I didn't know inttypes.h

gistfile1.c

#include <stdio.h>
#include <stdint.h>
#include <inttypes.h>

int main() {
  uint8_t u8 = UINT8_MAX;
  uint16_t u16 = UINT16_MAX;
  uint32_t u32 = UINT32_MAX;
  uint64_t u64 = UINT64_MAX;

  printf("%" PRIu8 "\n", u8);
  printf("%" PRIu16 "\n", u16);
  printf("%" PRIu32 "\n", u32);
  printf("%" PRIu64 "\n", u64);

  return 0;
}