To compile `metro_write.c` on MacOS 10.14 with XCode: $ clang metro_write.c -o metro Output: $ xxd metro_areas.bin 00000000: e207 0000 546f 6b79 6f00 0000 0000 0000 ....Tokyo....... 00000010: 0000 0000 0000 0000 4a50 01e7 1158 274c ........JP...X'L 00000020: df07 0000 5368 616e 6768 6169 0000 0000 ....Shanghai.... 00000030: 0100 0000 0e00 0000 434e 0000 f8a0 134c ........CN.....L 00000040: df07 0000 4a61 6b61 7274 6100 0000 0000 ....Jakarta..... 00000050: 0000 0000 0000 0000 4944 0000 bcc5 f14b ........ID.....K $ python3 metro_read.py 2018 Tokyo, JP 43,868,228 2015 Shanghai, CN 38,700,000 2015 Jakarta, ID 31,689,592