String Handling (Cambridge International IGCSE Computer Science)

Spec point — "e) Understand and use the concept of string handling "

String Handling

What is string manipulation?

• String manipulation is the use of programming techniques to modify, analyse or extract information from a string

• Examples of string manipulation include:

  • Case conversion(modify)
  • Length(analyse)
  • Substrings(extract)

Case conversion

• The ability to change a string from one case to another, for example, lower case to upper case

Length

• The ability to count the number of characters in a string, for example, checking a password meets the minimum requirement of 8 characters

Substring

• The ability to extract a sequence of characters from a larger string in order to be used by another function in the program, for example, data validation or combining it with other strings
• Extracting substrings is done by specifying a start position and length in pseudocode, or a start and end index in Python.
• Substring has a start position of 1 in pseudocode and 0 in Python

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]

Answer