Operating systems and utility software

The software that runs everything

• On its own, hardware only fetches and runs instructions — it knows nothing of files, programs or users.
• The operating system is the software layer that manages it all.
• It also bundles utility programs to keep the system healthy.

What an operating system does

• Manages the hardware (processor, memory, I/O, storage) for the running programs.
• Provides services (file system, network, accounts) through a clear interface, so programs don't talk to hardware directly.
• Provides a user interface (command line, GUI, touch).
• Lets several programs share the hardware safely — each gets fair CPU time and is kept out of the others' memory.

Key management tasks

• Process management — load programs, schedule them on the CPU, switch between them. (A running program is a process.)
• Memory management — give memory to processes, keep them apart, and use virtual memory / paging so the working set can exceed physical RAM.
• File management — organise files/folders on storage, control permissions.
• Device management — handle I/O via device drivers, buffer data, manage interrupts.
• Plus security (accounts, permissions, firewall) and networking.

Utility software

• Disk defragmenter — gathers the pieces of fragmented files together on a hard disk to cut seek time (not useful on SSDs).
• Backup — copies data elsewhere for recovery.
• Antivirus — scans for malware and quarantines threats; firewall — filters network traffic.
• Compression, system monitors and updates round it out.

You've got it