Browse Definitions:
Definition

DOS Protected Mode Interface (DPMI)

Contributor(s): Alain Steffes

DPMI (DOS Protected Mode Interface) is a program interface that allows an application program running under the Disk Operating System (DOS) to take advantage of a DOS extender , which lets the program address a larger range of random access memory ( RAM ) than the 640 kilobytes to which PC programs are basically constrained. To use the extender, the program must be in "protected mode," a mode that ensures that program requests are not allowed to access certain portions of "protected" memory. (Programs running in the alternative "real mode" have access to all portions of memory, including system data.)

The first widely-distributed operating system for personal computers, DOS was designed to run on the Intel 8088 microprocessor . The 8088 provided a megabyte of RAM that could be addressed by a program instruction (that is, the total span of storage for storing and getting data back and forth between the microprocessor and RAM was a million bytes). Because certain space had to be reserved for "system" use (keeping track of applications, system status, and so forth), only 640 kilobytes was available for an application program. These bytes were contiguous in storage (that is, continuously adjacent to each other and not divided into different parts of RAM) and application programs were required to run and keep their data within this 640 kilobyte space. In fact, an instruction that violated the 640 kilobyte space would not be executed (thus protecting the system space in RAM). A program that ran in "real mode" could address the entire 1 megabyte of RAM including system data, but at the risk of writing data to the wrong place.

As new microprocessors such as the 80286 followed the 8088, DOS continued to preserve the 640 kilobyte addressing limitation so that newly-written application programs could continue to run on both the old as well as new microprocessors. The DOS extender program allowed application programs written for DOS to be freed from the 640K constraint by inserting memory management code into the application. Microsoft developed the DPMI for use on Windows 3.0 (which was itself a DOS application) and later gave the standard to an industry organization, the DPMI Committee.

Today's personal computers, using microprocessors that succeeded the 8088, typically contain eight or more megabytes of RAM. Today's operating systems (including the latest DOS versions) come with extended memory management that frees the programmer from the original addressing constraints.

Besides the DPMI standard interface, two other standard extended memory management interfaces exist. Extended Memory Specification (XMS) is a program added to more recent versions of DOS and Windows when the system is loaded. It's called HIMEM.SYS. Another extended memory manager is the Virtual Control Program Interface (VCPI).

This was last updated in March 2011

Start the conversation

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

-ADS BY GOOGLE

File Extensions and File Formats

Powered by:

SearchCompliance

  • PCAOB (Public Company Accounting Oversight Board)

    The Public Company Accounting Oversight Board (PCAOB) is a Congressionally-established nonprofit that assesses audits of public ...

  • cyborg anthropologist

    A cyborg anthropologist is an individual who studies the interaction between humans and technology, observing how technology can ...

  • RegTech

    RegTech, or regulatory technology, is a term used to describe technology that is used to help streamline the process of ...

SearchSecurity

  • Advanced Encryption Standard (AES)

    The Advanced Encryption Standard, or AES, is a symmetric block cipher used by the U.S. government to protect classified ...

  • identity theft

    Identity theft, also known as identity fraud, is a crime in which an imposter obtains key pieces of personally identifiable ...

  • spear phishing

    Spear phishing is an email-spoofing attack that targets a specific organization or individual, seeking unauthorized access to ...

SearchHealthIT

SearchDisasterRecovery

  • call tree

    A call tree -- sometimes referred to as a phone tree -- is a telecommunications chain for notifying specific individuals of an ...

  • mass notification system (MNS)

    A mass notification system is a platform that sends one-way messages to inform employees and the public of an emergency.

  • disaster recovery as a service (DRaaS)

    One approach to a strong disaster recovery plan is DRaaS, where companies offload data replication and restoration ...

SearchStorage

  • CIFS (Common Internet File System)

    CIFS (Common Internet File System) is a protocol that gained popularity around the year 2000, as vendors worked to establish an ...

  • GlusterFS (Gluster File System)

    GlusterFS (Gluster File System) is an open source distributed file system that can scale out in building-block fashion to store ...

  • virtual memory

    Virtual memory is a memory management capability of an OS that allows a computer to compensate for physical memory shortages by ...

SearchSolidStateStorage

  • Tier 0

    Tier 0 (tier zero) is a level of data storage that is faster, and perhaps more expensive, than any other level in the storage ...

  • PCIe SSD (PCIe solid-state drive)

    A PCIe SSD (PCIe solid-state drive) is a high-speed expansion card that attaches a computer to its peripherals.

  • SSD caching

    SSD caching, also known as flash caching, is the temporary storage of data on NAND flash memory chips in a solid-state drive so ...

SearchCloudStorage

  • RESTful API

    A RESTful application program interface breaks down a transaction to create a series of small modules, each of which addresses an...

  • cloud storage infrastructure

    Cloud storage infrastructure is the hardware and software framework that supports the computing requirements of a private or ...

  • Zadara VPSA and ZIOS

    Zadara Storage provides block, file or object storage with varying levels of compute and capacity through its ZIOS and VPSA ...

Close