The PC speaker is the most primitive sound system used in IBM compatible PCs, and in fact used to be the only one in use in PC games before more technologically advanced sound cards such as AdLib or the Sound Blaster were introduced as ISA plug-in cards in the late 1980s. However, even some years after these sound cards became mainstream and widely used, game manufacturers continued to support PC-speaker-only sound/music in their games in order to maximise their customer base. This was in part due to the fact that sound cards did not originally follow any commonly agreed-upon standard and were largely incompatible with each other, whereas the PC speaker was the only sound system that could be regarded as universally present. One of the first PCs from IBM - the IBM PC model 5150. ... A sound card based on VIA Envy chip A sound card is a computer expansion card that can input and output sound under program control. ... AdLib, Inc. ... The Sound Blaster family of sound cards was for many years the de facto standard for audio on the IBM PC compatible system platform, before PC audio became commoditized, and backward-compatibility became less of a feature. ... Industry Standard Architecture (in practice almost always shortened to ISA) is a computer bus standard for IBM compatibles. ...

The PC speaker is best characterized by its inability to play more than one tone at once. Because of this, it was often nicknamed a PC beeper or PC squeaker, especially when sound cards became widely available. In spite of its limited nature, the PC speaker was often used in very innovative ways to create the impression of polyphonic music or sound effects within computer games of its era, such as the LucasArts series of adventure games from the mid-1990s, using swift arpeggios. Several programs, including MP (Module Player, 1989), ScreamTracker, Impulse Tracker, and even a Microsoft Windows device driver, could play PCM sound through the PC speaker using special techniques explained later in this article. However, because the method used to reproduce PCM was very sensitive to timing issues, these effects either caused noticeable sluggishness on slower PCs, or sometimes failed completely on faster PCs (that is, significantly faster than the program was originally developed for). Polyphony is a musical texture consisting of several independent melodic voices, as opposed to music with just one voice (monophony) or music with one dominant melodic voice accompanied by chords (homophony). ... LucasArts Entertainment Company is a video game developer and publisher. ... This article will be merged with Italian musical terms at some point in the near future. ... ScreamTracker is a versatile multi-track digital sequencer created by members of Finlands Future Crew (FC), legendary in the PC demo scene. ... Impulse Tracker 2. ... Microsoft Windows is a series of operating environments and operating systems created by Microsoft for use on personal computers and servers. ... PCM is an initialism which can have different meanings: Phase Change Material Pulse-code modulation, a way to digitally encode signals representing sound and their video counterparts Potential Cancer Marker Communist Party of Mexico Plug Compatible Manufacturer Power-train control module, a computer in a car which controls the car...

All modern operating systems include a generic sound API, so that applications no longer need to know the specifics of each sound card. Correspondingly, the use of high-quality sound hardware has become commonplace. As a result, the PC speaker today deals mainly with low-level warning signals such as start-up errors -- though it can still be used to its full potential should the need arise (as long as it hasn't been reduced to an onboard miniature piezo speaker, whose acoustic properties are so different from the paper cone speakers of old that most of the usual "tricks" don't sound nearly right). In computing, an operating system (OS) is the system software responsible for the direct control and management of hardware and basic system operations. ... API may refer to: In computing, application programming interface In petroleum industry, American Petroleum Institute In education, Academic Performance Index This page concerning a three-letter acronym or abbreviation is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Piezoelectricity is the ability of certain crystals to generate a voltage in response to applied mechanical stress. ...

The PC speaker is normally meant to provide only 2 levels of output (ie. 1-bit sound), through writing to the least significant bit of PC I/O port 61H (61 hexadecimal). However, by carefully timing a short pulse (ie. going from one output level to the other and then back to the first), it is possible to drive the speaker to various output levels in between the two defined levels. This effectively allows the speaker to function as a crude DAC, thereby enabling playback of PCM audio. However, the precision of this technique is limited to about 6 bits, and final audio results will depend on precise timing, internal hardware noise, CPU activity, and the exact method used to produce the source audio data. This technique will also not work on modern machines, particularly laptops, that use a piezo speaker. This article is about the unit of information. ... In computing, the least significant bit (LSB) is the bit position in a binary number having the value of 1. ... In computing, a port (derived from seaport) is usually a connection through which data is sent and received. ... In mathematics and computer science, hexadecimal, or simply hex, is a numeral system with a radix or base of 16 usually written using the symbols 0–9 and A–F or a–f. ... In signal processing, the term pulse has the following meanings: A rapid, transient change in the amplitude of a signal from a baseline value to a higher or lower value, followed by a rapid return to the baseline value. ... In electronics, a digital-to-analog converter (DAC or D-to-A) is a device for converting a digital (usually binary) code to an analog signal (current, voltage or charges). ... Laptop with touchpad. ...

On some hardware implementations, the same I/O port can be read, providing not only status information but also a rough "recording" of the PC speaker's output or a sort of "white noise" if nothing is being played back at the moment, making for a limited use as a random number generator. Four thousandths of a second of white noise White noise ( ▶ (help· info)) is a random signal (or process) with a flat power spectral density. ... A random number generator is a computational or physical device designed to generate a sequence of numbers that does not have any easily discernable pattern, so that the sequence can be treated as being random. ...

External links

• GameDev.net article on programming the PC Speaker.
• Part 1 of another article about programming the PC speaker.
• Part 2 of the article
  (includes a very detailed explanation of how to playback PCM audio on the PC speaker, and why it works)