String Surgeon
The string operations you can perform in code: finding the length, reading a position, taking a substring, joining strings, and converting between characters, codes and numbers.
Get the method right under pressure
Free interactive practice on the steps that lose marks under exam pressure.
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Cutting and joining text
A string is a piece of text, and programs constantly measure it, cut pieces out of it, and stick pieces together. Knowing the main string operations lets you pull a first name out of a full name, build a message, or check a password length. This module works through length, position, substring, concatenation and conversion.
String words to know
Learn these before you slice and join.
Reading against changing
Some operations just read a string; others make a new one.
Count from zero, name the operation
In the exam, remember the first character sits at position 0, so a string of n characters runs from position 0 to n minus 1. Off-by-one slips here lose marks. Name the operation you need: length to count, position to locate, substring to cut out, concatenation to join, and conversion to turn a string of digits into a number.
Match the operation
- length
- position
- substring
- concatenation
- counts how many characters there are
- finds where a character sits
- takes a part out of a string
- joins strings into one
Match the example
- HELLO has 5 characters
- H sits at position 0
- taking ELL from HELLO
- joining cat and fish into catfish
- this is finding the length
- this is reading a position
- this is taking a substring
- this is concatenation
Where is the first character?
In the string HELLO, at which position is the first character, the H?
- Position 0
- Position 1
- Position 5
- It has no position
True about strings
Select the TWO true statements about string operations.
- Length gives the number of characters
- Concatenation joins strings together
- A substring must be the whole string
- The first character is at position 1
Length of the join
The string cat has 3 characters and the string fish has 4 characters. When they are joined together, add the two lengths to find how many characters the result has. What is the answer?
Order the name-splitter
Put the steps of pulling a first name out of a full name in order, earliest first.
- Find the position of the space
- Take the substring before it
- Store that as the first name
- Use it in a greeting
Complete the rules
The _____ of a string is how many characters it has. The first character sits at position _____. Taking a part of a string is called a _____, and joining strings together is called _____.
Spot the new-string operations
Tap the TWO operations that produce a brand new string rather than just reading one.
- taking a substring
- concatenating two strings
- finding the length
- reading a position
Pick the operation
Read each task and choose the string operation needed.
- You need to check that a password has at least 8 characters. Which operation do you use?
- You want to join a first name and a surname into one full name. Which operation do you use?
- You need just the year part from a date written as text. Which operation do you use?
Explain string operations
Explain the main string operations and how positions in a string are numbered.
- Say what length and position each do
- Explain the difference between a substring and concatenation
- State where the first character sits and why off-by-one errors happen