// Some fancy bit manipulation examples. // Notes: // - Using statement is frowned upon by professional // programmers, which is why you won't see it here. // - Nibbles are 4 bits in size so 2 of them make a // byte. // - Bytes are 8 bits in size so 4 of them make an int. // - Hexadecimal numbers are specified with 0x10. The // leading 0 tells the compiler a number begins. The // x specifies the number is in hex. Followed by the // number 16 in this example. Each digit in a hex // number is a nibble containing the values 0 to 15. // 0 to 9 is used for those values. a to f is used // for 10 to 15. // - Binary numbers use b to specify binary and 0 or // 1 is used to specify bits. I've used the _ to // separate the nibbles to make hex to binary // conversion easier to perform. #include #include int main() { // Original number to play with. unsigned int original = 0x87654321; std::cout << "Binary manipulation of decimal " << original << " hex " << std::hex << original << " binary" << std::endl << std::bitset<32>(original) << std::endl; // Grab byte 3 (0x32). unsigned int result = (original&0xff00)>>8; std::cout << std::hex << "3rd byte is " << result << std::endl; // Swap 1st and 4th bytes. result = ((original&0xff000000)>>24)+ ((original&0xff)<<24)+(original&0xffff00); std::cout << std::hex << "1st & 4th swapped is " << result << std::endl; // Reverse the nibbles. unsigned int temporary = original; result = 0; for (int i = 0; i < 8; i++) { result <<= 4; result += temporary&0xf; temporary >>= 4; } std::cout << std::hex << "Reversed nibbles is " << result << std::endl; // Reverse the bits ( // 0b1000_0111_0110_0101_0100_0011_0010_0001 to // 0b1000_0100_1100_0010_1010_0110_1110_0001 or // 0x84c2a6e1). temporary = original; result = 0; for (int i = 0; i < 32; i++) { result <<= 1; result += temporary&0x1; temporary >>= 1; } std::cout << std::hex << "Reversed bits is " << result << std::endl << std::bitset<32>(result) << std::endl; // BCD unsigned char bcd1[10]; temporary = original; for (int i = 9; i >= 0; i--) { bcd1[i] = temporary%10; temporary /= 10; } std::cout << "BCD array is"; for (int i = 0; i < 10; i++) std::cout << " " << (int)bcd1[i]; std::cout << std::endl; // BCD 8 bit version int unsigned long long bcd2 = 0; unsigned int value = 12345678; temporary = value; for (unsigned int i = 10000000; i > 0; i /= 10) { bcd2 = (bcd2<<8)+temporary/i; temporary %= i; } std::cout.copyfmt(std::ios(NULL)); std::cout << "BCD 8bit int is " << value << "=" << std::hex << bcd2 << std::endl; // BCD 4 bit version int bcd2 = 0; temporary = original; for (unsigned int i = 1000000000; i > 0; i /= 10) { bcd2 = (bcd2<<4)+temporary/i; temporary %= i; } std::cout.copyfmt(std::ios(NULL)); std::cout << "BCD 4bit int is " << original << "=" << std::hex << bcd2 << std::endl; return 0; }

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