running and when reset to 1, the process is allowed to run],

[| Signals (messages) dispatch table [process [PC functions].

ட OS allocated resources‘descriptors (for example, file descriptors for open files, device
descriptors for open (accessible) devices, device-buffer addresses and status, socket

descriptor for open socket),and

[| Security restrictions and permissions.

Context
— Conlexl Joads into the CPU registers from memory when process starts running, and the

registers save at the addresses of register-save area on the context switch to another process

[1 The present CPU registers, which include program counter and stack pointer

context
[| When context saves on the PCB pointed process_gtack and register-s ave area addresses,

then the running process stops.

[1 Other process context now loads and that process runs- This means that the context has

switched.
are called

Threads and Tasks Thread

Concepts
[1 A thread consists of executable program (codes). sate of which is controlled by OS, -

‘| The state information sp -ead-status (running, blocked, or finished), thread structure—

its data, objects and a subset of the process resources, and thread-stack. Considered a
lightweight process and a process level controlled entity.[Light weight means its running

does not depend on system resources] .