6.6.2.4. Strings

A string refers to a piece of text. This could be a single character such as "a", or a longer piece of text such as "Hello world". Typically they are entered as being inside either single quotes ' or double quotes ". For example:

s1 = "Hello world"
s2 = 'a'
s3 = "This is a longer piece of text, known as a string."

Note that our style guide means we’ll use double quotes ", but Python at least allows either.

6.6.2.4.1. String literals

A fixed string like the above is known as a string literal. We’re storing only the text we’ve asked for.

6.6.2.4.2. Dynamic strings

Strings can also be built up dynamically. There are lots of different ways of doing this. For example, we might want to store a person’s full name, giving their first name and last name separately. We can do this by concatenating (joining together) two strings. For example in Python

first_name = "Alex"
last_name = "Casson"
full_name = first_name + " " + last_name  # note the space in between the two names

You can also substitute variables into strings. The syntax for this varies between programming languages. In Python, one way of doing this is using f-strings, which we’ll meet in the Labs. A brief example is

age = 21
greeting = f"Hello. My name is {full_name} and I am {age} years old (still)."

6.6.2.4.3. How the computer stores them

How strings are stored in a computer is a little more complex than numbers. We’ve written a separate page about it to give some details.

6.6.2.4.4. Consequences of this storage

Working with strings can be a bit harder than you might expect, particularly with lower level languages such as C/C++ or Rust. There are two core drivers of this:

  • Different text encodings might be used. C, for example pre-dates UTF-8 and so defaults to ASCII. There are libraries that add suitable support for additional characters.

  • We don’t necessarily know how long a string is in advance. There may be different numbers of characters (say in a name), and different characters may need different numbers of types to store them. This makes it harder to allocate memory for strings.

6.6.2.4.5. Working with strings

We’ll work with strings a lot in the Labs and so will gain hands on experience of how they work. There are some other factors to take into account: