Here's a fancier, slightly less-magic, version. How to compile is left as an exercise for the reader (hint: Haswell or newer, requires BMI2 instruction set):

Here's a fancier, slightly less-magic, version. How to compile is left as an exercise for the reader (hint: Haswell or newer, requires BMI2 instruction set): void toBinary(uint8_t byte) { uint64_t zeroes = *(uint64_t *)"00000000"; uint64_t resultStr = zeroes | __builtin_bswap64(_pdep_u64(byte, 0x0101010101010101ULL)); printf("hello: %.*s\n", 8, (char *)&resultStr); }