Process Management

Question 1

What is process creation ?

Answer 1

Processes can be created by another program or process.
The act of creation is called spawning.
Each processes is represented by a Process Control Block (PCB).

Question 2

Give an example of process creation in a UNIX command line

Answer 2

startup = sched
ancestor = init
fork() = duplicate process
exec() = replace child with new program

Question 3

What is process scheduling ?

Answer 3

Only one process runs at a time.
Others wait in memory / disk.
Context switching (from one process to another) is time consuming.

Question 4

What are the process scheduling levels ?

Answer 4

High Level (HLS): Admit or reject new processes
Medium level (MLS): Suspend or resume processes
Low-Level (LLS): Pick the next process for the CPU

Question 5

What is the the three state model ?

Answer 5

READY - waiting for CPU
RUNNING - executing
BLOCKED - waiting for I/O

Question 6

What transitions are involved in the three / five state model ?

Answer 6

dispatch, timeout, I/O wait, I/O Completion, termination.

Question 7

What is the five state model ?

Answer 7

Adds READY SUSPENDED, and BLOCKED SUSPENDED

Question 8

What is the process life cycle ?

Answer 8

READY –> RUNNING,
RUNNING –> BLOCKED (after I/O request),
BLOCKED –> READY (once I/O completes),
READY –> RUNNING (when CPU is available)