18,446,744,073,709,551,615 This number mentioned, 18,446,744,073,709,551,615, is actually 2^64 − 1. The important thing here is that 2^64-1 is essentially 0-based 2^64. The first digit of an unsigned integer is 0, not 1. So if the maximum value is 1, it has two possible values: 0, or 1 (2). Let’s look at 2^64 – 1 in … Read more
In Windows Vista and Windows 7 there a new utility for handling drivers setup call PnPUtil. It handles exactly this kind of work. Just copy all your driver relevant files(*.inf, *.cat, *.sys) to a directory on the target computer and use PnPUtil -i -a <InfName>.inf Note: You will need to be in an administrator context … Read more
When comparing signed with unsigned, the compiler converts the signed value to unsigned. For equality, this doesn’t matter, -1 == (unsigned) -1. For other comparisons it matters, e.g. the following is true: -1 > 2U. EDIT: References: 5/9: (Expressions) Many binary operators that expect operands of arithmetic or enumeration type cause conversions and yield result … Read more
It won’t make a difference for strings. But in C you can use a char to do math, when it will make a difference. In fact, when working in constrained memory environments, like embedded 8 bit applications a char will often be used to do math, and then it makes a big difference. This is … Read more
The draft C++ standard has the following footnote 296 in section 27.5.2 Types which says: streamsize is used in most places where ISO C would use size_t. Most of the uses of streamsize could use size_t, except for the strstreambuf constructors, which require negative values. It should probably be the signed type corresponding to size_t … Read more
The number itself is always interpreted as a non-negative number. Hexadecimal constants don’t have a sign or any inherent way to express a negative number. The type of the constant is the first one of these which can represent their value: int unsigned int long int unsigned long int long long int unsigned long long … Read more
There are three distinct basic character types: char, signed char and unsigned char. Although there are three character types, there are only two representations: signed and unsigned. The (plain)char uses one of these representations. Which of the other two character representations is equivalent to char depends on the compiler. In an unsigned type, all the … Read more
import ctypes number = lv & 0xFFFFFFFF signed_number = ctypes.c_long(number).value
Your question is genuinely intriguing as the unsigned version consistently produces code that is 10 to 20% slower. Yet there are multiple problems in the code: Both functions return 0 for 2, 3, 5 and 7, which is incorrect. The test if (i != num) return 0; else return 1; is completely useless as the … Read more
An enum is guaranteed to be represented by an integer, but the actual type (and its signedness) is implementation-dependent. You can force an enumeration to be represented by a signed type by giving one of the enumerators a negative value: enum SignedEnum { a = -1 }; In C++0x, the underlying type of an enumeration … Read more