Data types and structures

Cambrdige AS level computer science 2025. Textbook references: Cambridge International AS and A level computer science coursebook Sylvia Langfield, David Duddell 2019 press ||| Cambrdige International AS and A Levels Computer science by David Wastson, Helen Williams press 2019

why are data types important

helps the computer and the user understand the information

what data type is for numbers

integer

what data type is for one letter or one symbol

char

what data type is for mainly words

string

what data type is for decimal

real

what data type is for yes and no or true and false

Boolean

what data type is for a specific date

date

what data type would you for your name

string

what data type would you use for the number of children in a class

integer

what data type would you use for the time taken to run a race

date/time

what data type would you use for whether a door is opened or closed

boolean

what data type would you use for your birthday

date

what is a record

composite date type comprising several related items

what is a random file

file that stores records at specific addresses that can be accessed directly

what is a binary file

where we store records serially or sequentially

what do we use files for

store and read lines of text

what do text files allow you to write

strings in serial or sequential manner

where can you append strings to a file

at the end of the file

what does this do(pseudocode): OPENFILE <filename> FOR WRITE

create a file and open it for writing

what does this do(pseudocode):OPENFILE <filename> FOR APPEND

open a file in append mode

what does this do(pseudocode): OPENFILE <filename> for read

open a file for reading

what does this do(pseudocode): OPENFILE <filename> FOR RANDOM

open a file for random acces

what does this do(pseudocode): CLOSEFILE <filename>

close a file

what does this do(pseudocode): PUTRECORD <filename>, <identifier>

write a record to a file

what does this do(pseudocode): GETRECORD <filename>, <identifier>

read a record from a file

what does this do(pseudocode): SEEK <filename>, <address>

move to a specific disk address within the file

what does this do(pseudocode): EOF(<filename>)

test for end of file

What is going on here?

Dim fileNum As Integer = FreeFile()
FileOpen(fileNum, "filename.txt", OpenMode.Output)

create a file and open for writing

What is going on here?

Dim fileNum As Integer = FreeFile()
FileOpen(fileNum, "filename.txt", OpenMode.Append) 
PrintLine(fileNum, "New data")

opening a file in append mode

What is going on here?

Dim fileNum As Integer = FreeFile()
FileOpen(fileNum, "filename.txt", OpenMode.Input)
Dim line As String
Do While Not EOF(fileNum)
    line = LineInput(fileNum) 
    Console.WriteLine(line) 
Loop

opening a file for reading

What is going on here?

Dim fileNum As Integer = FreeFile()
Dim recordLength As Integer = Len(New Student())
FileOpen(fileNum, "students.dat", OpenMode.Random, , , recordLength)

opening a file for random access

What is going on here?

FileClose(fileNum) 

closing a file

What is going on here?

Dim student As Student
student.Name = "Alice"
student.ID = 101
FilePut(fileNum, student, recordNumber)

writing a record to a file

What is going on here?

Dim student As Student
FileGet(fileNum, student, recordNumber) 
Console.WriteLine($"Name: {student.Name}, ID: {student.ID}")

reading a record from a file

What is going on here?

Seek(fileNum, address)

moving to a specific position (random access)

What is going on here?

If EOF(fileNum) Then
    Console.WriteLine("End of file reached.")
End If

testing for the end of a file

what does lineinput(filenum) do

reads one line

what is append mode

opening a file so that new data is added to the end of the existing content in the file

what is sequential file processing

a way of saving records on a disk before the program quits in order so you don’t lose the data

uses for append mode

saving user input over multiple sessions

what kind of array does random-access file processing use

fixed-length records

why does random-access file processing use fixed-length records

allows computer to directly calculate the position of any record in the file

what does random-access file processing do

store each record in a binary file as the record is created

what can a hashing function calculate

address from the record key and store the record at the calculated address

what does READ do in file handling

read data from the file

what does WRITE do in file handling

writes data to the file

what is the disadvantage of using WRITE when you opened a file

overwrites the data

what is a positive when using APPEND when opening a file

does not overwrite the data

what does APPEND do in file handling

adds data to the end of the file i

is a 1D array a list or table

list

is a 2D array a list or table

table

what is a flowline for

shows the process’ direction. connects two blocks

what is a data type

a classification attributed to an item of data which determine the types of value it can take and how it can be used

what is an identifier

a unique name applied to an item of data

what is a record data type

a composite data type comprising of several related items that may be of different data types

what is a composite data type

data type constructed using several of the basic data types available in a praticular language

what is an array

a data structure containing several elements of the same data type

what is an array index

a numerical indicator of an item of data' positions in an array

what is a lower bound

index of the first element in an array

what is an upper bound

the index of the last element in an array

what is linear search

a method of searching in which each element of an array is checked in order

what is bubble sort

method of sorting data in an array into ascending or decending order

what is a file

collection of data stored by a computer program to be used again

how does bubble sort work

swapping adjacent pairs of values that are compared and swapped

what does linear search help with

check each element of an array in turn for required value

what is a 1D array

list

what is a 2D array

table

what is a primitive data type

variables that can be definded simply by commans built into the programming language

what is also know as an atomic data type

primitive data type

what is an INTEGER

a single whole number

what is a REAL

a single number with a decimal point

what is a CHAR

a single character

what is a STRING

a sequence of zero or more character

what is a BOOLEAN

the logical values TRUE and FALSE

what is a DATE

data consisting of day, month, year

what is an empty string

data of type string with no characters stored in it

what is a structured type

sequence of characters

what kind of data type is a record

user-defined

give an example of an atomic data type

primitive data type

which data type is TECHNICALLY not a primitive data type

string

what are the types of data types

composite, user defined and primitive

what is an atomic data type

basic type of data that cannot be broken down into simpler components

what are features of atomic data types

single value, directly supported in languages, fixed memory blocks

what are the advantaged or atomic data types

efficient, build complex composite types, good for basic computations

what is a user-defined data type

custom data type created to model a specific entity or structure

what does UDT stand for

user-defined data type

what is the structure of a UDT

combination of multiple primitive data types into a single logical unit

what are the features of an UDT

custom structure, abstraction, reusability

what makes UDTs reusable

defined once

where can you use UDTs

complex systems based on real-world entities

what makes primitive data types built-in

directly supported by a programming language

what is the syntax of UDTs

defining using type declarations

benefits of UDTs

readability, reduced redundancy

how do you access a 1D array

loop

how do you access a 2D array

nesteed loop

why do you need to use a nested loop when accessing a 2D array

you need to access columns to be able to access rows

why would declare a record as an array

works when used for several sets of data all part of one particular use

what application (Windows) do we use when making a code for file handling

NotePad

what is a text file

sequence of characters formatted into lines

what happens when you have a code that isn’t saved in a file

lose data when program stops