4.1.2
Arrays & Strings
Arrays
Arrays
Arrays are really useful when you have access to large amounts of related data, but you don't want to store in multiple variables.
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Arrays
Arrays
- An array is a data structure that stores a fixed number of values under a single identifier.
- The values must be of the same type.
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Array elements
Array elements
- Each piece of data inside an array is called an element.
- Each element has an index, which is its position within the array.
- We start counting the indices from 0.
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Arrays in pseudocode
Arrays in pseudocode
- An array of ten items can be created using the following syntax:
- array name_of_array[10]
- Values can be assigned as follows:
- name_of_array[0] = "Hello"
- Values can be accessed as follows:
- print(name_of_array[0])
2D Arrays
2D Arrays
A 2D array is the data structure which consists of an array of arrays.
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2D Array
2D Array
- A 2D array is a data structure where arrays are filled with other arrays.
- This can be used to represent a 2D surface, or records.
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Accessing elements
Accessing elements
- To access an individual array, we can access the array as usual:
- array = my2DArray[4]
- To access an individual element, we use this syntax:
- array[5][0]
- This would get the first element of the sixth array.
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Applications of 2D arrays
Applications of 2D arrays
- 2D arrays are often used to represent a 2D surface, for example a chess board:
- Each element of the 2D array could contain the chess piece in that location.
- 2D arrays can be used to represent a database:
- The outer array stores a collection of records.
- The inner arrays store a single record.
Strings
Strings
Strings are special cases of arrays or lists, where each element is a character. There are many methods we can apply to them:
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Concatenation
Concatenation
- Concatenation is joining two strings together.
- This can be done with the + sign. E.g:
- "Hello " + "World" = "Hello World".
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Accessing a character
Accessing a character
- Remember, strings are just lists. So we can access a specific character in the exact same way as we access a list element:
- string[3] would get the fourth character.
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Length of a string
Length of a string
- The length of a string is given by the len function:
- len("Hello") would give 5.
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Substrings
Substrings
- A substring is a part of a longer string.
- In pseudocode, we use the function:
- stringname.subString(startPos, numberOfChars)
- This takes a substring starting at the 'startPos'th character, and takes the stated number of characters.
1Components of a Computer
1.1Structure & Function of the Processor
1.2Types of Processors
2Software & Software Development
2.1Systems Software
2.2Applications Generation
2.3Software Development
3Exchanging Data
3.1Compression, Encryption & Hashing
3.3Networks
4Data Types, Data Structures & Algorithms
4.1Data Types
5Legal, Moral, Cultural & Ethical Issues
5.1Computing Related Legislation
6Elements of Computational Thinking
6.1Thinking Abstractly
6.2Thinking Procedurally
6.3Thinking Logically
7Problem Solving & Programming
7.1Programming Techniques
7.2Programming Construction
Jump to other topics
1Components of a Computer
1.1Structure & Function of the Processor
1.2Types of Processors
2Software & Software Development
2.1Systems Software
2.2Applications Generation
2.3Software Development
3Exchanging Data
3.1Compression, Encryption & Hashing
3.3Networks
4Data Types, Data Structures & Algorithms
4.1Data Types
5Legal, Moral, Cultural & Ethical Issues
5.1Computing Related Legislation
6Elements of Computational Thinking
6.1Thinking Abstractly
6.2Thinking Procedurally
6.3Thinking Logically
7Problem Solving & Programming
7.1Programming Techniques
7.2Programming Construction
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