qmk_firmware/keyboards/c39/c39.h

#pragma once

#include "quantum.h"

#define ___ KC_NO

#define LAYOUT( \
    K00, K01, K02, K03, K04, K05, K06, K07, K08, K09, K0A, K0B, K0C, \
    K10, K11, K12, K13, K14, K15, K16, K17, K18, K19, K1A, K1B, K1C, \
    K20, K21, K22, K23, K24, K25, K26, K27, K28, K29, K2A, K2B, K2C  \
  ) { \
  { K00, K01, K02, K03, K04, K05, K06, K07, K08, K09, K0A, K0B, K0C }, \
  { K10, K11, K12, K13, K14, K15, K16, K17, K18, K19, K1A, K1B, K1C }, \
  { K20, K21, K22, K23, K24, K25, K26, K27, K28, K29, K2A, K2B, K2C }  \
}

#define LAYOUT_ortho_3x13 LAYOUT