IBM OS/2 Analysis

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An Analysis on the
International Business Machines Operating System 2
(IBM OS/2)
Submitted by:
BETCpET – 2A/B – Non-STEM
Evangelista, Luigi Miguel M.
Insigne, Janssen Harvey P.
Magat, Ralph Gerard B.
Medina, Jorge Ivan P.
Rosales, Jhon Lelan C.
JULY 2020

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TABLE OF CONTENTS
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I. History of the Operating System. . . . . . . .3
A. Background and Developer. . . . . . . .3
II. Analysis of the Operating System. . . . . . . .6
A. Versions. . . . . . . . . . .6
B. Development. . . . . . . . . .13
C. Hardware Ran. . . . . . . . . .14
D. CPU Allocation Scheme. . . . . . . .14
E. Memory management. . . . . . . . .15
F. Virtual Memory. . . . . . . . . .18
G. Secondary Storage Management. . . . . . .19
H. Networking and Cloud Capabilities. . . . . . .21
III. Conclusion. . . . . . . . . . .23
IV. References. . . . . . . . . . .24
V. Appendix. . . . . . . . . . .25
A. Work Participation of the Members. . . . . . .25

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I. HISTORY OF THE OPERATING SYSTEM
A. BACKGROUND AND DEVELOPER
IBM is, perhaps, the best-known computer company in the world. It began as the
Computing, Tabulating & Recording Company (C-T-R) founded by Herman Hollerith in
the late 1800s. Their first large contract was to provide tabulating equipment for the
tabulation and analysis of the 1890 US census.
The company grew quickly and, in the early 1920s the name was changed to IBM.
IBM was the world leader in providing computer systems for both business and scientific
applications.
When, in 1964, they revolutionized the industry by bringing out the first
comprehensive family of computers (the System/360) it caused many of their competitors
to either merge or go bankrupt, leaving IBM in an even more dominant position.
The advent of smaller computers, and IBM’s failure to compete effectively in this
field initially, caused some financial problems but IBM remains a major force in the
industry.
IBM developed Sequek in 1974 and got renamed 2 years later to SQL (Structured
Query Language), the publications about the Relation model of E. F. Codds was the basis
for this development. The cost for the development of the operating system OS/360 was
50 million dollars and it has more than 220,000 lines of code. The operating system
OS/400 were renamed since release V5R3 to i5/OS. E.g. This OS is used for example on
the eServer i5 with PowerPC processors. The new IBM System /360 is a more efficient
computer system as previous IBM computers which is different built up. The hardware
components (like the card reader) were interchangeable and the software can operate on
all models of the product family. The development of System 360 cost 5 billion dollars
and employed in record times over 50,000 employees. This computer was manufactured
for the first time with an assembly line.
IBM OS/2, in full International Business Machines Operating System/2, an
operating system introduced in 1987 by IBM and the Microsoft Corporation to operate the
second-generation line of IBM personal computers, the PS/2 (Personal System/2). It was
intended to replace the older disk operating system (DOS), which, with the development

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of the Intel Corporation 80286 microchips in the mid-1980s, was growing increasingly
obsolete. OS/2 combined a new graphical user interface (GUI) with features previously
available only on mainframe computers. It shared similarities with other personal
computer (PC) operating systems, including Microsoft Windows, UNIX, and Xenix.
Simultaneously, Microsoft continued development of its Windows operating
system, who’s popular third iteration (Windows 3.0) contained some of the GUI elements
developed for OS/2. Despite later basing some Windows NT and Windows 95
developments on code written for IBM and OS/2, Microsoft soon discontinued
development of further interface features for OS/2.
With Microsoft focusing its efforts on Windows, IBM turned to Commodore
Business Machines for interface development and borrowed GUI design ideas from the
Commodore AmigaOS. With OS/2.20 the WorkPlace Shell was created and became a
GUI standard, and future OS/2 iterations ran Windows with a reliability that led IBM to
label the system “crash proof.”
In 1994 IBM introduced a new version, OS/2 Warp, which included many new
features. OS/2, however, failed to acquire a share of the mass market. It survived in IBM-
dominated niche markets such as automated teller machines (ATMs), but the company
halted production in 2005 and support in 2006. Users and developers still loyal to OS/2
support releasing the software as open source, but Microsoft retains rights to some of the
code, and the security of ATMs could be compromised.
In the early and mid-1980s DOS was the king of operating systems for personal
computers. With the coming of newer, faster machines such as Intel's 80386 a new
operating system was needed that could use the more powerful and faster hardware;
OS/2 was IBM’s answer. OS/2 was a joint venture between IBM and Microsoft, where
IBM was in charge of development of the core operating system and Microsoft was to
handle the design and implementation of the graphical interface; "The lead architects of
OS/2 on the Microsoft side was Gordon Letwin and on the IBM side it was Ed Iacobucci
(later co-founder and CEO of Citrix)" (Necasek, 1998).
In 1987 OS/2 version 1.0 came out, some features included preemptive
multitasking, inter process communication, virtual memory support and multithreading.
OS/2 version 1.1 came out a year later and was basically the same system but included

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an easier to use graphical user interface. However, Windows version 1.0 came out a
couple of years prior to OS/2 and despite not being as reliable an operating system, was
generally accepted by the general public because it was easier to use. OS/2 did not
generate revenue as IBM hoped, as many users decided not to switch from Windows to
OS/2.
In late 1989, OS/2 version 1.2 hit the marketplace- its most improved feature was
its use of the High-Performance File System, which was faster than FAT. In 1990,
Windows 3.0 was released and again Windows outsold OS/2. Again, it seemed that most
of the buying public preferred to stay with the familiar but unreliable Windows as opposed
to experimenting with the “new” product OS/2. For whatever reason this would remain the
fate of OS/2 in the marketplace. Some blame it on poor marketing and planning by IBM,
while others blame the lack of success on Windows being an easier system to use.
Regardless of the reason, OS/2 never became a dominant operating system for personal
computers. (Both, 2000)
When OS/2 version 1.2 was released, Microsoft broke off its partnership with IBM
and focused its efforts on their Window’s system. OS/2 v.1.3 came out a year later and
was developed solely by IBM, which resulted in a smaller, more compact operating
system. OS/2 version 2.0 came out in 1993 and was a 32-bit OS. Many other versions
of OS/2 where undertaken by IBM and almost all of them were failures when it came to
sales. The OS/2 for PowerPC was the most embarrassing failure for IBM where billions
were put into a product that never fully made it to the shelves. (Both, 2000)
The most important and impressive version of OS/2 was OS/2 Warp that came out
in 1994 and thoroughly out-performed Windows. Warp was not founded on the unreliable
DOS like Windows 3.1 and 95. It was easier to use than previous OS/2 systems and it
supported the Internet, albeit crudely, long before Microsoft had incorporated it into their
systems. Although it was a better overall system then Windows, Windows 95’s upcoming
release again hurt IBM and again sales for the OS/2 warp were disappointing. OS/2 warp
had a few versions and improvements, but IBM had all but given up its resources toward
the production of more OS/2 products and very few if any still run OS/2 for practical
reasons (Nacask, 1998)

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II. ANALYSIS OF THE OPERATING SYSTEM
A. VERSIONS
IBM OS/2 Warp
Main characteristics of OS/2 (Operating System 2) are primarily the simple and
powerful user interface WPS (Workplace Shell), stability and technology lead in the earlier
years of OS/2. The user interface is built up completely object-oriented. OS/2 of IBM does
not have to be compared with DOS or Windows extensions any more since the version
2.0. This new version corresponded to a new operating system generation, which has the
potential to use the full performance of a 32-bit CPU, developed only by IBM. Up to
version 1.3 IBM had cooperated in development with Microsoft. The beta version was
tested by 30,000 voluntaries. It was made under the slogan to create a "Better DOS than
DOS" with success. Much programs for DOS and Windows (3.x, Win32s) are executed
faster under OS/2 than in the original operating environment. The project Odin has the
destination to execute Win32 programs (Windows 9.x and Windows NT) in OS/2 Warp
natively. This happens by conversion of the .EXE and .DLL files into the OS/2 format or
about adjustment of the program code copy in the memory as in the case of OS/2
programs. Said more exactly, the PE (Portable Executable) Win32 binary format get
converted into the OS/2 LX binarily (linear eXecutable) format.
IBM OS/2 Warp 4 and 4.5
OS/2 Warp 4 was released by IBM in 1996. Because of the long-lasting support by
IBM this operating system is holed up to date through service releases and newer
hardware drivers to use OS/2 on current computer systems. Until May 2001 the service
release 15 and the Device Driver Pack 2 are free of charge. With this update the system
version 4.0 (rev. 9.023) was upgraded to version 4.5 (rev. 14.096 c_W4). After this release
IBM grants newer updates only in context of the software subscription with costs.
Furthermore, free of charge are additions and driver software to support new fixed disk
controllers as well as ATAPI devices. Indispensable are the driver software of Daniela
Engert which completely replace the IBM standard driver software. With these new
drivers large FAT 32 partitions are accessible without problems and the drives operates
now in the DMA mode instead of the much slower PIO mode.

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OTHER VERSIONS AND ITS FEATURES
OS/2 1.0—December 1987—Originally CP/DOS
• Joint IBM-Microsoft development
• 16-bit protected-mode, multi-threaded, multi-tasking OS
• Segmented virtual memory
• 286 CPU and about 1.5 MB RAM required
• Maximum 32MB partition size
• FAT filesystem only
• Text mode, DOS-like interface
• Single DOS box support
OS/2 1.1—November 1988—Codename Trimaran
• Presentation Manager graphical user interface (codename Winthorn)
• Support for larger than 32MB partitions
• 3-4 MB RAM minimum

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OS/2 1.2—October 1989—Codename Sloop
• Installable Filesystem (IFS) support
• HPFS filesystem included
• Improved Presentation Manager
• Dual Boot capability
• REXX and IPF support
OS/2 1.3—December 1990—Codename Cutter
• Lowered resource requirements (2 MB RAM)
• ATM font support
• Developed primarily by IBM
OS/2 2.0 LA—December 1991—Limited Availability
• Internal revision 6.177 (91/12/11)
• Pre-release version of OS/2 2.0
• Only for selected IBM customers, officially supported
OS/2 2.0—April 1992—Codename Cruiser
• Internal revision 6.307 (92/03/01), XR02000
• 32-bit protected-mode, multi-threaded, multi-tasking OS
• Paged virtual memory
• 386 CPU and 4 MB RAM required
• Multiple DOS boxes
• Win-OS/2 support (based on Windows 3.0)
• System Object Model (SOM) support
• Workplace Shell (WPS) graphical interface
• Boot Manager included
• Limited hardware support
OS/2 2.00.1—October 1992—Codename Riker
• Only preloaded on IBM hardware
• 32-bit Graphics Engine (GRE)
• XGA-2 support

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• Similar to Service Pak XR06055
OS/2 2.1—May 1993—Codename Borg (previously Yawl)
• Improved non-IBM hardware support
• APM and PCMCIA support
• MMPM/2 included
• Win-OS/2 based on Windows 3.1
OS/2 for Windows—November 1993—Codename Ferengi
• Used pre-existing Windows 3.x instead of Win-OS/2
• New drivers for S3 based cards
• Largely unchanged from original 2.1 release
OS/2 2.11—February 1994
• Also available as Service Pak XR06200 for OS/2 2.1
• Bugfix release
OS/2 2.11 SMP—July 1994
• Internal revision S.624 (94/06/09), XR02014
• Symmetric Multiprocessing (SMP) support
• Up to 16 CPUs supported
• Only sold with SMP hardware
OS/2 Warp—October 1994—Codename Warp
• Performance tuned, lower resource requirements
• Compatible with Windows 3.11
• BonusPak (with Internet Access Kit) included
• Improved hardware support
• Updated WPS
OS/2 Warp with Win-OS/2—February 1995

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• Same as above but with Windows 3.1 included
OS/2 Warp Connect with Win-OS/2—May 1995
• Networking support included (MPTS, TCP/IP, LAN Requester)
• Peer-to-peer networking
OS/2 Warp Connect—July 1995
• Same as above but without Windows 3.1
OS/2 Warp, PowerPC Edition—December 1995
• IBM Power Series hardware support
• Based on MACH microkernel
OS/2 Warp Server 4—February 1996
• Internal revision 8.234, XR03005
• Combined OS/2 Warp and LAN Server
• Entry and Advanced editions (the latter with HPFS386)
OS/2 Warp 4—September 1996—Codename Merlin
• Updated WPS, new look and feel
• Java 1.0.1 and JDK included
• VoiceType included
• OpenGL (software renderer only) support
• OpenDoc included
OS/2 Warp Server Advanced SMP—September 1996
• Warp Server 4 Advanced with SMP support
• Free upgrade for Warp Server Advanced licensees
WorkSpace On-Demand 1.0—November 1997—Codename BlueBird
• Based on OS/2 Warp 4
• Required OS/2 Warp Server
• RIPL remote boot

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• Centralized client deployment and management
WorkSpace On-Demand 2.0—October 1998
• Added fully diskless PXE client boot support
• Improved client manageability
• Easier management through the LAN Server GUI
OS/2 Warp Server for e-Business—April 1999—Codename Aurora
• Internal revision 14.039F, XR04500
• SMP support
• JFS filesystem support
• Limited 32-bit device driver support
• High memory support (more than 512 MB per process)
• Improved internationalization
• NetFinity 5.2 included
• Lotus Domino Go Webserver 4.6 included
• WebSphere Application Server 1.1 included
• Version 4.50
OS/2 Convenience Pack 1—November 2000—Known as MCP/ACP
• Based on WSeB kernel
• Java 1.1.8 included
• Programmer’s Toolkit included
• Version 4.51
OS/2 Convenience Pack 2—November 2001—Known as MCP2/ACP2
• IBM Web Browser included
• Java 1.3 included
• Innotek Flash included
• Version 4.52
OS/2 Convenience Pack 2 Refresh—April 2002

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• Last OS/2 release
B. DEVELOPMENT
The development of OS/2 began when IBM and Microsoft signed the "Joint
Development Agreement" in August 1985. It was code-named "CP/DOS" and it took two
years for the first product to be delivered. OS/2 1.0 was announced in April 1987 and
released in December. The original release is textmode-only, and a GUI was introduced
with OS/2 1.1 about a year later. OS/2 features an API for controlling the video display
(VIO) and handling keyboard and mouse events so that programmers writing for protected
mode need not call the BIOS or access hardware directly. Other development tools
included a subset of the video and keyboard APIs as linkable libraries so that family mode
programs are able to run under MS-DOS and, in the OS/2 Extended Edition v1.0, a
database engine called Database Manager or DBM (this was related to DB2, and should
not be confused with the DBM family of database engines for Unix and Unix-like operating
systems). A task-switcher named Program Selector was available through the Ctrl-Esc
hotkey combination, allowing the user to select among multitasked text-mode sessions
(or screen groups; each can run multiple programs). Communications and database-
oriented extensions were delivered in 1988, as part of OS/2 1.0 Extended Edition: SNA,
X.25/APPC/LU 6.2, LAN Manager, Query Manager, SQL.
The promised user interface, Presentation Manager, was introduced with OS/2 1.1
in October 1988. It had a similar user interface to Windows 2.1, which was released in
May of that year. (The interface was replaced in versions 1.2 and 1.3 by a look closer in
appearance to Windows 3.1).
The Extended Edition of 1.1, sold only through IBM sales channels, introduced
distributed database support to IBM database systems and SNA communications support
to IBM mainframe networks.
In 1989, Version 1.2 introduced Installable Filesystems and, notably, the HPFS
filesystem. HPFS provided several improvements over the older FAT file system,
including long filenames and a form of alternate data streams called Extended Attributes.
In addition, extended attributes were also added to the FAT file system. OS/2- and

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Windows-related books of the late 1980s acknowledged the existence of both systems
and promoted OS/2 as the system of the future.
C. HARDWARE RAN
IBM designed the original version of OS/2 to make use of the improved abilities
and performance on the new group of personal computers such as Intel’s 80286 and the
80386. “These processors allow for a much greater amount of physical memory, will run
much faster, allow for the running of multiple tasks, and also allow for running applications
in both the real mode and the protected mode” (Campbell, p.9). OS/2 additionally could
support most of the common printers, hard drive, disk drives, monitors of the day. IBM
designed OS/2 to be able to run on their PC’s and Intel’s but did not allow OS/2 to be run
Apple’s Mac computer for obvious competitive reasons. The later versions of OS/2,
including the newest incarnation OS/2 Warp, generally kept pace with new PCs being
released at breakneck speeds. As the newer versions were released IBM also expanded
OS/2’s hardware compatibility so that the operating system could be run on various
competitors’ machines (i.e. the various models of Dell, Compaq, Gateway, etc.).
Additionally, OS/2 provided networking capabilities and therefore supported
communication devices such as modems and Ethernet cards.
D. C.P.U. ALLOCATION SCHEME
OS/2 also has certain microprocessor requirements. As mentioned before, it runs
on the Intel 80286 microprocessor or higher. Any Intel microprocessors before this do
not contain the necessary functions for the operating system, such as the ability to use
pages. Other microprocessors may be used if they have the ability to use pages for
memory. OS/2 also requires at least 2 MB of RAM to run both the OS/2 and DOS
execution environments.
OS/2 provides a utility called dynamic link call/return API. This utility allows
cooperative processing as a modular base for applications to extend. The base provides
real-time interrupt driven hardware and multitasking.

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E. MEMORY MANAGEMENT
The great advantage of OS/2 over its predecessor, the Microsoft DOS operating
system, in that it can address memory segments of up to 16 Megabytes. As well the OS/2
manages memory in a protected mode. This means that when a program attempts to
access an illegal memory address the operating system will be able to catch this illegal
access and deal with which will not end up crashing the system. The OS/2 also supports
the use of virtual memory. Virtual memory is where the operating system makes use of
the extra hard disk space when a program requests more memory than which is currently
available. OS/2 is also capable of sharing memory with applications.
Using DOS calls to Allocate Memory:
The OS/2 can allocate blocks of memory up to 64KB by calling the DosAllocSeg
function. In the ‘C’ programming language the call would take the form of DosAllocSeg
(Size, &Selector, Flags). Whenever a program requests memory in OS/2, this is what it is
called. The ‘Size’ parameter, which is used to select how big the memory segment should
be, can be in a range from 1 to 65,536 bytes. If a program needs to have the maximum
size allotted, then you would set the size to zero. The DosAllocSeg will return an error
code if memory allocation fails, or it will return a zero if it succeeds.

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Next, the DosAllocSeg call stores the selector variable, which can also be thought
of as the segment address into a descriptor table. This descriptor table holds the actual
physical addresses and the length of the memory segments. These descriptor tables are
not accessible by the application programs (Microsoft Systems Journal, 1987). We must
note here that the selector variable is not actually the physical address of the memory.
The selector is then converted into a pointer variable which includes a segment and an
offset. The selector, which is returned from the DosAllocSeg is the upper 16 bits of the
pointer. The last step in the DosAllocSeg call is to push the parameters onto the stack
beginning with the size parameter and then the address where the operating system will
store the selector. The DosAllocSeg offers the option to completely discard the memory
segment. This is what the third flag does in the call.
When the operating system needs more memory then it has available for main
memory it will save a memory segment to the hard disk to free up space. It uses the LRU
algorithm, or the least recently used algorithm to do this. When the segment is requested
again, the operating system must reload it back into main memory. This is the normal
operating instruction for the OS/2 when there is a program that requires more memory
than is available at the time. However, setting the flags in the DosAllocSeg call will tell the
operating system to completely throw out the memory segment if space is needed,
without saving the memory segment to disk first.
In addition to calling the normal method to allocate memory to programs, there are
also functions that will allow the operating system to change the size of a particularly
allocated piece of memory to allow more efficient use of it. To change the size of a
memory, block a typical call in the OS/2 operating system would use the DosReAllocSeg
(NewSize, Selector) call. A program is as well able to free up a block of memory in which
it no longer needs by calling the DOS call DosFreeSeg(). The OS/2 does automatic
memory allocation in that it will free up any memory when the application using that
memory terminates.
Shared Memory and Dynamic Linking
The OS/2 operating system was also used widely as a network operating system,
meaning that multiple users could have access to the same files/ programs at one time.
In order to allow for this the operating system must be able to allow for shared memory

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segments. A parent process is currently in execution and then another user logs onto the
system and requests the same program through a child process. This new process does
not necessarily have to create a whole new memory block for that user to be able to run
the program, but it can harness that memory space that the parent process is using.
Obviously, this entails sharing of just the program source code and separate areas of
memory will need to be created for users who wish to write to a file. Sharing memory
segments is done in the OS/2 using the DosGiveSeg command. It takes the parameters,
Selector, ProcessID, and &NewSelector. The ProcessID refers to the new program that
will receive the memory. Programs may also use the DosGetSeg command to gain
access to a block of memory allocated by another program. Next, we can use the
DosAllocShrSeg command to give a memory block a name when it is allocated. The name
will look almost exactly like a file except that it will start with an extension of SHARMEM
(therefore an example of a segment name would be SHAREMEM appname). One caveat
to this scheme is that only one named memory block with that unique name can be
running at a time. But as we have seen with the functionality of the DosGetSeg command,
we can see that by using the DosGetShrSeg command another process can have access
to the shared memory block (Petzold, 1988).
Along the topic of memory-sharing, something can be said about the way in which
memory is shared can be said about the MS-DOS operating system alongside the OS/2.
With the MS-DOS operating system linked libraries for programs were hard coded into
the programs themselves. With the OS/2, however, the .exe header file of programs
allows run time binding of the libraries. Thus, the overall effect of this type of sharing
allows library routines to be shared between multiple processes and saves memory space
as well (Microsoft Systems Journal, 1987).
Memory Protection
It is important to be able to protect memory segments because we do not want
programs accessing illegal segments which could cause the operating system to crash.
OS/2 provides some memory protection via the memory segment attributes. Each
memory segment holds attributes as to how it can be accessed i.e.: “ex” for executable,
“ro” for read-only and “rw” for read-write access. Each process local descriptor table
enforces memory protection between programs. If a program attempts to load a segment

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register with a selector, which is not valid for its own descriptor table, then the operating
system will generate a hardware interrupt. The OS will take control to remedy the situation
(Microsoft Systems Journal, 1987).
Least Recently Used Algorithm
The OS/2 makes use of the least recently used algorithm to swap out memory
segments when there is not enough physical memory space to allocate a program. This
is done by using a special bit in the descriptor table. This bit is either set or unset to
indicate if the memory segment that is trying to be accessed is memory resident or not.
When an application requests a memory segment that has been swapped out of main
memory a page fault occurs. The virtual memory manager then takes control and reads
the needed segment from the hard disk into physical memory. It then updates the
descriptor table to save the changes and the restarts the process that requested the
memory segment (Microsoft Systems Journal, 1987).
F. VIRTUAL MEMORY
On 32-bit OS/2 systems with 4-64 MiB physical memory I never got out of memory
errors. The reason is that OS/2 programs use virtual memory. And OS/2 had plenty of it
compared to my real memory resources which consisted of dynamic random-access
memory (DRAM) chips.
The 32 bit OS/2 versions 2.0-4.0 could address the whole 4 GiB (2^32) virtual
memory space of the Intel 386 processor: The first 512 MiB of the 4 GiB virtual address
space were available for 16 and 32 bit OS/2 user programs and the 3.5 GiB remainder
for the 32 bit kernel. So, OS/2 offered each program a generous amount of virtual
memory, when even only a fraction of it was physically available.
OS/2's virtual Memory Manager worked together with the MMU of the processor
to keep the needed virtual memory pages in physical memory (on demand paging). OS/2
imposed several “banker's” tricks to prevent the promised memory from being committed
too soon (lazy commit). Otherwise a 40 MiB hard disk would fill up easily.
Although an OS/2 programmer could write programs that used up to 480 MiB of
virtual memory (the upper 32 MiB of the 512 MiB were reserved for system DLLs), no
programmer would write such a program. 32-bit OS/2 programmers had worked with the

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16 MiB physical memory limit of 16-bit OS/2 v. 1.x. They knew that OS/2 customers had
in practice only 2-8 MiB RAM and did not possess fast and big enough hard disks to allow
for the needed paging file. Memory hungry programs would be terribly slow, and the
system would thrash (spend all its time swapping). Unlike Unix, OS/2 and MS Windows
were optimized for memory sharing between processes with minimal swapping. So,
programmers made use of the available PM, WPS, and other libraries, rather than re-
invent the wheel.
OS/2 virtual memory address schemes
G. SECONDARY STORAGE MANAGEMENT
Secondary storage is the non-volatile repository for (both user and system) data
and programs. As (integral or separate) part of an operating system, the file system
manages this information on secondary storage. Uses of secondary storage include
storing various forms of programs (source, object, executable) and temporary storage of
virtual memory pages (paging device or swap space). Information in secondary storage
may be in a variety of forms, including readable text and raw data (e.g., binary).
IBM OS/2 like other operating systems is responsible for secondary storage.
Usually comprising many hard-disk drives, but possibly also some solid-state NVRAM,

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secondary storage delivers high density and nonvolatility for long-term storage. The OS
may manage access to local disks for each node or a separate part of the system of disks
connected by a storage area network such as a redundant array of independent disks
configuration (there are several) for higher access bandwidth and greater reliability
through redundancy of storage. While secondary storage is important to users in its OS
support for file systems, it also provides other services. Virtual memory, in which pages
of data for a process may be temporarily stored in secondary storage, gives the
impression of larger memory capacity, although the data pages are actually distributed
between physical main memory and secondary storage. The OS also uses secondary
storage to buffer processes for future scheduling, or sometimes when swapping jobs in
and out of memory systems. In all these cases and more, the OS is responsible for
managing secondary storage, providing interfaces to it, and including services.
Secondary storage devices are non-volatile devices where the data is stored for
long-term storage. Disks are the mainly used secondary storage devices. They provide
the bulk of secondary storage in operating systems today.
The main activity that is performed in secondary storage management is disk
scheduling. There are many disk scheduling algorithms. However, the important ones are
FCFS scheduling, SSTF scheduling, SCAN scheduling and LOOK scheduling.

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H. NETWORKING AND CLOUD CAPABILITIES
International Business Machines Operating System 2 (IBM OS/2) offers the following
networking capabilities. On the other hand, Cloud Capabilities is not applicable.
• High Performance Routing (HPR) over WAN
• Branch Extender -- an APPN (R) Border Node subset
• Multi-link Transmission Group (MLTG) support
• Integrated Host On-Demand
• Remote Web-based administration
• New Windows NT and Windows 95 Access Feature support
• All the robust, function-rich capabilities included in Communications Server for
OS/2 Warp, Versions 4.0 and 4.1 and Communications Manager/2, such as:
• Complete multiprotocol support
• Complete Advanced Program-to-Program Network (APPN) node support
• 32-bit API support
• Connectivity
• LAN and WAN adapter support
• Superior performance over Microsoft SNA Server
IBM eNetwork Communications Server for OS/2 (R) Warp, Version 5.0 is part of
IBM's eNetwork Software family of communications servers. These servers provide
enterprise-class universal connectivity and information access for cost-effective network
computing.
Communications Server for OS/2 Warp, Version 5.0 enables PCs running OS/2,
Windows 3.1, Windows NT (TM), Windows (R) 95, and DOS to communicate with S/390
(R), AS/400 (R), and with each other, over SNA and TCP/IP networks. It supports token-
ring and Ethernet LANs, leased and switched lines, Frame Relay, FDDI, ISDN, SDLC,
GDLC, and X.25.
Communications Server provides a powerful multiprotocol communications
platform. You can mix SNA and TCP/IP-based networks as your networks evolve.
Applications written to either SNA, SOCKETS, IPX, or NetBios can execute unchanged

22
on mixed network backbones, providing enterprise-class end-to-end connectivity. It also
provides flexibility in adapting network support to your changing needs.
Communications Server for OS/2 Warp, Version 5.0 delivers enterprise-class
functionality, such as: HPR over WAN, Branch Extender, Host On-Demand, HPR MLTG
support, Remote Web-based administration, and Windows 95 and Windows NT access
feature support. Communications Server continues to deliver on its enterprise-class 3270
performance compared with Microsoft (R) SNA Server. It delivers superior transaction
throughput and faster response times, while requiring less CPU resources than SNA
Server. It provides:
• Enterprise-class reliability, scalability, and performance for mission-critical
environments
• End-to-end connectivity via versatile, high-capacity support for LAN-to-LAN, LAN-
to-host, and LAN-to-Internet via SNA, TCP/IP, IPX, and NetBios environments
• Ease-of-use via its remote Web-based administration and installation facilities

23
III. CONCLUSIONS
IBM OS/2, short for International Business Machines Operating Systems 2, is the
operating system of choice for thousands of users around the world in the late 1980’s
until 1990’s and early 2000’s. Yet, many people have never even heard of it.
Simply OS/2 is an operating system for PCs developed originally by Microsoft
Corporation and IBM but sold and managed solely by IBM. OS/2 is compatible with DOS
and Windows, which means that it can run all DOS and Windows programs. However,
programs written specifically to run under OS/2 will not run under DOS or Windows.
This operating system maybe obsoletes these days, other may not even
remembered what that is because of the rapid advancement of technology and the
emerging of different operating systems, but IBM OS/2 really contributed to how operating
systems nowadays handles computing tasks. Some key features that IBM OS/2 caters
include, but not limited to the following:
OS/2 included Adobe Type Manager for rendering Type 1 fonts on screen and
providing PostScript output on non-PostScript printers. OS/2's dual boot feature allowed
booting into OS/2 or DOS. The OS/2 Workplace Shell graphical user interface was similar
to Windows and Mac. Originally known as Presentation Manager (PM), after Version 2.0,
PM referred to the programming interface (API), not the GUI interface itself.
OS/2 is a very powerful operating system, supporting long filenames (using the
High Performance File System), the built-in REXX scripting language, Adobe Type
Manager and TrueType fonts, a 32-bit flat memory model, preemptive multitasking,
excellent networking and Internet support, multithreading, advanced multimedia including
software motion video, and robust communications, yet its Workplace Shell user interface
makes it remarkably easy to use and flexible. Other features include support for
technologies such as Java, OpenGL, ObjectREXX, NetREXX, and OpenDoc.
IBM OS/2 is without a doubt one of the backbones of today’s operating systems,
as it starts the emerging of Windows NT, which later developed other Windows operating
systems that are widely used today.

24
IV. REFERENCES
https://www.britannica.com/technology/IBM-OS-2
http://www.os2bbs.com/os2news/OS2History.html
https://winworldpc.com/product/os-2-warp-4/os-2-warp-40
https://www.computerhope.com/jargon/o/os2.htm
http://www.os2museum.com/wp/os2-history/os2-timeline/
https://www.operating-system.org/betriebssystem/_english/fa-ibm.htm
https://www.operating-system.org/betriebssystem/_english/bs-os2.htm
http://www.os2voice.org/VNL/past_issues/VNL0708H/feature_3.html
os2world.com – Community of OS/2 users
ecomstation.ru – Community of eComStation and OS/2 users
netlabs.org – OpenSource Software for OS/2 and eCS
hobbes.nmsu.edu – The OS/2 software repository
Matthew Nawrocki (26 February 2013). "Preview: eComStation 2.2 Beta, the legacy of
OS/2 lives on". TechRepublic.com. Retrieved 22 September 2013.
McCracken, Harry (April 2, 2012). "25 Years of IBM's OS/2: The Strange Days and
Surprising Afterlife of a Legendary Operating System". Time Magazine. Retrieved 20
May 2017.

25
V. APPENDIX
A. WORK PARTICIPATION OF THE MEMBERS
Leader:
• Insigne, Janssen Harvey P. – compiled every part of the analysis, researched for
the History and Development of IBM 0S/2, and its Secondary Storage
Management capabilities, and come up with the Conclusion is the last part.
Members:
• Evangelista, Luigi Miguel M. – researched for the Background of IBM OS/2, its
different Versions, Memory Management and Hardware ran by the operating
system.
• Magat, Ralph Gerard B. – researched for Networking and Cloud Capabilities of
IBM OS/2, and its Versions through the years.
• Medina, Jorge Ivan P. – researched for the CPU Allocation scheme of IBM OS/2,
and its Virtual Memory features.
• Rosales, Jhon Lelan C. – contributed in researching other timelines in the
development of the operating system.

IBM OS/2 Analysis

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