バージョン：25.2
- open file filename [for purpose]
- purpose may be one of: reading, writing, readWrite, appending, updating
- for reading -- file must exist, only reading of the file will be allowed
- for writing -- if file doesn't exist, it will be created. If it does exist, it will be overwritten.
- for readwrite -- if file doesn't exist, it will be created, both reading and writing allowed
- for appending -- same as for writing, but seeks to end of file when first opened
- for updating -- file must exist, both reading and writing are allowed
- Related: close file, read, write