Lære AND, OR, XOR, and NOT Operators | Bitwise Operators and Shifts

Bitwise operators are essential tools in C for directly manipulating the individual bits of integer values. The four fundamental bitwise operators are AND (&), OR (|), XOR (^), and NOT (~). Each operator works at the bit level, applying its logic to corresponding bits in the operands. Understanding these operators begins with their truth tables, which describe how each operator combines or transforms bits:

Bitwise AND (`&`)

Produces a 1 only if both bits are 1; otherwise, the result is 0.

Bitwise OR (`|`)

Produces a 1 if either bit is 1; the result is 0 only if both bits are 0.

Bitwise XOR (`^`)

Produces a 1 if the bits are different; if they are the same, the result is 0.

Bitwise NOT (`~`)

Flips every bit: 1 becomes 0, and 0 becomes 1.

Here are the truth tables for the three binary operators:

For the unary NOT operator:

These operators allow you to set, clear, toggle, and test individual bits within integer values, which is a powerful technique for low-level programming and hardware control.

main.c


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#include <stdio.h>

// Helper function to print an integer in binary (8 bits)
void print_binary(unsigned int n) {
    for (int i = 7; i >= 0; i--) {
        printf("%u", (n >> i) & 1);
    }
}

int main() {
    unsigned int a = 42; // 00101010
    unsigned int b = 15; // 00001111

    printf("a      = %3u (", a);
    print_binary(a);
    printf(")\n");

    printf("b      = %3u (", b);
    print_binary(b);
    printf(")\n");

    printf("a & b  = %3u (", a & b);
    print_binary(a & b);
    printf(")  // AND\n");

    printf("a | b  = %3u (", a | b);
    print_binary(a | b);
    printf(")  // OR\n");

    printf("a ^ b  = %3u (", a ^ b);
    print_binary(a ^ b);
    printf(")  // XOR\n");

    printf("~a     = %3u (", (unsigned int)(~a & 0xFF));
    print_binary(~a & 0xFF);
    printf(")  // NOT (showing only 8 bits)\n");

    return 0;
}

Bitwise operators are used when you need precise control over binary data. By observing the program output, you can see how each operator changes the bits of integers a and b. The AND operator (a & b) is commonly used to mask bits and check specific flags, while the OR operator (a | b) is used to set bits and enable features.

The XOR operator (a ^ b) helps toggle bits or detect differences between values, and the NOT operator (~a) inverts all bits to create masks or perform bitwise negation. Together, these operators are the basis for techniques like flag management, bit masking, and efficient data representation.

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