OS/2 FAQ List: User's Edition (4 Apr 94)

(1.1) What is OS/2?

What is OS/2?

OS/2 is an advanced operating system for PCs with an 80286 processor or 
better.  It was codeveloped by Microsoft and IBM and envisioned as the 
successor to DOS.

It was designed from the ground up with preemptive multitasking and 
multithreading in mind.  "Preemptive multitasking" means that the 
operating system is responsible for allocating processor time to the one 
or more applications which are running.  (Cooperative multitasking, as 
found in Microsoft Windows or the Macintosh's System 7, requires that each 
application surrender the processor after a certain amount of time.  If 
one application refuses to yield, all the other applications stop 
running.)  "Multithreading" means that programs can start subtasks which 
will then be executed by the operating system in the background.  For 
example, a word processor may create a separate thread (subtask) to handle 
printing or saving to disk.  When the user asks the word processor to 
perform one of these tasks, the word processor creates a new thread and 
control returns to the word processor (and the user) immediately.  The 
subtask is executed by the operating system in the background.  The user 
is then free to ask the word processor to perform another task without 
waiting for the thread to complete.  Applications which utilitize 
multithreading can be much more responsive to the user.

OS/2 also protects applications from one another (a single misbehaved 
program will not typically disrupt the entire system), supports all 
addressable physical RAM, and supplies virtual memory to applications as 
requested, breaking DOS's 640K barrier.

An OS/2 demonstration diskette (which will run on any PC with VGA or 
better, and DOS or OS/2) is available from IBM by calling (800) 3-IBM-OS2. 
 The OS/2 2.1 demo diskette may also be downloaded; see (3.2) Shareware 
and Freeware Sources.

Related information:

(1.2)  Differences Between Versions 
(1.3)  DOS and Windows Compatibility 
(3.2)  Shareware and Freeware Sources 
(3.10) Extended Services

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