User Interfaces -Means by which users can issue commands to system a command -line interface(e.g sh, csh, ksh, tosh, etc. ) a gui interface(e.g. Windows, X-Windows, KDE, Gnome, etc. or a batch command systems. The latter are generally older systems using punch cards of job-control language, JCL, but may still be used today for specialty systems designed for a single purpose• User Interfaces - Means by which users can issue commands to the system. • a command-line interface ( e.g. sh, csh, ksh, tcsh, etc. ), • a GUI interface ( e.g. Windows, X-Windows, KDE, Gnome, etc. ) • or a batch command systems. The latter are generally older systems using punch cards of job-control language, JCL, but may still be used today for specialty systems designed for a single purpose