Unsigned int in C behaves negative

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comparing signed and unsigned int in c

I don't understand why the output of an unsigned int is negative for the following code. Just like a signed int.

  uint32_t yyy=1<<31;
  printf("%d\n",yyy);

The output is:

-2147483648

which is -2^31.

The format specifier for %d expects an int, not an unsigned int, so the code has undefined behaviour. From the C99 standard section 7.19.6.1 The fprintf function:

If any argument is not the correct type for the corresponding conversion specification, the behavior is undefined.

Use %u for unsigned int:

uint32_t yyy=1u<<31;
printf("%u\n",yyy);

Output:

2147483648

C giving negative value to unsigned int when using bitwise , Unsigned int in C behaves negative (8 answers). Closed 6 months ago. I haven't seen this question on here. Basically, my unsigned int is� The assignment of a negative value to an unsigned int does not compute the absolute value of the negative: it interprets as an unsigned int the binary representation of the negative value, i.e., 4294967284 (2^32 - 12). printf("%d") performs the opposite interpretation. This is why your program displays -12.

It's because your printf argument, as %d, is implicitly converting your number to an int.

Use %u instead.

Pitfalls in C and C++: Unsigned types, An int is signed by default, meaning it can represent both positive and negative values. An unsigned is an integer that can never be negative. An ‘unsigned int’ type does not support negative integer value.In this post we will see what is the output if we assign a negative number to ‘unsigned int’ type variable. Link : Difference between signed and unsigned int type Consider the code example given below. 1

Use %u to output unsigned numbers:

printf("%u\n", yyy);

C data types, In the C programming language, data types constitute the semantics and characteristics of The C language provides the four basic arithmetic type specifiers char, int, float and double, and the modifiers signed, unsigned, short, and long. However, changing the type causes the previous code to behave normally: _Bool b� The overflow of unsigned int is fully defined by the c standard community but not defined for the signed int. When we will shift the signed negative value then its results depend on the implementation. The range of unsigned int is larger than the range of the signed int. The modulus operation is almost defined for the unsigned int.

As many have said, use the %u identifier.

The reason for this, is that printf has no way of telling what type any of the extra parameters are (they are given as a va_list), so you the programmer have to provide that information using the format string. When you then provide %d, printf will call this:

int val;
val = va_arg(va_list, int);

and implicitly cast your unsigned int into a signed.

INT13-C. Use bitwise operators only on unsigned , Bitwise operators should be used only with unsigned integer operands, as the ( See INT34-C. Do not shift an expression by a negative number of bits or by� Unsigned integer range. A 1-byte unsigned integer has a range of 0 to 255. Compare this to the 1-byte signed integer range of -128 to 127. Both can store 256 different values, but signed integers use half of their range for negative numbers, whereas unsigned integers can store positive numbers that are twice as large.

Because you are printing it as signed. Use %u instead.

Variables. Data Types. - C++ Tutorials, The same process can be expressed in C++ with the following instruction set: negative values, whereas unsigned types can only represent positive values ( and This is not a fundamental type, but it behaves in a similar way as fundamental� An int type in C, C++, and C# is signed by default. If negative numbers are involved, the int must be signed; an unsigned int cannot represent a negative number.

Vulnerabilities in C : When integers go bad! - Sticky Bits, Vulnerabilities in C : When integers go bad! Unlike int a char is not signed by default; there are actually three different char unsigned short c = 0; however, is sign preserving, i.e. INT_MIN >> 1 will behave as INT_MIN / 2. There are various functions in C which do not return any value or you can say they return void. A function with no return value has the return type as void. For example, void exit (int status); 2: Function arguments as void. There are various functions in C which do not accept any parameter. A function with no parameter can accept a void.

Python convert unsigned to signed integer, It also supports 16-bit unsigned integers, but only for comparison. hex '123' >>> b . Integer used for indexing (same as C ssize_t; normally either int32 or int64) Therefore, when represented on the new system, the negative sign may be present, confuse users expecting NumPy integers to behave similar to Python's int. The negative value is −32767 (not −32768) due to the one's-complement and sign-magnitude representations allowed by the standard, though the two's-complement representation is much more common. %hi: unsigned short unsigned short int: Short unsigned integer type. Contains at least the [0, 65,535] range; %hu: int signed signed int

Unsigned int considered harmful for Java, Input, treat bits as unsigned value int c = a * b; // Output, treat bits as unsigned value. As for the operations that behave differently for signed versus unsigned types, Furthermore, indexing an array with i being negative is also� Therefore, a signed integer can hold both positive and negative numbers (and 0). In this lesson, we’ll focus on signed integers. We’ll discuss unsigned integers (which can only hold non-negative numbers) in the next lesson. Defining signed integers. Here is the preferred way to define the four types of signed integers:

Comments
  • Try printf("%u\n",yyy);
  • Even before you call printf, this code has undefined behavior, if int has 32 bits in your C implementation. The value of 1<<31 overflows an int. You should use 1u<<31, so that it shifts an unsigned int.
  • For portability concerns, one could use the following to print a uint32_t (which may be bigger than an unsigned): 'printf("%"PRIu32"\n", yyy);'
  • I see. Thanks your answer~