String Handling

Strings are a sequence of characters, such as letters, numbers, and symbols
They are used to represent text in a computer program
String handling refers to the various operations that can be performed on strings

Length

The length of a string is the number of characters it contains
In Python, the len() function is used to find the length of a string
In Java, the length() method is used to find the length of a string
In Visual Basic, the Len() function is used to find the length of a string

Substring

A substring is a portion of a string
In Python, the substring can be obtained using the slicing operator [:]
In Java, the substring() method is used to obtain a substring
In Visual Basic, the Mid() function is used to obtain a substring

Upper

The upper() method converts all characters of a string to uppercase
In Python, the upper() method is used to convert a string to uppercase
In Java, the toUpperCase() method is used to convert a string to uppercase
In Visual Basic, the UCase() function is used to convert a string to uppercase

Lower

The lower() method converts all characters of a string to lowercase
In Python, the lower() method is used to convert a string to lowercase
In Java, the toLowerCase() method is used to convert a string to lowercase
In Visual Basic, the LCase() function is used to convert a string to lowercase

Pseudocode example:

string phrase ← "Save my exams"

length ← LENGTH(phrase)

substring ← SUBSTRING(phrase, 5, 2)

upper ← TO_UPPER(phrase)

lower ← TO_LOWER(phrase)

Python example:

phrase = "Save my exams"

length = len(phrase)

substring = phrase[4:6]

upper = phrase.upper()

lower = phrase.lower()

Java example:

String phrase = "Save my exams";

int length = phrase.length();

String substring = phrase.substring(4, 6);

String upper = phrase.toUpperCase();

String lower = phrase.toLowerCase();

Visual basic example:

Dim phrase As String = "Save my exams"

Dim length As Integer = phrase.Length

Dim substring As String = phrase.Substring(4, 2)

Dim upper As String = phrase.ToUpper()

Dim lower As String = phrase.ToLower()

Position of First Character

The first character of a string can be at position zero or one, depending on the programming language
In Python and Java, the first character of a string is at position zero
In Visual Basic, the first character of a string is at position one

Worked example

The function Length(x) finds the length of a string x. The function substring(x,y,z) finds a substring of x starting at position y and z characters long. The first character in x is in position 1.

Write pseudocode statements to:

Store the string “Save my exams” in x
Find the length of the string and output it
Extract the word exams from the string and output it

[6]

	`X` ← `"Save my exams"`	[1] for storing string in X.
	`OUTPUT Length(X)`	[1] for calling the function length. [1] for using the correct parameter X.
	`Y` ← `9` `Z` ← `5`
	`OUTPUT SubString(X,Y,Z)`	[1] for using the substring function. [1] for correct parameters. [1] for outputting length and substring return values.

Exam Tip

Remember that the length of a string is not the same as the index of the last character in the string
Be careful when counting positions in a string, as the first character can be at position zero or one depending on the programming language

String Handling (CIE IGCSE Computer Science)

Revision Note