9618 Computer Science June 2024 Question paper 22

1 (a) The following table contains pseudocode examples.

Each example may contain statements that relate to one or more of the following: • selection • iteration (repetition) • input/output.

Complete the table by placing one or more ticks (3) in each row. Pseudocode example Selection Iteration Input/Output FOR Index 1 TO 10 Data[Index] 0 NEXT Index WRITEFILE ThisFile, "****" UNTIL Level > 25 IF Mark > 74 THEN READFILE OldFile, Data ENDIF

[4]

(b) Program variables have data types as follows: Variable Data type MyChar CHAR MyString STRING MyInt INTEGER

Complete the table by filling in each gap with a function (from the insert) so that each expression is valid. Expression MyInt (3.1415926) MyChar ("Elwood", 3, 1) MyString ( (27.509)) MyInt ( ("ABC123", 3))

[4]

(c) The variables given in part (b) are chosen during the design stage of the program development life cycle.

The choices are to be documented to simplify program maintenance.

State a suitable way of documenting the variables and give one piece of information that should be recorded, in addition to the data type [2]

4 A triangle has sides of length A, B and C.

C A B

In this example, A is the length of the longest side.

This triangle is said to be right‑angled if the following equation is true:

A × A = (B × B) + (C × C)

A procedure will be written to check whether three lengths represent a right‑angled triangle.

The lengths will be input in any sequence.

The procedure IsRA() will: • prompt and input three integer values representing the three lengths • test whether the three lengths correspond to the sides of a right‑angled triangle • output a suitable message.

The length of the longest side may not be the first value input.

Write pseudocode for the procedure IsRA() [5]

2 A program is being developed.

(a) An algorithm for part of the program will: • input three numeric values and assign them to identifiers Num1, Num2 and Num3 • assign the largest value to variable Ans • output a message giving the largest value and the average of the three numeric values.

Assume the values are all different and are input in no particular order.

Complete the program flowchart on page 5 to represent the algorithm. START END INPUT Numl, Num2, Num3 Yes No

[5]

(b) A different part of the program contains an algorithm represented by the following program flowchart:

START END Set Flag to GetStat() Set Port to 1 Is Flag = TRUE ? Is Port = 4 ? Yes No No Yes CALL Reset(Port) Set Port to Port + 1

Write pseudocode for the algorithm [5]

3 A factory needs a program to help manage its production of items.

Data will be stored about each item.

The data for each item will be held in a record structure of type Component.

The programmer has started to define the fields that will be needed as shown in the table. Field Example value Comment Item_Num 123478 a numeric value used as an array index Reject FALSE TRUE if this item has been rejected Stage 'B' a letter to indicate the stage of production Limit_1 13.5 any value in the range 0 to 100 inclusive Limit_2 26.4 any value in the range 0 to 100 inclusive

(a) (i) Write pseudocode to declare the record structure for type Component [4]

(ii) A 1D array Item of 2000 elements will store the data for all items.

Write pseudocode to declare the Item array [2]

(b) State three benefits of using an array of records to store the data for all items. 1 2 3 [3]

5 A program is being designed in pseudocode.

The program contains a global 1D array Data of type string containing 200 elements.

The first element has the index value 1.

A procedure Process() is written to initialise the values in the array:

PROCEDURE Process(Label : STRING)

DECLARE Index : INTEGER

Index 0

INPUT Data[Index]

WHILE Index < 200

Index

Index + 1

CASE OF (Index MOD 2)

  0 : Data[Index]

TO_UPPER(Label)

  1 : Data[Index]

TO_LOWER(Label)

  OTHERWISE : OUTPUT "Alarm 1201"

ENDCASE

NEXT Index

OUTPUT "Completed " & Index & " times"

ENDPROCEDURE

(a) (i) The pseudocode contains two syntax errors and one other error.

Identify the errors. Syntax error 1 Syntax error 2 Other error [3]

(ii) The procedure contains a statement that is not needed.

Identify the pseudocode statement and explain why it is not needed. Statement Explanation [2]

(b) After correcting all syntax errors, the pseudocode is translated into program code which compiles without generating any errors.

When the program is executed it unexpectedly stops responding.

Identify the type of error that has occurred [1]

6 A music player stores music in a digital form and has a display which shows the track being played.

(a) Up to 16 characters can be displayed. Track titles longer than 16 characters will need to be trimmed as follows: • Words must be removed from the end of the track title until the resulting title is less than 14 characters. • When a word is removed, the space in front of that word is also removed. • Three dots are added to the end of the last word displayed when one or more words have been removed.

The table below shows some examples: Original title Display string 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Bat out of Hull B a t o u t o f H u l l Bohemian Symphony B o h e m i a n . . . Paperbook Writer P a p e r b o o k W r i t e r Chris Sings the Blues C h r i s S i n g s . . . Green Home Alabama G r e e n H o m e . . .

A function Trim() will: • take a string representing the original title • return the string to be displayed.

Assume: • Words in the original title are separated by a single space character. • There are no spaces before the first word or after the last word of the original title. • The first word of the original title is less than 14 characters.

Write pseudocode for the function Trim() [7]

(b) Music is stored as a sequence of digital samples.

Each digital sample is a denary value in the range 0 to 99999999 (8 digits).

The samples are to be stored in a text file. Each sample is converted to a numeric string and 32 samples are concatenated (joined) to form a single line of the text file.

Each numeric string is 8 characters in length; leading ‘0’ characters are added as required.

Example:

Sample 1 2 3 32 Denary value String 456 48 37652 "00000456" "00000048" "00037652" 673 "00000673"

The example samples will be stored in the text file as a single line:

"000004560000004800037652...00000673"

(i) Identify one drawback of adding leading ‘0’ characters to each numeric string [1]

(ii) Suggest an alternative method of storing the samples which does not involve adding leading ‘0’ characters but which would still allow each individual sample to be extracted [1]

(iii) State one drawback of the alternative method given in part (b)(ii) [1]

7 A fitness club has a computerised membership system.

The system stores information for each club member: name, home address, email address, mobile phone number, date of birth and exercise preferences.

Many classes are full, and the club creates a waiting list for each class. The club adds details of members who want to join a class that is full to the waiting list for that class.

When the system identifies that a space is available in one of the classes, a new module will send a text message to each member who is on the waiting list.

(a) Decomposition will be used to break the new module into sub‑modules (sub‑problems).

Identify three sub‑modules that could be used in the design and describe their use. Sub‑module 1 Use Sub‑module 2 Use Sub‑module 3 Use [3]

(b) A different part of the program is represented by the following state‑transition diagram. S1 START S4 S3 Input-B | Output-W Input-A | Output-X Input-B | Output-Y Input-A | Output-W Input-B Input-B Input-A Input-A S2 S5

(i) Complete the table to show the inputs, outputs and next states.

Assume that the current state for each row is given by the ‘Next state’ on the previous row. For example, the first Input‑A is made when in state S1.

If there is no output for a given transition, then the output cell should contain ‘none’.

The first two rows have been completed. Input Output Next state S1 Input‑A none S3 Output‑W none Input‑B Input‑A S4

[5]

(ii) Identify the input sequence that will cause the minimum number of state changes in the transition from S1 to S4 [1]

8 A teacher is designing a program to process pseudocode projects written by her students.

Each student project is stored in a text file.

The process is split into a number of stages. Each stage performs a different task and creates a new file.

For example: File name Comment MichaelAday_src.txt Student project file produced by student Michael Aday MichaelAday_S1.txt File produced by stage 1 MichaelAday_S2.txt File produced by stage 2

(a) Suggest a reason why the teacher’s program has been split into a number of stages and give the benefit of producing a different file from each stage. Reason Benefit [2]

(b) The teacher has defined the first program module as follows: Module Description DeleteSpaces() • called with a parameter of type string representing a line of pseudocode from a student’s project file • returns the line after removing any leading space characters The following example shows a string before and after the leading spaces have been removed: Before: " IF X2 > 13 THEN" After: "IF X2 > 13 THEN"

Complete the pseudocode for module DeleteSpaces().

FUNCTION DeleteSpaces(Line : STRING) RETURNS STRING ENDFUNCTION [6]

(c) Two modules are defined: Module Description DeleteComment() (already written) • called with a parameter of type string representing a line of pseudocode from a student’s project file • returns the line after removing any comment Stage_2() • called with two parameters: ○ a string representing an input file name ○ a string representing an output file name • copies each line from the input file to the existing output file having first removed all leading spaces and comments from that line • does not write blank lines to the output file • outputs a final message giving the number of blank lines removed

Write pseudocode for module Stage_2().

Modules DeleteComment() and DeleteSpaces() must be used in your solution [8]