Terminology – What Are the Different Meanings of ‘Fixture’?

• subprogram, subroutine
  "subroutine" probably comes from assembly language. Some processors include instructions to support subroutines as a way of organizing code and reusing common sections of code. For example, the 6502 processor had JSR (jump to subroutine) and RTS (return from subroutine) instructions. I remember it also being used a lot in structured programming, in which a program is a hierarchy of units of code which were sometimes called subroutines or subprograms. IMO, these are the most generic terms for some unit of code to which control is temporarily transferred for the purpose of completing a given task.

• function, procedure
  These are often used interchangeably, but in some languages there's a distinction. In Pascal, a function is a subprogram that returns a value, while a procedure is a subprogram that doesn't. In C and related languages, every subprogram has a return type (even if it's void), so there's no distinction.

• method, member function
  These are two names for the same thing -- essentially a function that's associated with a given class or object.

• operator
  Every language has a set of built-in operators. In some languages, such as C++, operators are functions that can be overridden (i.e. replaced) and/or overloaded (i.e. defined for new types).

• anonymous function
  This refers to a function without a name. Anonymous functions are essentially blocks of code that can be assigned to variables or passed as parameters for subsequent use, for example as a completion routine.

• closure, lambda expression, block
  A closure is a chunk of code that's bound to a set of variables. I think of closures as anonymous functions plus context.

The generic definition of "data structure" is anything that can hold your data in a structured way, so yes this would include composite types and primitive types in addition to abstract data types. For example, a string is a data structure as it can hold a sequence of characters in a structured way.

However, the term also has another meaning to programmers.

Since the term "data structures" is so broad, developers usually use a more specific term to identify what they are talking about, such as class or data object or primitive type, and the specific term used for most complex or abstract data types is "data structure"

This is why you hear "data structure" most frequently being used for abstract data types like Arrays, Lists, Trees and Hashtables, and not for things like primitive data types