purchasing teacher and their own classes.

Two free sample worksheets on sorting algorithms for AQA A Level Computer Science (7517), with full answer keys, so you can see exactly what the full pack contains before buying anything. Each sheet sorts the same eight values twice. The bubble sort is traced pass by pass, with the number of swaps in each; the merge sort is a diagram to complete, already split down to single values, with three rows of merging left blank. Question 3 asks for the time complexity of both and for the number of merge levels a much larger list would need. The bubble sort is printed in pseudocode on the worksheet, so the rule that stops it is in front of the student rather than in the teacher’s head, and the lists are eight values long, so every merge sort split is even. These two sheets are not in the paid pack - they are extra, so nothing is wasted if you buy it afterwards. The full pack contains 20 worksheets and 20 answer keys, every one built on a different list. Search Tes for “AQA A Level Computer Science sorting algorithms” to find it. If these are useful, a review is genuinely appreciated - it is the only way other teachers find resources like this.

Floating point binary practice for AQA A Level Computer Science (7517): twenty different worksheets on reading, writing and normalising floating point numbers, and on the error in a value the format cannot store, each with a complete answer key. AQA states in the specification that exam questions use a format in which both the mantissa and the exponent are two’s complement, but the number of bits changes from paper to paper: June 2018 used a 7-bit mantissa with a 5-bit exponent, June 2023 used 8 and 4. These sheets do the same. They use 8+4, 7+5 and 6+4, and every sheet prints its own format at the top of the page. WHAT YOU GET 20 worksheets, 2 pages each, numbered 01 to 20 20 matching answer keys A contents table listing the format and the final written question of each sheet, so you can pick one without opening all twenty WHAT IS ON EVERY SHEET Question 1 reads a floating point number and asks for the mantissa, the exponent and the value, in decimal. Question 2 goes the other way: a decimal value, written first in fixed point binary, then normalised into the boxes. Question 3 normalises two numbers - one with a positive mantissa and one with a negative mantissa. Question 4 gives a value the format cannot store exactly, together with the pattern the computer stores instead, and asks for the absolute and the relative error. Question 5 is a written question on precision, range, underflow, overflow, or why numbers are normalised at all. That covers specification 4.5.4.4 to 4.5.4.9. Sheets run from 21 to 22 marks. BOTH SIGNS, WHICH IS WHAT THE SPECIFICATION ASKS FOR The specification says students should “be able to normalise un-normalised floating point numbers with positive or negative mantissas”. Most resources work through the positive case and stop. Question 3 does both on every single sheet, and the answer key shows how many places the mantissa shifted and what the exponent became. NO QUESTION HAS TWO CORRECT ANSWERS Every value a student is asked to convert fits its format exactly. That is deliberate: when a value does not fit, the answer depends on whether your department rounds or truncates, and the AQA mark schemes themselves accept both. None of these sheets asks a student to make that choice. The one value that cannot be stored exactly is in question 4 - and there the stored pattern is given, so what is asked for is the error, not the rounding. Where the binary point sits, what counts as normalised, and how many bits go to each field are printed in the conventions at the top of every page, not assumed from a textbook. FORMAT PDF, A4, print-ready. No macros, nothing to enable, nothing that stops working when your IT policy changes. Twenty genuinely different versions, so you already have a fresh sheet for every class, every resit and every homework. Licensed for the purchasing teacher and their own classes.

Reverse Polish notation practice for AQA A Level Computer Science (7517): twenty different worksheets on converting to and from RPN and evaluating it with a stack, each with a complete answer key. The specification asks students to convert expressions from infix to Reverse Polish “and vice versa”. Most resources only show the first direction. Every sheet here does both: question 1 converts an infix expression to RPN, and question 2 converts a different RPN expression back to infix. WHAT YOU GET 20 worksheets, 2 pages each, numbered 01 to 20 20 matching answer keys A contents table listing the expression each sheet asks to convert, so you can pick one without opening all twenty WHAT IS ON EVERY SHEET Question 1 converts infix to Reverse Polish. Question 2 converts Reverse Polish back to infix, with brackets showing the order of evaluation. Question 3 evaluates an RPN expression with a stack in a trace table, one row per token read, with the first row completed. Question 4 asks why RPN needs no brackets and why interpreters store expressions in it. Sheets run from 17 to 19 marks. THREE PLACES A QUESTION COULD HAVE HAD TWO ANSWERS Precedence and associativity are stated in the conventions at the top of every sheet: times and divide before plus and minus, equal precedence left to right. The order of the operands of a subtraction - the slip where a b - is read as b - a - is stated too, with a worked example. And the expressions themselves are bracketed so that they say what they mean under that left-to-right rule. An expression like A * B * C looks harmless, but if the intended grouping is A * (B * C) then a student following the printed rule would produce a different RPN and be marked wrong for doing exactly what the sheet told them. Every expression in this pack is printed with the brackets that make its order unambiguous, and no more. Every expression to be evaluated was generated so that no intermediate result is negative or fractional: a student who reaches one knows they have slipped. WRITTEN FOR AQA The specification wording is “be able to convert simple expressions in infix form to Reverse Polish notation (RPN) form and vice versa”, with “eliminates need for brackets in sub-expressions” and “expressions in a form suitable for evaluation using a stack” in the notes beside it - AQA 7517, section 4.3.3, printed in the header of every page. Question 4’s answers use those words. This is an AQA topic: OCR H446 does not name Reverse Polish notation, so these sheets are shaped for AQA and are not offered as an OCR resource. FORMAT PDF, A4, print-ready. Twenty genuinely different versions, so you already have a fresh sheet for every class, every resit and every homework. Licensed for the purchasing teacher and their own classes.

Sorting algorithms practice for AQA A Level Computer Science (7517): twenty different worksheets on bubble sort and merge sort, each with a complete answer key. Every sheet sorts the same eight values twice. The bubble sort is traced pass by pass, and the merge sort is a diagram the student completes: the list comes already split down to single values, and the three rows of merging are the question. A student finishes the sheet having counted, say, seven passes and twenty-two swaps one way against three levels of merging the other - and question 3 then asks them to explain the gap. WHAT YOU GET 20 worksheets, 3 pages each, numbered 01 to 20 20 matching answer keys A contents table giving the number of passes, the number of swaps and the mark total of every sheet, so you can pick a four-pass list for a starter or a seven-pass one for a full lesson WHAT IS ON EVERY SHEET Question 1 gives the bubble sort in pseudocode and a table to complete, one row per pass, showing the list after that pass and the number of swaps in it. The first pass is done for the student. Question 2 is the merge sort diagram, with boxes sized to write in. Question 3 asks for the time complexity of both algorithms, for what that complexity means for a list twice as long, and for the number of levels of merging a much larger list would need. Sheets run from 17 to 20 marks, depending on how many passes the list happens to need. TWO CONVENTIONS, HANDLED TWO DIFFERENT WAYS Textbooks disagree on whether a bubble sort stops as soon as a pass makes no swaps or always runs the same number of passes. The two produce exactly the same list after every pass, so the trace table suits both; they differ only in how many passes get counted, and the stopping rule is printed in the pseudocode on the worksheet, so that question is answerable from the sheet. These worksheets never ask for the number of comparisons a bubble sort makes, because that one genuinely does depend on the version taught. They ask for the number of swaps, which does not: it is the number of pairs that started out in the wrong order, whatever route the algorithm takes. For merge sort, each list is eight values long, so every split is even and the question of which half gets the odd item never arises. WRITTEN FOR AQA The specification asks students to “know and be able to trace and analyse the time complexity of the bubble sort algorithm” and the same for merge sort - AQA 7517, section 4.3.5, printed in the header of every page. The pseudocode follows AQA’s own written conventions: the arrow for assignment, FOR … TO, LEN for the length of an array, and arrays indexed from 0. FORMAT PDF, A4, print-ready. Twenty genuinely different versions, so you already have a fresh sheet for every class, every resit and every homework. Licensed for the purchasing teacher and their own classes.

Two free sample worksheets on Reverse Polish notation for AQA A Level Computer Science (7517), with full answer keys, so you can see exactly what the full pack contains before buying anything. Each sheet converts an infix expression to RPN, converts a different RPN expression back to infix - the “and vice versa” the specification asks for - and evaluates an RPN expression with a stack, one row per token read. The last question asks why RPN needs no brackets. Precedence, the order of the operands of a subtraction and which end of a written stack is the top are all stated on the sheet, so each question has one correct answer. These two sheets are not in the paid pack - they are extra, so nothing is wasted if you buy it afterwards. The full pack contains 20 worksheets and 20 answer keys, every one on different expressions. Search Tes for “AQA A Level Computer Science reverse Polish notation” to find it. If these are useful, a review is genuinely appreciated - it is the only way other teachers find resources like this.

Two free sample worksheets on assembly language for AQA A Level Computer Science (7517), with full answer keys, so you can see exactly what the full pack contains before buying anything. Each sheet gives a short program written in the instruction set AQA hands to candidates in the exam - not the Little Man Computer, which shares none of its mnemonics. The instructions the program uses are printed at the top of the sheet in AQA’s own wording. Question 1 is the trace table, one row per instruction executed, with the first row completed. Question 2 asks what the program leaves in memory, and question 3 runs it again with one value changed. Question 4 names the two addressing modes, and question 5 separates the opcode from the operands. Every value stays between 0 and 255, so no answer depends on how wide a register is, and the conventions the trace table needs are printed on the sheet. These two sheets are not in the paid pack - they are extra, so nothing is wasted if you buy it afterwards. The full pack contains 20 worksheets and 20 answer keys, on twenty different programs. Search Tes for “AQA A Level Computer Science assembly language” to find it. If these are useful, a review is genuinely appreciated - it is the only way other teachers find resources like this.

Two free sample worksheets on floating point binary for AQA A Level Computer Science (7517), with full answer keys, so you can see exactly what the full pack contains before buying anything. Each sheet reads a floating point number, writes a decimal value back into the format, normalises one number with a positive mantissa and one with a negative mantissa - the “positive or negative mantissas” the specification asks for - and works out the absolute and relative error of a value the format cannot store exactly. The format is printed on the sheet: how many bits of mantissa and exponent, that both are two’s complement, where the binary point sits, and what counts as normalised. Every value to be converted fits its format exactly, so no answer depends on whether your department rounds or truncates. These two sheets are not in the paid pack - they are extra, so nothing is wasted if you buy it afterwards. The full pack contains 20 worksheets and 20 answer keys, on different formats and different numbers. Search Tes for “AQA A Level Computer Science floating point binary” to find it. If these are useful, a review is genuinely appreciated - it is the only way other teachers find resources like this.