An operating system acts as an interface between a computer's user and its hardware, providing convenience, efficiency, and the ability to evolve over time. Operating systems have evolved from simple batch systems to today's multi-tasking, distributed, and real-time systems that allow many users and programs to run simultaneously on networked computers.

1. An operating system is a program
that acts as an interface or
intermediary between the user of a
computer and the computer
hardware.

2. OBJECTIVES AND FUNCTIONS
• Convenience
• Efficiency
• Ability to Evolve

3. Evolution of Operating Systems
• Simple batch systems
• Multi programmed systems
• Time Shared Systems
• Parallel systems
• Distributed Systems
• Real time systems