VCE Applied Computing: Software Development

A **data type** says what kind of value a variable holds and so which operations make sense on it. A program stores a person's name, their age, the price of an item, whether they are logged in and the day they enrolled in quite different ways, and choosing the right type for each one is the first design decision made about any piece of data. Most languages check types (or convert between them) whenever a value is assigned or used in an expression, which is why a wrong choice shows up later as a wrong answer or a crash. The types a program commonly needs are text, numeric, date/time and Boolean. ## Text A **character** is a single symbol: a letter, digit, punctuation mark or space. A **string** is a sequence of characters, such as a name, an address or a postcode. Strings are the right type for anything that is identified by its symbols rather than calculated with, and that includes values made of digits. A phone number, a postcode or a student ID should be stored as a string. Nobody adds two phone numbers together, and a number type would drop the leading zero from 0412 345 678, because an integer has no way of recording a leading zero. A string also keeps the spaces and the plus sign in +61 3 9123 4567. Common string operations are concatenation (joining two strings), finding the length, extracting part of a string (a substring), changing case and comparing two strings. ```python first = "Mia" last = "Chen" full_name = first + " " + last # "Mia Chen" print(len(full_name))…