operating systems

Software layer managing hardware resources and providing an environment for programs to run. The bridge between silicon and algorithms.

core responsibilities

• process scheduling: allocating CPU time among competing tasks, context switching, priorities
• memory management: virtual memory, paging, allocation, protection between processes
• file systems: organizing persistent storage into hierarchical namespaces
• device drivers: abstracting hardware interfaces for uniform access
• security: user permissions, access control, isolation

types

• monolithic kernel: Linux, all services in kernel space
• microkernel: Minix, minimal kernel with services in user space
• exokernel: application-level resource management
• unikernel: single-application, library OS

key abstractions

The process, the file, and the socket. Everything in Unix is a file. Processes communicate through pipes, shared memory, and message passing. Sockets extend communication across networks.

relation to the stack

compilers produce binaries that the OS loads and schedules. databases rely on OS file systems and memory management. consensus algorithms run as distributed OS-level processes.