Operating System

1. OPERATING SYSTEM GROUP ASSIGNMENT
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Submitted by AQSA FATIMA, REHA ANOUSH, RIMSHA AZMAT
GROUP MEMBERS: Reha, Rimsha, Aqsa Fatima
DEPARTMENT: C-I-S
ASSIGNMENT#: Group Assignment
SUBMITTED TO: MA’AM ANEELA USMAN

2. OPERATING SYSTEM GROUP ASSIGNMENT
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Submitted by AQSA FATIMA, REHA ANOUSH, RIMSHA AZMAT
QUESTION:
propose an idea and design a prototype for designing new
operating system. Define its goals/objectives, how it will manage
resources
ENOS
Definition:
ENOS “Emerging New Operating System” is a user friendly, Multiuser,
multitasking Operating system.
This overview is intended for new ENOS users who want a basic knowledge of
ENOS and for experienced users who want a list of commands and programming
tools. This overview is the ENOS manual you should read first. It introduces you
to the ENOS operating system and to the full set of ENOS manuals. After you
have read this manual, you should understand what an operating system is, be
familiar with basic ENOS concepts and terminology, have an overall view of
what is included in the system, and understand what information is presented in
each manual in the set of ENOS manuals.
Management of Processes:
Processes are programs being executed. Each time a program is executed, a
process begins. It is unique and is identified by a number called a PID (process
ID). Like directories, processes are organized into hierarchies. The first process
(PID 1) begins when the system administrator starts the system, and all processes
descend from process 1 in parent-child relationships. For example, when process
1 starts process 2, process 1 is the parent and process 2 is the child.
A process begins as a result of an exec system call or a fork system call. An exec
replaces another process and takes its PID. It is used when one process is finished
and will not be needed again. A fork starts a child process and continues to let the
parent process run. The child process inherits all of the open files of the parent
but is separate from the parent and has its own PID. The parent process either
waits until the child process ends, or the parent continues to run while the child
is running
Features:
The features of ENOS include:

3. OPERATING SYSTEM GROUP ASSIGNMENT
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Submitted by AQSA FATIMA, REHA ANOUSH, RIMSHA AZMAT
• Multiuser
• Multitasking
• AT&T ENOS base
• Supporting libraries,
• text editor
• semaphores
• file locking.
New Features:
The new features we would like to introduce in ENOS operating system are as
follow:
Firewalls
The first key idea I wish to discuss is ``firewalls''. The familiar expression “good
fences make good neighbors” applies to programs as well as to people.Firewalls
are defined in this new Updated version of Operating system.
Firewalls are barriers that prevent one section of an application from affecting
other sections except through well defined interfaces. The most common kind of
firewall is the kind provided by OS between jobs or by VM between virtual
machines. Gnosis provides this kind of protection between parts of an application
as well as between applications. Gnosis does this by allowing a program to be
broken up into many pieces which we call ``domains''. Each domain has its own
address space, registers, PSW, and authority. The authority of a domain is
represented by tokens called ``capabilities''. These capabilities are kept in operating
system space and manipulated by system calls.

4. OPERATING SYSTEM GROUP ASSIGNMENT
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Submitted by AQSA FATIMA, REHA ANOUSH, RIMSHA AZMAT
Capabilities represent such diverse authority as the authority to expend resources,
the authority to access a particular piece of data, and the authority to call a
particular program. Domains communicate with each other by invoking their
capabilities with system calls.
Hiding Things
The second important idea in ENOS that I want to talk about is ``hiding things.''
In ENOS it is possible to hide the details of the implementation of certain functions
from the programs that use those functions.
Hiding things allows us to reduce the conceptual complexity of certain functions.
In our example the complexity of the database can be hidden behind an interface
that just provides for retrieval, update, insertion, and deletion of reservations. This
allows the programmer who is manipulating the data to ignore all the many facets
of the database, for example performance options, that are not relevant to his
current problem.

5. OPERATING SYSTEM GROUP ASSIGNMENT
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Submitted by AQSA FATIMA, REHA ANOUSH, RIMSHA AZMAT
User Replaceable Units
The last key idea I with to discuss today is ``user replaceable units.'' This idea leads
directly to the end of monolithic operating systems.
Operating systems have had the problem of trying to control size and complexity.
MVS, for example, has divided the privileged code into seven protection keys as
an attempt to isolate parts of the operating system from each other. VM has divided
its operating system function into the protected security kernel which is called CP,
and the unprotected function, which includes directories and virtual storage
management, which is called CMS.
Memory:
The first port of ENOS 8086 was to Altos. Altos had several machines which
implemented this hardware configuration. There were a couple of compatible
versions called, I think, 8600 and 586. this had an 8086 CPU connected to a
Memory Management Unit (MMU) which allowed a level of demand paging. it
didn't support page faults or any such niceties, but it did allow a reasonable level
of swapping. Real mode 8086 doesn't support any of this. I don't think it had a

6. OPERATING SYSTEM GROUP ASSIGNMENT
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Submitted by AQSA FATIMA, REHA ANOUSH, RIMSHA AZMAT
general bus but it did support an 8087 and extra memory. The port was done in
late 1980 and early 1981 by Gordon Letwin and the first version shipped in the
Autumn of 1981. The second port was also done by Gordon in late 1981 for Intel.
The first prototype we got from Intel had a square front about a foot on a side and
was about 20 inches deep. I can't remember what it was called, but it had an 8-
inch floppy drive oriented vertically, in addition to the internal hard disk. it was
built around a Multibus backplane. by early '82 it had been replaced by a similar
box using 5" floppies and I think a 20MB hard disk in the same cubic format, and
a couple of years later a flatter white box more typical of the desktop
configurations of the era.
The first SCO real mode port of ENOS didn't come along until 1983--two years
after Gordon's original--and it didn't work well for more than a year after (or ever,
really--it's unmapped 8086...). By this point the 286 was available, which had a
real memory map on the chip, so there was little point in continuing with 8088 or
8086 real mode. (a memory map helps several things: it allows more physical
memory to be available than the address space of the machine (1MB in the case
of the 8086, and only 640K on the PC).
Pros/crons:
There are no advantages or disadvantages to ENOS, since it has no practical
application for use in today's world. Like CP/M or System 1 on the Macintosh,
ENOS cannot even be compared properly to modern systems.
Improvements:
Trusted ENOS was a variant initially developed by IBM, under the name Secure
ENOS; later versions, under the Trusted ENOS name, were developed by Trusted
Information Systems. It incorporated the Bell-LaPadula model of multilevel
security, and had a multilevel secure interface for the STU-III secure
communications device (that is, an STU-III connection would be made available
only to those applications running at the same privilege level as the key loaded in
the STU-III). It was evaluated by formal methods and achieved a B2 security
rating under the DoD's Trusted Computer System Evaluation Criteria—the
second highest rating ever achieved by an evaluated operating system. Version
2.0 was released in January 1991, version 3.0 in April 1992, and version 4.0 in
September 1993. It was still in use as late as 1995.