gawk: uninit4.awk:4: warning: reference to uninitialized field `$0'

gawk: uninit4.awk:9: warning: reference to uninitialized field `$0'

gawk: uninit4.awk:10: warning: reference to uninitialized field `$0'

gawk: uninit4.awk:11: warning: reference to uninitialized field `$1'

gawk: uninit4.awk:12: warning: reference to uninitialized field `$2'