Hungarian notation is a scheme used in lanquages such as C that do not enforce string type checking. See Programming Windows by Petzold for details on where the name hungarian came from.

Prepend the letter to the variable. For instance achName or dblSalary. This makes the mistake of "achName += dblSalary;" more noticeable when proofing the code. It's not as necessary with languages like C++ whose type checking is strictly enforced.

a	Array(compound type)
ach	Array of char (use sz)
b	Boolean
btn	TButton
cb	count of bytes
ch	character
cr	color (COLORREF)
dbl	double
ds	DString 
dw	Unsigned long, (WINDOWS.H typedef: DWORD)
f	float
hdc	Handle to a device context
hwnd	Handle to a window
i	Index(compound)
l	long integer
lp	long (or far) pointer (compound type)
n	integer
np	Near pointer
pb	Pointer to a transfer buffer
pf	pointer to a function

pt	An x,y point (WINDOWS.H typedef: POINT
r	A rectangle structure (WINDOWS.H typedef: RECT)
st	TStatic
sz	null terminated string
w	Unsigned integer (WH typedef: WORD)