Editing SAIL (programming language) (section)

===Input/Output===
SAIL's [[input/output]] system was based on the idea of numbered "channels" in a fashion somewhat similar to the scanner entries. To open a file, one first called {{code|GETCHAN}} to return a value of a free channel, and then {{code|OPEN}}ed it with various parameters to describe the file and modes of operation. {{code|RELEASE}} was equivalent to close. Once opened, the file could be read, subject to the scanning rules noted above, by calling {{code|INPUT}} and looking for the end-of-file. Files did not have names as part of the OPEN, instead, {{code|LOOKUP}} could be used to point a channel at a given file, {{code|ENTER}} made a new file associated with a channel, and {{code|RENAME}} allowed an existing file name to be changed.{{sfn|Smith|1976|p=32}} One can open an existing file for writing using {{code|GETCHAN... OPEN... LOOKUP... ENTER}}.{{sfn|Smith|1976|p=33}}

There were numerous special handlers and variables that were used during I/O. For instance, the {{code|INCHWL}} function was an INPUT hard-wired to the user terminal and always open, and it returns its break character in the system variable {{code|!SKIP!}}.{{sfn|Smith|1976|p=30}} The {{code|PRINT}} function normally output to the same terminal channel, but could also be directed at any other opened channel.{{sfn|Smith|1976|pp=2, 38}}