A deadlock in operating systems occurs when processes cannot proceed due to mutual waiting for held resources, forming a cycle. It requires four simultaneous conditions: mutual exclusion, hold and wait, no preemption, and circular wait. Deadlocks can be prevented, detected through algorithms, or resolved by terminating processes or reclaiming resources.

1. A deadlock in OS occurs when a set of processes is unable to proceed because each is waiting for a
resource held by another, forming a cycle of dependency. Deadlock arises when four conditions occur
simultaneously: mutual exclusion (resources can't be shared), hold and wait (processes hold
resources while waiting for others), no preemption (resources can't be forcibly taken), and circular
wait (a circular chain of processes exists). Deadlocks can be prevented by avoiding one of these
conditions, detected through algorithms, or resolved by terminating processes or reclaiming
resources.