GNU Smalltalk Library Reference: FileStream class-standard streams

stderr: Answer a FileStream that is attached the Smalltalk program’s standard error file handle, which can be used for error messages and diagnostics issued by the program.
stdin: Answer a FileStream that is attached the Smalltalk program’s standard input file handle, which is the normal source of input for the program.
stdout: Answer a FileStream that is attached the Smalltalk program’s standard output file handle; this is used for normal output from the program.