Why long int has a literal modifier, but short int does not?
The question is “why does C# not have this feature?” The answer to that question is always the same. Features are unimplemented by default; C# does not have that feature because no one designed, implemented and shipped the feature to customers.
The absence of a feature does not need justification. Rather, all features must be justified by showing that their benefits outweigh their costs. As the person proposing the feature, the onus is on you to describe why you think the feature is valuable; the onus is not on me to explain why it is not.
Probably there is a strong reason to provide literal modifiers for some types, but not for all. What is it?
Now that is a more answerable question. Now the question is “what justifies the literal suffix on long, and why is that not also a justification for a similar literal suffix on short?”
Integers can be used for a variety of purposes. You can use them as arithmetic numbers. You can use them as collections of bit flags. You can use them as indices into arrays. And there are lots of more special-purpose usages. But I think it is fair to say that most of the time, integers are used as arithmetical numbers.
The vast majority of calculations performed in integers by normal programs involve numbers that are far, far smaller than the range of a 32 bit signed integer — roughly +/- two billion. And lots of modern hardware is extremely efficient when dealing solely with 32 bit integers. It therefore makes sense to make the default representation of numbers to be signed 32 bit integers. C# is therefore designed to make calculations involving 32 bit signed integers look perfectly normal; when you say “x = x + 1” that “1” is understood to be a signed 32 bit integer, and odds are good that x is too, and the result of the sum is too.
What if the calculation is integral but does not fit into the range of a 32 bit integer? “long” 64 bit integers are a sensible next step up; they are also efficient on a lot of hardware and longs have a range that should satisfy the needs of pretty much anyone who isn’t doing heavy-duty combinatorics that involve extremely large numbers. It therefore makes sense to have some way to specify clearly and concisely in source code that this literal here is to be treated as a long integer.
Interop scenarios, or scenarios in which integers are used as bit fields, often require the use of unsigned integers. Again, it makes sense to have a way to clearly and concisely specify that this literal is intended to be treated as an unsigned integer.
So, summing up, when you see “1”, odds are good that the vast majority of the time the user intends it to be used as a 32 bit signed integer. The next most likely cases are that the user intends it to be a long integer or an unsigned int or unsigned long. Therefore there are concise suffixes for each of those cases.
Thus, the feature is justified.
Why is that not a justification for shorts?
Because first, in every context in which a short is legal, it is already legal to use an integer literal. “short x = 1;” is perfectly legal; the compiler realizes that the integer fits into a short and lets you use it.
Second, arithmetic is never done in shorts in C#. Arithmetic can be done in ints, uints, longs and ulongs, but arithmetic is never done in shorts. Shorts promote to int and the arithmetic is done in ints, because like I said before, the vast majority of arithmetic calculations fit into an int. The vast majority do not fit into a short. Short arithmetic is possibly slower on modern hardware which is optimized for ints, and short arithmetic does not take up any less space; it’s going to be done in ints or longs on the chip.
You want a “long” suffix to tell the compiler “this arithmetic needs to be done in longs” but a “short” suffix doesn’t tell the compiler “this arithmetic needs to be done in shorts” because that’s simply not a feature of the C# language to begin with.
The reasons for providing a long suffix and an unsigned syntax do not apply to shorts. If you think there is a compelling benefit to the feature, state what the benefit is. Without a benefit to justify its costs, the feature will not be implemented in C#.