Boolean Flags with Bits
When you want to keep track of several independent on/off states—such as options, features, or permissions—in a C program, you can use individual bits within an integer as boolean flags. Each bit in a variable can represent a single true/false condition, letting you store and manipulate many flags using just one value. This approach is far more memory-efficient than declaring a separate variable for every state, especially when you only need to know whether each state is enabled or disabled.
flags.c
1234567891011121314151617181920212223242526272829303132333435363738#include <stdio.h> // Define flag positions using bit shifting #define FLAG_READ (1 << 0) // 0001 #define FLAG_WRITE (1 << 1) // 0010 #define FLAG_EXEC (1 << 2) // 0100 #define FLAG_HIDDEN (1 << 3) // 1000 int main() { unsigned char file_flags = 0; // All flags are off // Enable READ and EXEC flags file_flags |= FLAG_READ; file_flags |= FLAG_EXEC; printf("Flags after enabling READ and EXEC: %02X\n", file_flags); // Check if WRITE flag is enabled if (file_flags & FLAG_WRITE) { printf("WRITE flag is enabled.\n"); } else { printf("WRITE flag is disabled.\n"); } // Enable WRITE flag file_flags |= FLAG_WRITE; printf("Flags after enabling WRITE: %02X\n", file_flags); // Disable EXEC flag file_flags &= ~FLAG_EXEC; printf("Flags after disabling EXEC: %02X\n", file_flags); // Toggle HIDDEN flag file_flags ^= FLAG_HIDDEN; printf("Flags after toggling HIDDEN: %02X\n", file_flags); return 0; }
Using bitwise flags offers several advantages over using separate variables for each boolean state. You can represent many flags in just one variable, reducing memory usage and simplifying data structures. Bitwise operations for setting, clearing, and checking flags are fast and can be performed in a single instruction. This makes your code more efficient and scalable, especially when you need to handle many independent options.
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When you want to keep track of several independent on/off states—such as options, features, or permissions—in a C program, you can use individual bits within an integer as boolean flags. Each bit in a variable can represent a single true/false condition, letting you store and manipulate many flags using just one value. This approach is far more memory-efficient than declaring a separate variable for every state, especially when you only need to know whether each state is enabled or disabled.
flags.c
1234567891011121314151617181920212223242526272829303132333435363738#include <stdio.h> // Define flag positions using bit shifting #define FLAG_READ (1 << 0) // 0001 #define FLAG_WRITE (1 << 1) // 0010 #define FLAG_EXEC (1 << 2) // 0100 #define FLAG_HIDDEN (1 << 3) // 1000 int main() { unsigned char file_flags = 0; // All flags are off // Enable READ and EXEC flags file_flags |= FLAG_READ; file_flags |= FLAG_EXEC; printf("Flags after enabling READ and EXEC: %02X\n", file_flags); // Check if WRITE flag is enabled if (file_flags & FLAG_WRITE) { printf("WRITE flag is enabled.\n"); } else { printf("WRITE flag is disabled.\n"); } // Enable WRITE flag file_flags |= FLAG_WRITE; printf("Flags after enabling WRITE: %02X\n", file_flags); // Disable EXEC flag file_flags &= ~FLAG_EXEC; printf("Flags after disabling EXEC: %02X\n", file_flags); // Toggle HIDDEN flag file_flags ^= FLAG_HIDDEN; printf("Flags after toggling HIDDEN: %02X\n", file_flags); return 0; }
Using bitwise flags offers several advantages over using separate variables for each boolean state. You can represent many flags in just one variable, reducing memory usage and simplifying data structures. Bitwise operations for setting, clearing, and checking flags are fast and can be performed in a single instruction. This makes your code more efficient and scalable, especially when you need to handle many independent options.
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