# 12 Data Structure

Nov 10, 2019

Hello SCIE programmers, this is Jack.This article sheds light on the basic data structure in IGCSE.

## 12.1 Overall of data structure

Data structure is a way to store information in computers.There are generally four types of data structure:

### SET

In IGCSE, we only talk about one kind of structure in linear structure. That is array.

## 12.2 What is an array

Array can be understood as a kind of table.It is similar to the concept of series in math.For example, in math we can record a series as aiai​, where a1a1​ means the first element in the series aa.Whilst in programming, it can be written as a[i]a[i].
In conclude, an array is made up of its identifier(aa) and its index (ii).

## 12.3 How to declare an array

We can use
`DECLARE : ARRAY[] OF`
to declare an array.
For example, we want to have an array that can store 50 students id number.
`DECLARE StudentId: ARRAY[50] OF INTEGER`
Another example, we want to have an array that can store 50 students’ name.
`DECLARE StudentName: ARRAY[50] OF STRING`
And another example, we want to have an array that can store whether 50 students passed the exam or not.
`DECLARE StudentPassed: ARRAY[50] OF BOOLEAN`

### NOTE:

Be careful of the datatype when declaring an array.

## 12.4 How to use an array

### 12.4.1 ASSIGN VALUES TO AN ARRAY

Let’s say you have an array called Name.
`DECLARE Name: ARRAY[50] OF STRING`
The whole array can be seen as:

123……50
‘ ‘‘ ‘‘ ‘‘ ‘

(‘ ‘ means empty)
You want the first element in the array to be your name.
You can just do:

#### Jack Tang

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