String Handling (Cambridge (CIE) IGCSE Computer Science): Revision Note

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

Name ← "Sarah"
OUTPUT UCASE(Name)

Name = "Sarah"
print(Name.upper())

Name ← "SARAH"
OUTPUT LCASE(Name)

Name = "SARAH"
print(Name.lower())

Length

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

Password ← "letmein"
OUTPUT LENGTH(Password)

Password = "letmein"
print(len(Password))

Password ← "letmein"
IF LENGTH(Password) >= 8
    THEN
        OUTPUT "Password accepted"
    ELSE
        OUTPUT "Password too short"
ENDIF

Password = "letmein"
if len(Password) >= 8:
    print("Password accepted")
else:
    print("Password too short")

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

Word ← "Revision"
OUTPUT SUBSTRING(Word, 1, 3)

Word = "Revision"
print(Word[0:2])

Word ← "Revision"
OUTPUT SUBSTRING(Word, 3, 6)

Word = "Revision" 
print(Word[2:5])