Encyclopedia of Computer Science and Technology

60 bufferingKismet, a robot that includes dynamically changing “emotions.”Brooks’s student Cynthia Breazeal would build herown research career on Kismet and what she calls “sociablerobots” (see Breazeal, Cynthia).By 1990, Brooks wanted to apply his ideas of behaviorbasedrobotics to building marketable robots that couldperform basic but useful tasks, and he enlisted two of hismost innovative and hard-working students, Colin Angleand Helen Greiner (see iRobot Corporation). The companyis best known for the Roomba robotic vacuum cleaner.Brooks remains the company’s chief technical officer.Meanwhile Brooks has an assured place as one of thekey innovators in modern robotics research. He is a FoundingFellow of the American Association for Artificial Intelligenceand a Fellow of the American Association for theAdvancement of Science. Brooks received the 1991 Computersand Thought Award of the International Joint Conferenceon Artificial Intelligence. He has participated innumerous distinguished lecture series and has served as aneditor for many important journals in the field, includingthe International Journal of Computer Vision.Further ReadingBrockman, John. “Beyond Computation.” Edge 2000. Availableonline. URL: http://www.edge.org/3rd_culture/brooks_beyond/beyond_index.html. Accessed May 3, 2007.———. “The Deep Question: A Talk with Rodney Brooks.” Edge29 (November 19, 1997). Available online. URL: http://www.edge.org/documents/archive/edge29.html. Accessed May 3,2007.Brooks, Rodney. Flesh and Machines: How Robots Will Change Us.New York: Pantheon Books, 2002.Computer Science and Artificial Intelligence Laboratory (CSAIL),MIT. Available online. URL: http://www.csail.mit.edu/index.php. Accessed May 3, 2007.Henderson, Harry. Modern Robotics: Building Versatile Machines.New York: Chelsea House, 2006.O’Connell, Sanjida. “Cog—Is It More than a Machine?” LondonTimes (May 6, 2002): 10. Rodney Brooks [homepage]. CSAIL.Available online. URL: http://people.csail.mit.edu/brooks/.Accessed May 3, 2007.“Rodney Brooks—The Past and Future of Behavior Based Robotics”[Podcast]. Available online. URL: http://lis.epfl.ch/resources/podcast/mp3/TalkingRobots-RodneyBrooks.mp3.Accessed May 3, 2007.bufferingComputer designers must deal with the way different partsof a computer system process data at different speeds. Forexample, text or graphical data can be stored in main memory(RAM) much more quickly than it can be sent to aprinter, and in turn data can be sent to the printer fasterthan the printer is able to print the data. The solution tothis problem is the use of a buffer (sometimes called aspool), or memory area set aside for the temporary storageof data. Buffers are also typically used to store data to bedisplayed (video buffer), to collect data to be transmittedto (or received from) a modem, for transmitting audio orvideo content (see streaming) and for many other devices(see input/output). Buffers can also be used for data thatmust be reorganized in some way before it can be furtherprocessed. For example, character data is stored in a communicationsbuffer so it can be serialized for transmission.Buffering TechniquesThe two common arrangements for buffering data are thepooled buffer and the circular buffer. In the pool buffer,multiple buffers are allocated, with the buffer size beingequal to the size of one data record. As each data record isreceived, it is copied to a free buffer from the pool. When itis time to remove data from the buffer for processing, datais read from the buffers in the order in which it had beenstored (first in, first out, or FIFO). As a buffer is read, it ismarked as free so it can be used for more incoming data.In the circular buffer there is only a single buffer, largeenough to hold a number of data records. The buffer is setup as a queue (see queue) to which incoming data recordsare written and from which they are read as needed for processing.Because the queue is circular, there is no “first” or“last” record. Rather, two pointers (called In and Out) aremaintained. As data is stored in the buffer, the In pointer isincremented. As data is read back from the buffer, the Outpointer is incremented. If either pointer reaches aroundback to the beginning, it begins to wrap around. The softwaremanaging the buffer must make sure that if the Inpointer goes past the Out pointer, then the Out pointermust not go past In. Similarly, if Out goes past In, then Inmust not go past Out.The fact that programmers sometimes fail to check forbuffer overflows has resulted in a seemingly endless seriesof security vulnerabilities, such as in earlier versions of theUNIX sendmail program. In one technique, attackers canuse a too-long value to write data, or worse, commandsinto the areas that control the program’s execution, possiblytaking over the program (see also computer crime andsecurity).Buffering is conceptually related to a variety of othertechniques for managing data. A disk cache is essentially aspecial buffer that stores additional data read from a disk inanticipation that the consuming program may soon requestit. A processor cache stores instructions and data in anticipationof the needs of the CPU. Streaming of multimedia(video or sound) buffers a portion of the content so it can beplayed smoothly while additional content is being receivedfrom the source.Depending on the application, the buffer can be a partof the system’s main memory (RAM) or it can be a separatememory chip or chips onboard the printer or other device.Decreasing prices for RAM have led to increases in thetypical size of buffers. Moving data from main memoryto a peripheral buffer also facilitates the multitasking featurefound in most modern operating systems, by allowingapplications to buffer their output and continue processing.Further ReadingBuffer Overflow [articles]. Available online. URL: http://doc.bughunter.net/buffer-overflow/.Accessed May 23, 2007.Grover, Sandeep. “Buffer Overflow Attacks and Their Countermeasures.”Linux Journal, March 3, 2003. Available online.URL: http://www.linuxjournal.com/article/6701. AccessedMay 23, 2007.