choosing data types and how to understand them
I'm working on some small projects and don't fully understand data types and their uses. Here are some things I'm wrestling with.
What data type would I use to represent:
Are there any rock solid resources for data types?
Decimal . DateTime . String . String . float or double . Explanation
Money
The Decimal value type is appropriate for financial calculations requiring large numbers of significant integral and fractional digits and no round-off errors. The Decimal type does not eliminate the need for rounding. Rather, it minimizes errors due to rounding. - MSDN
It also can't be an integer because you'll need a decimal point ($59.9) and integers cannot have one, you'd have to convert it, eg with a cast which will always round it up for you: ((int)7.001) == 8 is true .
You won't use a string either. Text is just the wrong representation (quantifying money does not result in a list of characters, right?). And you'd also like to run some math, I'm sure, and you cannot do that with strings directly because it's not numeric. Eg 2 + 2 = 4 . Try the same with strings: "2" + "2" = "22" ( + is overloaded: it adds for numerics and concatenates for strings).
Edit: My opinion of this has changed! .
Computers and floating points are notoriously complicated and even error-prone (if you do not know precisely what you're doing). I suggest to not use them for money or anything precise & critical.
I recommend to use an integer type that will not overflow (for arbitrary size use BigInteger ) and use it to represent the lowest resolution you need. Eg you're likely to be okay with representing dollars as cents, so 150 is how you would represent 1.5 . Away with rounding errors and scary IEEE standards! woohoo! plus computers are faster with integers so you would typically get better performance, especially if you can manage to use an int , ie you're certain it will not overflow.
Phone Numbers & Security Number
Phone numbers and security numbers are called numbers, but really they're just a string of digits, aren't they? at least that seems the common perception. Well that already tells you: use a string.
You're also unlikely to use a phone number for mathematical operations? (although I do suppose summing up phone numbers would make one wild afternoon).
Birthday
DateTime is the standard .NET type for dates, I'm sure there's no need to explain why, the name is self-explanatory.
Name
String for obvious reasons.
Weight
double or float are used to this kind of things. It depends on how much precision you want. Double gives you more, but the trade-off is that it takes more memory. It only makes a real difference when you have tons of them. My rule of thumb is to go with doubles unless I actually need to use a single/float. That being said, from my experience, almost every game that has something like that (a gravity force value, a weight, and such) is usually a float and rarely a double . Sometimes the domain will give you a different rule of thumb while you're working in it.
Differences between float & double: link & another link.
salary - use float or double; both represent decimal, the latter is double precision which you probably won't need since money usually only goes 2-3 decimal places
DoB - depends on language, most higher level languages have Date or DateTime object types, otherwise you might use a string or char array, or even create your own Date class
name - obviously string or char array
ssn - since is viewed as a string of characters (and also might have non-numeric characters '-') and not necessarily a value of magnitude, you can store this as a string or char array. Same goes for phone#
# of dependents - since can only be a whole number and never a decimal, use integer
weight - again can be represented by a decimal number, so float or double
Think about the values represented for each question.
A salary means money represented by dollars and cents (at least in the US) so you need some sort of decimal / floating type
Date of birth represents a simple date
Name represents a string
Social security number represents a string
Number of dependents for taxes is an integer type as it is a whole number
Weight of earth is again some sort of decimal / floating number
Is this homework? You also did not mention in what type of programming languages but either way these are types and generally consist of strings, dates, numbers, decimals, etc.
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