The document outlines the requirements for operating system (OS) process management, emphasizing the need for interleaved execution of processes to enhance CPU utilization and response time. It details process attributes, such as unique identifiers, states, priorities, and resource management, alongside the role of the OS in controlling process interactions and resource allocation. Additionally, the document touches on process states and the distinctions between user mode and kernel mode in Unix SVR4 process management.

1. PROCESS DESCRIPTION AND
CONTROL

2. Processes requirements

3.  The OS must interleave the execution of
multiple processes, to maximize processor
utilization while providing reasonable
response time.
 The OS must allocate resources to
processes in conformance with a specific
policy (e.g., certain functions or
applications are of higher priority) while at
the same time avoiding deadlock.
 The OS may be required to support
interprocess communication and user
creation of processes, both of which may
aid in the structuring of applications

4. WHAT IS A PROCESS?

5.  A program in execution
 An instance of a program running on a
computer
 The entity that can be assigned to and
executed on a processor
 A unit of activity characterized by the
execution of a sequence of instructions, a
current state, and an associated set of
system resources

6. Process Control

7. Process Control Block (PCB)
 Identifier: A unique identifier associated with this process, to
distinguish it from all other processes.
 State: If the process is currently executing, it is in the running state.
 Priority: Priority level relative to other processes.
 Program counter: The address of the next instruction in the
program to be executed.
 Memory pointers: Includes pointers to the program code and
data associated with this process, plus any memory blocks shared
with other processes.
 Context data: These are data that are present in registers in
the processor while the process is executing.
 I/O status information: Includes outstanding I/O requests, I/O
devices (e.g., tape drives) assigned to this process, a list of files in
use by the process, and so on.
 Accounting information: May include the amount of processor
time and clock time used, time limits, account numbers, and so
on.

9. PROCESS STATES
 A very simple
example. A small
dispatcher program
that switches the
processor from one
process to another.
A process to
continue execution
for a maximum of
six instruction
cycles

10. A Two-State Process Model

12. Reason for proses creation

15. A Five-State Model

17. Description

18. PROCESS DESCRIPTION

19.  The OS controls events within the computer system. It
schedules and dispatches processes for execution by the
processor, allocates resources to processes, and responds to
requests by user processes for basic services. Fundamentally,
we can think of the OS as that entity that manages the use of
system resources by processes.

21. PROCESS CONTROL

22. UNIX SVR4 PROCESS MANAGEMENT
 Process States
• UNIX employs two Running states to indicate whether the
process is executing in user mode or kernel mode.
• A distinction is made between the two states: (Ready to
Run, in Memory) and(Preempted).These are essentially the
same state, as indicated by the dotted line joining
them.The distinction is made to emphasize the way in
which the preempted state is entered.When a process is
running in kernel mode (as a result of a supervisor call,
clock interrupt,or I/O interrupt), there will come a time
when the kernel