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A linear search and a bubble sort are standard methods of solution. Fifty numbers are already stored in the array Values[1:50]. Write an algorithm in pseudocode to input a number, MyNumber, and use a linear search to test if that number is stored in the array. If the number is found in the array, the position in the
A linear search and a bubble sort are standard methods of solution. Fifty numbers are already stored in the array Values[1:50]. Write an algorithm in pseudocode to input a number, MyNumber, and use a linear search to test if that number is stored in the array. If the number is found in the array, the position in the
array is output. If the number is not found in the array, “Not found” is output.
array is output. If the number is not found in the array, “Not found” is output.
INPUT MyNumber
Location<--0
FOR Index<--1 TO 50
IF Values[Index] = MyNumber
THEN
Location Index
ENDIF
NEXT Index
IF Location = 0
THEN
OUTPUT "Not found"
ELSE
OUTPUT Location
ENDIF
Write an algorithm in pseudocode to sort the array Values[1:50] into ascending order using a bubble sort.
Write an algorithm in pseudocode to sort the array Values[1:50] into ascending order using a bubble sort.
Last <--50
Repeat
Swap FALSE
FOR Index 1 TO Last - 1
IF Values[Index] > Values[Index + 1]
THEN
Temp<--Values[Index]
Values[Index]<--Values[Index + 1]
Values[Index + 1] <--Temp
Swap TRUE
ENDIF
NEXT
Last<--Last - 1
UNTIL NOT Swap or Last = 1
Describe two types of iteration that a programmer can use whilst writing a program.
Describe two types of iteration that a programmer can use whilst writing a program.
count controlled, the number of iterations is pre-determined
pre-condition, checks condition at the start of loop // loop may not iterate
post-condition, checks condition at end of loop // loop always iterates at least once (1)
Describe what is meant by abstraction.
Describe what is meant by abstraction.
simplifying the problem
removing unnecessary details from the problem // selecting elements required
filtering out irrelevant characteristics from those elements
Identify all parts when a problem has been decomposed at the analysis stage.
Identify all parts when a problem has been decomposed at the analysis stage.
inputs // what is put into the system
processes // actions taken to achieve a result
outputs // what is taken out of the system
storage // what needs to be kept for future use
A satellite navigation system is an example of a computer system that is made up of sub-systems. Part of a satellite navigation system:
A satellite navigation system is an example of a computer system that is made up of sub-systems. Part of a satellite navigation system:
• allows the user to enter details for a new destination or select a previously saved destination
• allows the user to enter details for a new destination or select a previously saved destination
• displays directions in the form of a visual map or as a list. Draw a structure diagram for this part of the satellite navigation system.
• displays directions in the form of a visual map or as a list. Draw a structure diagram for this part of the satellite navigation system.
One mark for a hierarchical structure.
One mark for suitable names for the sub-systems.
One mark for identifiable inputs.
One mark for identifiable outputs
Satellite navigation system
Input destination
New destination
Saved destination
Output directions
Map
List
Describe two differences between local variables and global variables.
Describe two differences between local variables and global variables.
local variables - scope is a defined block of code/subroutine/procedure/function
global variables – scope is the whole program
local variables - value cannot be changed elsewhere in the program
global variables – value can be changed anywhere in the program
Describe what is meant by data validation.
Describe what is meant by data validation.
Validation is an automated check carried out by a computer
to make sure the data entered is sensible/acceptable/reasonable
Explain why validation and verification checks are needed when data is input. Include an example of each type of check in your answer.
Explain why validation and verification checks are needed when data is input. Include an example of each type of check in your answer.
One mark for explaining why a validation check is needed when data is input
To check that data is sensible / reasonable / meets required criteria
One mark for explaining why a verification check is needed when data is input
To check that data is not changed on entry
One mark for an example of a validation check
Range check // Length check // Type check
One mark for an example of a verification check
Double entry // Visual check
Explain why verification checks are used when data is input. Give two types of verification checks and state how each one can be used.
Explain why verification checks are used when data is input. Give two types of verification checks and state how each one can be used.
To ensure that data has been accurately copied // to ensure that changes have not been made to the values originally
intended when data is copied
... from one source to another
TYPES
Verification check 1 – Visual check
Use – the user looks through the data that has been entered and confirms that no changes have been made.
Verification check 2 – Double data entry
Use – data is entered twice, the two entries are compared and if they do not match, a re-entry is requested.
Describe the purpose of test data. Include an example of a type of test data in your answer.
Describe the purpose of test data. Include an example of a type of test data in your answer.
check that the program works as expected
check for logic/runtime errors
check that the program rejects any invalid data that is input
check that the program only accepts reasonable data
Example
Normal // erroneous // abnormal // extreme // boundary
Explain the purpose of the library routines DIV, ROUND, MOD and RANDOM
Explain the purpose of the library routines DIV, ROUND, MOD and RANDOM
DIV
To perform integer division
Meaning only the whole number part of the answer is retained
Example of DIV For example DIV(9,4) = 2
ROUND
To return a value rounded to a specified number of digits / decimal places
The result will either be rounded to the next highest or the next lowest value
... depending on whether the value of the preceding digit is >=5 or <5
Example of ROUND for example, ROUND(4.56, 1) = 4.6
MOD
To perform (integer) division when one number is divided by another
... and find the remainder
Allow example e.g. 7 MOD 2 = 1
RANDOM
To generate (pseudo) random numbers
...(usually) within a specified range
Allow example e.g. RANDOM() * 10 returns a random number between 0 and 10
Outline the role of procedures and functions in creating a program that is easier to maintain.
Outline the role of procedures and functions in creating a program that is easier to maintain.
One mark per mark point, max three
Procedures / functions divide the program into smaller manageable segments
... making it more readable / easier to understand / easier to debug
Procedures / functions with meaningful names help to provide documentation for the program / enable/help/provide
abstraction
Procedures and functions may be re-used (in the program / in other
State two features that should be included to create a maintainable program.
State two features that should be included to create a maintainable program.
Meaningful identifiers – to enable the programmer (or future programmers) to easily recognize the purpose of a variable / array / constant // to enable easy tracking of a variable / constant / array through the program
Use of comments – to annotate each section of a program so that a programmer can find specific sections / so that the programmer knows the purpose of that section of code
Procedures and functions
– to make programs modular and easier to update / add functionality
use indentation and white space
Give reasons for storing data in a file.
Give reasons for storing data in a file.
data is stored permanently
data can be moved to another computer
another copy of data can be made and stored//accessed elsewhere // backup copy
Describe a one-dimensional array. Include an example of an array declaration. Explain how indexing could be used to search for a value stored in a one-dimensional array.
Describe a one-dimensional array. Include an example of an array declaration. Explain how indexing could be used to search for a value stored in a one-dimensional array.
a list / one column of items
... of the same data type
... stored under a single identifier
... with a single index to identify each element
Declaration
Example: DECLARE MyArray[1:10] OF INTEGER
Indexing
using a counter to index the array
so that the same code can be repeatedly used to check every element // every element can be checked in a loop
There is a program that stores the following data:
There is a program that stores the following data:
• EmployeeID, an employee ID which must be two letters followed by 4 numbers, e.g. TY4587
• EmployeeID, an employee ID which must be two letters followed by 4 numbers, e.g. TY4587
• Manager, whether the employee is a manager or not
• Manager, whether the employee is a manager or not
• AnnualHoliday, number of whole days’ annual holiday
• AnnualHoliday, number of whole days’ annual holiday
• PayGrade, the employee’s pay grade which must be a single letter A–F
• PayGrade, the employee’s pay grade which must be a single letter A–F
Complete the following to identify:
Complete the following to identify:
• The most appropriate data type for each variable
• The most appropriate data type for each variable
• An appropriate validation check for each variable. You must use a different validation check for each variable.
• An appropriate validation check for each variable. You must use a different validation check for each variable.
EmployeeID String Length Check / Presence Check / Format Check / Type check
Manager Boolean Type Check / Presence Check
AnnualHoliday Integer Type Check / Range Check / Presence Check
PayGrade Char Presence Check / Length Check / Type Check
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