Summer 2025 Paper 23 · Question 8 | 15-Mark Masterclass

From null strings to a searchable video library.

Build the solution in a sensible order: understand the two record arrays, plan the menu loop, initialise Video[] once and Results[] before every search, add each video into the first free slot, copy every title match into Results[] and report a miss gracefully. Learn the reasoning before revealing the complete program.

2D string arraysNull-string initialisationValidated menu loopFirst-free-slot insertSearch and copy matches15 marks

Cambridge IGCSE Computer Science · 0478/23 · Question 8

A collector needs a video library system for a collection of videos stored on 4K Blu-ray discs, standard Blu-ray discs, DVD, or as digital downloads.

The two-dimensional (2D) array Video[] is used to store, for each video item, the title, the format of the video (4K Blu-ray disc, standard Blu-ray disc, DVD, or digital download), the year it was released stored as a string and a storage code to represent where the video can be found in the collection, for example:

`Video[1,1]`	is "Macbeth"
`Video[1,2]`	is "digital download"
`Video[1,3]`	is "2015"
`Video[1,4]`	is "DG276"

The two-dimensional (2D) array Results[] is used to store the results of a search to find a specific video. The search uses the video title, and if the video is found, its data is copied from the array Video[] to the array Results[]. The search continues and if other videos with the same title are found, this data is also copied to the array Results[]. The search ends when the end of the data is reached.

Write a program that meets the following requirements:

The video library array needs to be initialised with the null string (""), allowing for up to 10 000 records. The array Results[] must be initialised before every search with the null string and must be able to hold up to 20 search results with the same title.
Create a menu to add a new video to the library to search for an existing video by title, or to stop, with validation of the input.
When the user enters a new video, the following data is stored in the first available location of the relevant array:
- video title
- format (4K Blu-ray disc, standard Blu-ray disc, DVD, digital download)
- year of release as string
- storage code
Allow input of data for another video if required.
When searching for an existing video, if a match is found, transfer all the data for that video into the array Results[], and continue to search until all videos with the same title have been found.
Output the results from the array Results[]
If the video title is not found, output a suitable message.
The system returns to the menu after completing the input or the output, until the user chooses to stop.

You must use pseudocode or program code and add comments to explain how your code works.

You do not need to declare any arrays, variables or constants. You may assume that this has already been done.

All inputs and outputs must contain suitable messages.

// One-off: fill Video[] with the null string // Menu loop: show S / A / X and validate the choice // A: input four strings, store in the first free // slot, allow another video // S: clear Results[], input the title, copy every // matching record, output Results[] or not-found // Repeat until the user chooses X

// Already declared by the system: // Video[10000, 4] - title, format, year (string), storage code // Results[20, 4] - up to 20 search matches // Variables used by the program: // MenuChoice - validated menu choice (S / A / X) // MoreVideos - Y/N answer after each add // SearchTitle - title typed by the user // MatchCount - matches copied into Results[] // VideoRow - library row being scanned // ResultRow - Results[] row being cleared or output // NextSlot - first free library position

// One-off: the library starts completely empty FOR RowCounter ← 1 TO 10000 FOR ColCounter ← 1 TO 4 Video[RowCounter, ColCounter] ← "" NEXT ColCounter NEXT RowCounter // Before every search: Results[] is emptied again FOR ResultRow ← 1 TO 20 FOR ResultCol ← 1 TO 4 Results[ResultRow, ResultCol] ← "" NEXT ResultCol NEXT ResultRow

REPEAT REPEAT OUTPUT "Enter S to search, A to add a video, X to stop" INPUT MenuChoice IF MenuChoice <> "S" AND MenuChoice <> "A" AND MenuChoice <> "X" THEN OUTPUT "Invalid choice - please enter S, A or X" ENDIF UNTIL MenuChoice = "S" OR MenuChoice = "A" OR MenuChoice = "X" IF MenuChoice = "A" THEN // add-a-video code (Stage 5) ENDIF IF MenuChoice = "S" THEN // search code (Stage 6) ENDIF UNTIL MenuChoice = "X" // the user chooses to stop

// Inside the menu loop: IF MenuChoice = "A" THEN REPEAT NextSlot ← 1 WHILE Video[NextSlot, 1] <> "" DO NextSlot ← NextSlot + 1 ENDWHILE OUTPUT "Enter the video title" INPUT Video[NextSlot, 1] OUTPUT "Enter the format" INPUT Video[NextSlot, 2] OUTPUT "Enter the year of release" INPUT Video[NextSlot, 3] // stored as a string OUTPUT "Enter the storage code" INPUT Video[NextSlot, 4] OUTPUT "Video added in position ", NextSlot OUTPUT "Add another video? Enter Y or N" INPUT MoreVideos UNTIL MoreVideos <> "Y" ENDIF

// Inside the menu loop: IF MenuChoice = "S" THEN FOR ResultRow ← 1 TO 20 FOR ResultCol ← 1 TO 4 Results[ResultRow, ResultCol] ← "" NEXT ResultCol NEXT ResultRow OUTPUT "Enter the title to search for" INPUT SearchTitle MatchCount ← 0 VideoRow ← 1 WHILE Video[VideoRow, 1] <> "" DO IF Video[VideoRow, 1] = SearchTitle THEN MatchCount ← MatchCount + 1 FOR ColCounter ← 1 TO 4 Results[MatchCount, ColCounter] ← Video[VideoRow, ColCounter] NEXT ColCounter ENDIF VideoRow ← VideoRow + 1 ENDWHILE IF MatchCount > 0 THEN FOR ResultRow ← 1 TO MatchCount OUTPUT "Title ", Results[ResultRow, 1] OUTPUT "Format ", Results[ResultRow, 2] OUTPUT "Year of release ", Results[ResultRow, 3] OUTPUT "Storage code ", Results[ResultRow, 4] NEXT ResultRow ELSE OUTPUT "Video not found - no video is titled ", SearchTitle ENDIF ENDIF

// After the loop - the user chose X OUTPUT "Library closed" OUTPUT "Videos stored: ", NextSlot - 1 // Final bullet audit: // 1 null-string initialisation - Video[] once, // Results[] before every search // 2 validated menu S / A / X, looped // 3 add into first free slot, four fields, // another allowed // 4 every title match copied to Results[] // and output from it // 5 not-found message when MatchCount = 0

FOR RowCounter ← 1 TO 10000 // R1 - null strings, up to 10 000 records FOR ColCounter ← 1 TO 4 Video[RowCounter, ColCounter] ← "" NEXT ColCounter NEXT RowCounter REPEAT // R2 - the menu repeats until the user stops REPEAT OUTPUT "Enter S to search, A to add a video, X to stop" INPUT MenuChoice IF MenuChoice <> "S" AND MenuChoice <> "A" AND MenuChoice <> "X" THEN OUTPUT "Invalid choice - please enter S, A or X" ENDIF UNTIL MenuChoice = "S" OR MenuChoice = "A" OR MenuChoice = "X" IF MenuChoice = "A" THEN REPEAT // R3 - first available location, allow another NextSlot ← 1 WHILE Video[NextSlot, 1] <> "" DO // find the first free row NextSlot ← NextSlot + 1 ENDWHILE OUTPUT "Enter the video title" INPUT Video[NextSlot, 1] OUTPUT "Enter the format (4K Blu-ray disc, standard Blu-ray disc, DVD, digital download)" INPUT Video[NextSlot, 2] OUTPUT "Enter the year of release, e.g. 2015" INPUT Video[NextSlot, 3] // the year is stored as a string OUTPUT "Enter the storage code" INPUT Video[NextSlot, 4] OUTPUT "Video added in position ", NextSlot OUTPUT "Add another video? Enter Y or N" INPUT MoreVideos UNTIL MoreVideos <> "Y" ENDIF IF MenuChoice = "S" THEN FOR ResultRow ← 1 TO 20 // R1 - Results[] cleared before every search FOR ResultCol ← 1 TO 4 Results[ResultRow, ResultCol] ← "" NEXT ResultCol NEXT ResultRow OUTPUT "Enter the title to search for" INPUT SearchTitle MatchCount ← 0 VideoRow ← 1 WHILE Video[VideoRow, 1] <> "" DO // R4 - copy every matching record IF Video[VideoRow, 1] = SearchTitle THEN MatchCount ← MatchCount + 1 FOR ColCounter ← 1 TO 4 Results[MatchCount, ColCounter] ← Video[VideoRow, ColCounter] NEXT ColCounter ENDIF VideoRow ← VideoRow + 1 ENDWHILE IF MatchCount > 0 THEN // output the results from Results[] FOR ResultRow ← 1 TO MatchCount OUTPUT "Match ", ResultRow, ": ", Results[ResultRow, 1], ", ", Results[ResultRow, 2], ", ", Results[ResultRow, 3], ", ", Results[ResultRow, 4] NEXT ResultRow ELSE // R5 - suitable not-found message OUTPUT "Video not found - no video is titled ", SearchTitle ENDIF ENDIF UNTIL MenuChoice = "X"

Band	What the descriptor means
0	No creditable response.
1–3	At least one programming technique is used. Some data is stored, but not appropriately. Any use of iteration, selection, counting, totalling, input or output may be credited.
4–6	Some programming techniques are appropriate to the problem, with more than one technique applied. Some data structures are appropriate and store some of the required data.
7–9	The full range of techniques needed by the scenario is used appropriately. The chosen data structures are appropriate and store all the required data.

Band	What the descriptor means
0	No creditable response.
1–2	Program seen without relevant comments. Some identifier names and some data-structure names are appropriate. The solution may be illogical or inaccurate in many places, but attempts at least one requirement.
3–4	Program seen with some relevant comments. The majority of identifiers and most data-structure names are meaningful. Parts may be illogical or inaccurate, but most requirements are met.
5–6	The program is fully commented. Suitable identifiers are meaningful throughout, and all data structures have meaningful names. The program is logical and accurate and meets all requirements; minor syntax errors are ignored.

Stage	Mark-scheme link	AO2 evidence	AO3 evidence
1 · Decode	R1–R5	Identifies initialisation, menu, add and search as separate jobs.	Establishes the loop-first order and the comment plan.
2 · Data	Required data structures	Video[] and Results[] with four string columns; counters and flags chosen.	Meaningful identifiers: MatchCount, NextSlot, MenuChoice.
3 · Initialise	R1	Video[] cleared once; Results[] cleared before every search.	Nested loops using the question’s own bounds (10 000, 20).
4 · Menu	R2	Validated S/A/X menu inside a loop until stop.	Accurate REPEAT–UNTIL and WHILE conditions.
5 · Add video	R3	First-free-slot scan and four string inputs; another-video loop.	INPUT into array elements with suitable prompts.
6 · Search	R1, R4, R5	Every match copied into Results[]; output loop; not-found branch.	Exact string equality and a correct write pointer.
7 · Summary	R2, R5	Menu returns after every action; stop ends the session.	Bullet audit, closing message and assumed declarations.

From null strings to a searchable video library.

Learning targets

01 · Understand

02 · Construct

03 · Complete

Read the whole question first

Before you move on

Decode the requirements

🧠 Step-by-step thinking

❓ Guiding questions – think before revealing

📖 Detailed explanation

⚠️ Common mistakes

💡 Exam hack / tip

Plan the data and identifiers

🧠 Step-by-step thinking

❓ Guiding questions – think before revealing

📖 Detailed explanation

⚠️ Common mistakes

💡 Exam hack / tip

Initialise the library and the results array

🧠 Step-by-step thinking

❓ Guiding questions – think before revealing

📖 Detailed explanation

⚠️ Common mistakes

💡 Exam hack / tip

Build the validated menu loop

🧠 Step-by-step thinking

❓ Guiding questions – think before revealing

📖 Detailed explanation

⚠️ Common mistakes

💡 Exam hack / tip

Add a video to the first free slot

🧠 Step-by-step thinking

❓ Guiding questions – think before revealing

📖 Detailed explanation

⚠️ Common mistakes

💡 Exam hack / tip

Search by title and copy every match

🧠 Step-by-step thinking

❓ Guiding questions – think before revealing

📖 Detailed explanation

⚠️ Common mistakes

💡 Exam hack / tip

Close the loops and check every bullet

🧠 Step-by-step thinking

❓ Guiding questions – think before revealing

📖 Detailed explanation

⚠️ Common mistakes

💡 Exam hack / tip

What does a high-level response look like?

How the seven stages contribute

Final self-check

Complete solution

Why this is a complete response

What to check before submitting

Visualisation: watch the library session run.

Sample input → expected results

Input array Video[,] · first 8 of 10 000 rows

Expected session results After both searches and the add

Execution trace

Initialisation

Live variable values

Library and search counters