Operating System (OS)
Assembler language

requires fixed-format commands
None of these
is a mnemonic form of machine language
is quite different from the SCL interpreter
is usually the primary user interface

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Operating System (OS)
The advantage of a command processor running only built-in commands is:

the processing is much faster than would other-wise be the case when user defined commands are used
users can create system programs and run them as commands
the command set being common across different hardware configurations
None of these
flexibility to the users in running lists of commands by simply collecting them in named batch command files

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