# User View

# System Programs

Provide a convenient environment for program development and execution.

• file management (i.e. rm, ls, ...)
• status information
• file modifications
• programming language support (i.e. java)
• etc.

# OS Interface for Users

# CLI

• text/keyboard based command entry

# GUI

• more user-friendly
• visual, using icons, buttons, etc.

# Operation

# User and Kernel Modes

Some instructions are 'privileged' which can only be ran in kernel mode (not the user mode). For the instruction to run, the mode has to be switched through the 'mode bit'. mode bit = 1 for user mode, mode bit = 0 for kernel mode.

# System Calls

Programming interface to the services provided by the OS.

• process calls (launch a program)
• file management
• device management
• information maintenance (i.e. syncing time)
• communications

These are typically written in a high(er)-level language like C or C++.