How do you set, clear and toggle a single bit in C/C++?

Setting a bitUse the bitwise OR operator (|) to set a bit.number |= 1 << x;That will set bit x.Clearing a bitUse the bitwise AND operator (&) to clear a bit.number &= ~(1 << x);That will clear bit x. You must invert the bit string with the bitwise NOT operator (~), then AND it.Toggling a bitThe XOR operator (^) can be used to toggle a bit.number ^= 1 << x;That will toggle bit x.Checking a bitYou didn't ask for this but I might as well add it.To check a bit, AND it with the bit you want to check:bit = number...

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Why does printf not flush after the call unless a newline is in the format string?

The stdout stream is buffered, so will only display what's in the buffer after it reaches a newline (or when it's told to). You have a few options to print immediately:Print to stderr instead using fprintf:fprintf(stderr, "I will be printed immediately");Flush stdout whenever you need it to using fflush:printf("Buffered, will be flushed");fflush(stdout); // Will now print everything in the stdout bufferEdit: From Andy Ross's comment below, you can also disable buffering on stdout by using setbuf:setbuf(stdout, NUL...

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Best way to detect integer overflow in C/C++

There is a way to determine whether an operation is likely to overflow, using the positions of the most-significant one-bits in the operands and a little basic binary-math knowledge.For addition, any two operands will result in (at most) one bit more than the largest operand's highest one-bit. For example:bool addition_is_safe(uint32_t a, uint32_t b) { size_t a_bits=highestOneBitPosition(a), b_bits=highestOneBitPosition(b); return (a_bits<32 && b_bits<32);}For multiplication, any two operands will result in (at most)...

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what is array decaying?

It's said that arrays "decay" into pointers. A C++ array declared as int numbers[5] cannot be re-pointed, i.e. you can't say numbers = 0x5a5aff23.When you pass an array into a function, either directly or with an explicit pointer to that array, it has decayed functionality, in that you lose the ability to call sizeof() on that item, because it essentially becomes a pointer. This is why it's preferred to pass by reference (among other reasons).Three ways to pass in an array:void by_value(const T array[])void by_pointer(const T* const array)void...

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Can you write object oriented code in C?

Since you're talking about polymorphism then yes, you can, we were doing that sort of stuff years before C++ came about.Basically you use a struct to hold both the data and a list of function pointers to point to the relevant functions for that data.So, in a communications class, you would have an open, read, write and close call which would be maintained as four function pointers in the structure, alongside the data for an object, something like:typedef struct { int (*open)(void *self, char *fspec); int (*close)(void *self); ...

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