A sequence of single character flags. When a character is present this indicates Vi-compatible behavior. This is used for things where not being Vi-compatible is mostly or sometimes preferred. 'cpoptions' stands for "compatible-options". Commas can be added for readability. To avoid problems with flags that are added in the future, use the "+=" and "-=" feature of ":set" |add-option-flags|. NOTE: This option is set to the Vi default value when 'compatible' is set and to the Vim default value when 'compatible' is reset. NOTE: This option is set to the POSIX default value at startup when the Vi default value would be used and the $VIM_POSIX environment variable exists |posix|. This means Vim tries to behave like the POSIX specification.