Data type

Programming languages have several primitive data types to store and represent data. Types define the set of values a variable of type $T$ can take. Languages can be divided into several categories:

• Strongly/weakly typed
  • Weakly-typed languages convert between unrelated types implicitly.
  • Strongly-typed languages don’t allow implicit conversions.
• Statically/dynamically typed
  • Statically-typed languages do type checking (verifying/enforcing constraints) at compile-time.
  • Dynamically-typed languages do this at runtime.

Type systems

Common types

A brief list of common types in programming languages:

• Integers
  • int, 32 bits
  • short, 16 bits
  • long, $\ge$ 32 bits
  • long long, 64 bits
• Floating-point number
  • float, 32 bits, 7 digit precision
  • double, 64 bits, 15 digit precision (“double precision”)
  • long double, 19 digit precision
• Text
  • char, 8 bits, in single quotes
  • string, for a size-varying string, in double quotes
• Boolean values, bool (true, false)
• And the void type

Note that the exact bit/byte length for a type will vary from machine to machine. Often some types are defined such that we can use a certain bit length, i.e., int8_t (or i8) for an 8-int signed integer.

Variant types

A composite data type is constructed with multiple primitive data types (listed above). In C/C++/Rust, composite types are implemented with the struct keyword.

Sub-pages

• Type annotation