Flashcards · 9618 · AS Topic 10

Data Types and Structures (AS Level) flashcards

18 cards on AS Topic 10, subtopics 10.1 to 10.4. Pick a subtopic or study them all.

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Which basic data types does 9618 pseudocode use?: INTEGER, REAL, CHAR, STRING, BOOLEAN and DATE.
How do you declare a variable and a constant in 9618 pseudocode?: DECLARE Total : INTEGER CONSTANT VAT = 0.2 A constant’s value is fixed when it is declared and cannot be changed by the program.
What is a record data type?: A composite data type made of several fields, which can be of different data types, describing one item (such as one student).
How do you define a record type in 9618 pseudocode?: TYPE TStudent DECLARE Name : STRING DECLARE Age : INTEGER ENDTYPE Then DECLARE Pupil : TStudent and use dot notation: Pupil.Name ← "Ali"

What is an array?: A fixed-size data structure holding elements of the same data type under one identifier, each reached by its index.
How do you declare 1D and 2D arrays in 9618 pseudocode?: DECLARE Names : ARRAY[1:30] OF STRING DECLARE Grid : ARRAY[1:3, 1:5] OF INTEGER The bounds give the lower and upper index of each dimension.
How does a linear search work?: Check each element in turn from the start until the item is found or the end of the array is reached. The data need not be sorted.
How does a bubble sort work?: Compare each pair of adjacent elements and swap them if they are in the wrong order. Repeat passes until a pass makes no swaps.
How can a bubble sort be made more efficient?: Use a flag to stop as soon as a pass makes no swaps, and reduce the number of comparisons by one after each pass, since the largest value is already in place.

Why are files needed?: Data in variables is lost when a program ends. A file stores data permanently, so it can be read back by the program later or by other programs.
What are the three file modes for a text file in 9618 pseudocode?: READ, WRITE and APPEND, e.g. OPENFILE "Scores.txt" FOR READ. WRITE replaces any existing contents; APPEND adds to the end.
How do you read every line of a text file in 9618 pseudocode?: OPENFILE "Data.txt" FOR READ WHILE NOT EOF("Data.txt") READFILE "Data.txt", Line … ENDWHILE CLOSEFILE "Data.txt"
How do you write a line to a text file in 9618 pseudocode?: OPENFILE "Log.txt" FOR WRITE (or FOR APPEND) WRITEFILE "Log.txt", Line CLOSEFILE "Log.txt"

What is an abstract data type (ADT)?: A collection of data together with a set of operations on that data, defined by what it does rather than how it is implemented.
How does a stack work?: Last in, first out (LIFO). Items are pushed onto and popped off the top. A top-of-stack pointer tracks the last item.
How does a queue work?: First in, first out (FIFO). Items join at the rear (enqueue) and leave from the front (dequeue), tracked by front and rear pointers. A circular queue reuses freed spaces.
What is a linked list?: A list of nodes, each holding data and a pointer to the next node. A start pointer gives the first node and a null pointer marks the end. Items can be inserted or deleted by changing pointers, without moving data.
How can a stack, queue or linked list be implemented using arrays?: Store the items in a 1D array and keep integer pointers (indices) for the top, front/rear or next node. A linked list also keeps a free list of unused array positions.