Thread: Help with understanding ( int, char, long, short, signed, unsigned etc.... )

Most of you will answer this question with "Go read a book" or "Don't you own a c/c++ book?"

k. The question is simple: When should I use a long, int, char, unsigned/signed variables?? K, thas very blunt, but this should narrow it down...

When I declare a variable "unsigned;" what did I do it???
Why would I delcare an integer "long" or "short" ( unsigned or signed)??

Any examples of when things like "unsigned", "long", "short" etc... should, and shouldn't be used???



One more thing; I noticed a lot of the code I see IN MSVC++ has variables with these "pre-fixes", for instance "Cdialog" (notice the C in front of the word Dialog) or "nResponse" ( notice the 'n' in front of Response ), or things like m_nResponse (notice the "m_n" in front of the word "Response") are these prefixes suppposed to represent things?

I know these may seem like stupid questions, i have been programming for awhile.. theses are just things that I comme across at time.

Help will be appreciated.

Try Google.

Just kidding, you asked the question nicely.

Declaring the variable unsigned means that instead of having a range from, for example, -127 to 128, it has a range that goes from 0 to 256. You can't have negative numbers with an unsigned variable, but you can with a signed one. So...depends on what you need.

As a general rule of thumb, figure out what the maximum and minimum values for the variable will be, and then pick the smallest variable (in byte size) that you can use for that range. If you're using floats/doubles, decide how much precision you need as well.

Code:

Type     Meaning
-----------------
char	character
int	integer
float	single-precision floating point
double	double-precision floating point

Code:

    Typical Sizes
Type		Size
---------------------------
char  		 8 bits
short int 	 8 or 16 bits
int 		16 or 32 bits
long int 	32 bits
float 		32 bits
double 		64 bits
long double 	80 bits

edit: Those things before the variable names are known as Hungarian notation, and for more info on that one, I will direct you to Google.

Is it really necessary to find the best variable for whatever your purpose is? I mean at the level I'm at it probably isn't, but does it ever become a real necessity?

>>> but does it ever become a real necessity?

Of course. Assuming you use only unsigned, if you have declared 2 variables that are 8bits wide, and try to add them together and store the result in another 8bit variable, and the result is greater than 255 what result will you get?

Would you want the same programmer working out your pay or tax?

When making programs you need to represent the 'objects' in it in different ways, like ages with integers, names with a series of characters, prices with floating point numbers etc...
So why are there so many sizes of the 'same type' like short, int & long you ask? Well, you could make one universal size of say 256 bytes for every type to make it fit every (read: most) possible situation, but with variables that big memory would be consumed fast and calculations would be slow. So if you don't need to represent large numbers (ie just 1 - 10) you should just use a short, or even a char. But if you need to know the amount of milliseconds since a certain date 1970 you need to use a larger variable, ie a long (actually, long is a modifier to an int so it's long int but compilers usually (always?) understands if you type just long).