24. What is "Hungarian" notation?
Hungarian notation was invented by Charles Simonyi (a Microsoft employee of Hungarian extraction) and presented in his thesis on
meta-programming. Essentially it consists of a naming convention whereby the items named
have information about them encoded in their names - hence "meta-programming".
This allows you to do visual type checking, and eliminates a lot of the up-down
flick reading required in C code to get from variable declaration to variable usage (free
variable declaration in C++ eliminates much of this, but there's all that legacy code to
consider).
Where I part company from Simonyi and MS is the degree to
which he/they use the notation in a problem-domain way rather than a language-domain way.
For instance, take a look at some MS source code : you'll see counter always referred to
with the prefix 'n' (which simply means a counter in pure Hungarian), irrespective of
whether that counter is declared as an int, an unsigned int, a BYTE, whatever. Similarly,
f - meaning flag - may be used to mean a simple BOOL or a UINT array of binary bits. This
allows the underlying type to be re-declared without changing the code (not something you
do very often) but throws away at a stroke the advantages of visual type-checking (I read
code every day).
This is the way I use Hungarian :
<scope
prefix>_<modifier><type><CapitalisedVariableName>
The scope prefix is omitted for local-scope variable. So
for example :
| iCounter |
Integer counter, local scope |
| aiSalesFigures |
An array of integers representing
regional sales figures, at local scope. |
| g_dwLbIndex |
DWORD listbox index, with
app-global scope |
| mg_byOffset |
A BYTE offset with module-global
scope |
| m_byMachineNo |
A class member variable which is
a byte containing a machine number |
| szCustomerName |
A zero-terminated string
containing a customer name, local scope. |
I cannot understand why any professional programmer would
refuse to use Hungarian, but many do. This mystifies me. Take a look at the sources : you
can do it my way, or Microsoft's, I don't care - but I do implore you to use some form of
Hungarian. It will save you a lot of time.
For further information, visit this link :
http://www.csci.csusb.edu/doc/hungarian
