Lecture notes
Computer Science Chapter 12 Notes
- Module
- Computer Science
- Institution
- Cambridge University (CAM)
This is a comprehensive and detailed note on Chapter 12; Data structures for computer science. Essential!!
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CIE IGCSE COMPUTER SCIENCEPractical problem-solving and programming
Chapter 12 – Data structures: arrays and using pre-release material
12.1 Introduction
One of the advantages of using computer systems is their ability to accurately repeat the same task many
times, for example, producing electricity bills or calculating exam scores. In order to do this, programs are
written with loops for repetitions to work with lists of similar items.
These lists are identified by the use of a single name and each item in the list can be found by an index
number showing the place in the list. This type of list is called a one-dimensional array. The items in the list are
the elements of the array.
12.2 Arrays
12.2.1 One-dimensional arrays
In order to use a one-dimensional array in a computer program, consider:
what the array is going to be used for, so it can be given a meaningful name
how many items are going to be stored, so the size of the array can be determined
what sort of data is to be stored, so that the array can be appropriate data type.
For example, if a one-dimensional array for all the students’ test marks in a class was to be set up:
array name StudentMarkTest
number of items = number of students in the class, this could be a constant NoStudents
whole numbers need to be stored, data type Integer.
Arrays usually start at element 0 or element 1. Often if an array starts at element 0, the size of the array is
given as one more than required and element 0 is not used.
1
, Above is array declaration in JavaScript.
Above is declaration of lists and arrays in Python.
12.2.2 Using a variable as an index in an array
In order to repeat the same task many times for all the items in a list, each item needs to be referred to in the
same way using the index number for each element of the one-dimensional array. If a variable is used for this
index number, then the same code can be re-used for each item.
This allows several arrays to be used together with the same index number to show related information, for
example, each student could sit more than one test and the name and gender of the student could also be
recorded.
2
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