Beginning variable names with the prefix 'the'

Question

Okay, this one is pretty hard to google.

Occasionally, I stumble upon code in any language that uses a naming convention where variable names start with the prefix 'the' under certain circumstances.

I could not figure out, however, what these circumstances are. So my questions are:

1. Is this convention common? Does it have a name?

2. If 1) is still "ungoogleable": What are the principles behind this convention? What problems does it address? I would like to understand.

3. If not covered by 1) and 2): Where does the convention come from? What are its origins? Is or was it connected to a specific programming language?

Examples:

• From the Steinberg ASIO SDK 2.3, file asiodrivers.cpp, line 88:

  extern IASIO* theAsioDriver;
  

  where IASIO is an interface definition.

• http://hl7api.sourceforge.net/base/apidocs/src-html/ca/uhn/hl7v2/util/StringUtil.html

• http://xml.apache.org/xalan-c/apiDocs/classXStringAllocator.html

• http://www.cplusplus.com/forum/beginner/65050/

• http://www.cise.ufl.edu/~sahni/dsaac/enrich/c20/fold2.htm

I am hoping for some insight into why people do this. One example might be to tell parameters from members in setter/getter methods, but this choice of prefix seems random to me.

Answer 1

The only time I would be tempted to start a variable name with the would be to indicate that it is a singleton. Other than that its use seems unnecessary.