This means terse commands. UNIX is a time-slice operating system. Priorities of processes are dynamically adjusted to achieve fairness to all users. UNIX is not the optimal operating system for real-time control. UNIX commands and options are case sensitive .
Commands are lower case.
Options are either upper or lower case. Output will show-up on the terminal known as the console . The system does a series of power-up tests, including checking the filesystems and loading device drivers. The system switches into multi-user mode. Characters are not echoed to the screen during password entry.