9618/23 · Oct/Nov 2025
Download PDFA user requires a program that implements complex data encryption to a recognised international standard. A programmer has started the design of the program.
The programmer decides to use a library routine to provide part of the solution. One reason for this is that library routines may perform functions that the programmer is unable to program themselves. State three other benefits of using library routines in the development of the program.
The programmer has identified a different part of the algorithm that would be appropriate to implement as a subroutine (a procedure or a function); no suitable library routine exists for this part. State two reasons why the programmer may decide to use a subroutine.
A function header in pseudocode is defined as: FUNCTION Pass2(Count : INTEGER) RETURNS BOOLEAN Complete the table by describing the terms used in the function header. The first row has been completed. Term | Description Pass2 | the name of the function Count | BOOLEAN |
Variables in the program have example values: Variable | Example value DoB | 23/6/2011 Multiplier | 2.5 AddressLine[1] | "35 Lincoln Avenue" Complete the table by evaluating each expression using the example values: Expression | Evaluates to LENGTH(NUM_TO_STR(Multiplier)) | MONTH(DoB) > 4 | 15 + STR_TO_NUM(MID(AddressLine[1], 2, 1)) |
A program contains a global 1D array of type STRING containing 65 elements. An existing text file is used to store the data in the array. Only non-blank elements (those that do not contain an empty string) are written to the text file. An algorithm will: • write the first element of the array as a new line in the text file • continue until all elements have been written, each to a new line of the text file. Stepwise refinement is applied to the algorithm. Describe up to six steps for this algorithm that could be used to produce pseudocode. Do not use pseudocode statements in your answer.
Iteration is one programming construct. Identify one other programming construct that will be required when the algorithm from part (a) is converted into pseudocode and explain how it is used.
A program uses a stack to hold up to 30 integer values. The stack is implemented using a global integer variable and a global 1D array. The array is declared in pseudocode: DECLARE ThisStack : ARRAY[1:30] OF INTEGER Stack design notes: • The global variable SP acts as a stack pointer. SP contains the array index of the last value pushed onto the stack. • If the stack is empty, then SP is assigned the value zero. • The first item added to the stack will be stored in ThisStack[1] • SP is incremented each time an item is added to the stack. A function Pop() is written to remove an item from ThisStack. The function returns an item of type PopData which is defined in pseudocode: TYPE PopData DECLARE Data : INTEGER DECLARE Exists : BOOLEAN ENDTYPE The value removed from the stack is assigned to Data and Exists is set to TRUE. If it is not possible to remove a value from the stack, then Exists is set to FALSE Complete the pseudocode for Pop() FUNCTION Pop() RETURNS PopData DECLARE ThisPop : ............................................... IF ............................................... THEN PopData.Exists ← ............................................... // Stack is empty ELSE PopData.Data ← ............................................... PopData.Exists ← ............................................... SP ← ............................................... ENDIF RETURN ThisPop ENDFUNCTION
A program contains a global 1D array Data containing 20 elements of type INTEGER A global string NumString represents a sequence of three-digit numbers, separated by commas. For example: "101,456,219,754,328" The string contains at least four three-digit numbers. The total number of three-digit numbers in the string is unknown. A procedure Store() will: • extract one three-digit number at a time from NumString • convert each of the three-digit numbers extracted to an integer and assign this to the next array element, starting from index 1 • end when all three-digit numbers have been stored, or when the array is full. Complete the pseudocode for Store() All local variables used must be declared. PROCEDURE Store() ENDPROCEDURE
A global 1D array Num of integers contains four elements. A program assigns values to these elements as shown: Num[1] ← 1 Num[2] ← 2 Num[3] ← 5 Num[4] ← 3 A procedure Process() manipulates the values in the array. The procedure is written in pseudocode: PROCEDURE Process(Start : INTEGER) DECLARE CaseVar, Index, Count : INTEGER Index ← Start Count ← 0 WHILE Count <= 20 CaseVar ← Num[Index] CASE OF CaseVar 1 : Num[Index] ← Num[Index] + Index //clause one Index ← Index + 1 Count ← Count + 1 2 : Num[Index] ← Num[Index] + Index //clause two Index ← Index + 2 Count ← Count + 2 3 : Num[Index] ← Num[Index] * 2 //clause three Index ← Index + 3 Count ← Count - 1 4 : Count ← Count + 4 //clause four OTHERWISE : Count ← 20 ENDCASE Index ← (Index MOD 4) + 1 ENDWHILE ENDPROCEDURE
Complete the trace table by dry running the procedure when it is called in the statement: CALL Process(1)
As a reminder, the CASE structure in the pseudocode is: CASE OF CaseVar 1 : Num[Index] ← Num[Index] + Index //clause one Index ← Index + 1 Count ← Count + 1 2 : Num[Index] ← Num[Index] + Index //clause two Index ← Index + 2 Count ← Count + 2 3 : Num[Index] ← Num[Index] * 2 //clause three Index ← Index + 3 Count ← Count - 1 4 : Count ← Count + 4 //clause four OTHERWISE : Count ← 20 ENDCASE The CASE structure could be optimised by combining two existing clauses. Identify the CaseVar values for these two existing clauses.
Write pseudocode for a single clause to replace the two clauses identified in (b) (i).
Students are learning about a simple check digit method for data validation. In this method, a single check digit is appended to the end of an original number to give a new number. The students are studying a method which: • calculates the sum of all the digits in the original number • uses integer division to calculate the remainder when the sum is divided by 10 • uses the remainder as the check digit • appends the check digit to the original number, creating the new number. For example: original number | 4162 sum of all digits | 4 + 1 + 6 + 2 = 13 remainder when the sum is divided by 10 using integer division | 3 new number | 41623 The original number is always at least three digits in length. When the new number is input, the check digit is used to validate the new number.
A function Generate() is written to take an original number as a parameter and to return the check digit. Outline a test plan that could be used to fully test function Generate() Assume that the parameter is valid.
A function CheckNumber() will take an integer value and return the Boolean value TRUE if the check digit is correct, otherwise return FALSE Write pseudocode for the function CheckNumber() Assume that the parameter is valid.
There are several different ways to express an algorithm during the design of a program.
One part of the program contains an algorithm which is represented by a state-transition diagram. The table shows the inputs, outputs and states for the algorithm: Current state | Input | Output | Next state S1 | A1 | | S2 S2 | A2 | X4 | S3 S3 | A1 | X1 | S3 S3 | A2 | X1 | S3 S3 | A3 | X3 | S4 S3 | A4 | | S2 S4 | A3 | X4 | S5 S4 | A4 | X4 | S5 S4 | A1 | | S2 Complete the state-transition diagram to represent the information given in the table:
A structure chart is used to document a different part of the program, made up of five modules. Program notes: • module Setup calls either module Restart, or module Confirm • module Confirm takes a string as a parameter and returns an integer • module Modify has no parameters and returns a Boolean • module Update takes a string as a parameter • module Restart repeatedly calls module Update followed by module Modify • module Restart takes a string as a parameter that is passed by reference. Draw a structure chart to represent the relationship between the five modules, including all parameters and return values.
A program is being developed to manage student book loans from a college library. The programmer has defined a record type to define each loan. The data items are: Data item | Data type | Comment StudentID | STRING | the unique ID of the student who has borrowed the book The first three characters of a StudentID represent a tutor ID. Each student has one tutor. BookID | STRING | the unique ID of the book being borrowed OnLoan | BOOLEAN | TRUE if the book has not been returned The programmer has defined a global array Loan to store 8000 loan records. There are more elements in the array than books in the library. Unused elements have the StudentID set to an empty string. These may occur anywhere in the array. The programmer has defined a program module: Module | Description LoanStatus() | • called with two parameters of type STRING representing a StudentID and a BookID • outputs a message saying whether a given loan has been returned or not • outputs a warning message if a record of the given loan is not found
Write efficient pseudocode for the module LoanStatus() Assume that each combination of StudentID and BookID can occur only once.
A second module is defined: Module | Description LoansPerTutor() | • called with a parameter of type STRING representing a tutor ID (as a reminder, the first three characters of a StudentID represent a tutor ID) • returns an integer value representing the number of books currently on loan to students who have the given tutor Reminder: unused elements have the StudentID set to an empty string. These may occur anywhere in the array. Write pseudocode for the module LoansPerTutor()
It is decided to mark as unused all records for book loans that have been returned. The data for these records will first be written to a new text file for archive purposes. The archive program will automatically generate a meaningful filename each time it is run. Outline a meaningful format to use for the filename.
There is a problem that will need to be overcome before the data items can be written to a text file. As a reminder, the data items are: Data item | Data type | Comment StudentID | STRING | the unique ID of the student who has borrowed the book The first three characters of a StudentID represent a tutor ID. Each student has one tutor. BookID | STRING | the unique ID of the book being borrowed OnLoan | BOOLEAN | TRUE if the book has not been returned Explain the problem.
One way of storing the data items in a text file is to store each data item on a separate line. Identify one benefit and one drawback of this way of storing the data.