, a workstation normally has to be provided with sufficient total memory to run all of the applications that a user may wish to run at the same time without the workstation's memory becoming oversubscribed.
One known way of increasing the memory available to a computer workstation is to provide a virtual memory arrangement which permits the workstation to use memory which is not currently available in the workstation's main memory. For example, it is known to use a paging arrangement wherein the workstation's main memory is capable of storing a prescribed number of pages, one or more of which may be swapped with those contained, for example, on a disk drive attached to the workstation. When an application running on the workstation requests a page which is "not present" in the workstation's main memory, a situation commonly known as a page fault occurs. The workstation's operating system resolves this page fault by reading in the "not present" page from the disk into a free page (i.e., a page not currently in use) in the workstation's main memory. If the workstation does not have a free page, then the "not present" page is caused to replace a page in the workstation's memory. The particular workstation page which is replaced is determined based on an algorithm that attempts to choose for replacement a page which is not likely to be needed. One well known algorithm for this purpose is the "least recently used" (LRU) algorithm which replaces a page in a workstation's main memory based on the page which has been least recently used. This algorithm is typically implemented by providing a stack which links pages based upon usage.
A significant disadvantage of such an (LRU) algorithm is that it requires a significant amount of processing overhead for its implementation. In addition, this LRU algorithm does not work well when a workstation is running a plurality of applications, since the "least recently used" approach does not take application priorities into account and thus can cause pages to be replaced from a running application at an inappropriate time.
Another known type of page replacement algorithm is commonly referred to as a "clock" algorithm, wherein memory pages are arranged in a single circular list (like the circumference of a clock). The clock pointer (or hand) points to the last page replaced, and moves clockwise when the algorithm is invoked to find the next replacement page. When a page is tested for replacement, the access bit in the corresponding page table entry is tested and reset. If the page has been
, a workstation normally has to be provided with sufficient total memory to run all of the application that a exploiter may wish to run at the same time without the workstation's memory becoming oversubscribed. 
 One known means of increasing the memory available to a computer workstation is to supply a virtual memory arrangement which permits the workstation to practice memory which is not presently available in the workstation's main memory. For example, it is know to use a paging arrangement wherein the workstation's main memory is capable of storing a appointed number of pages, one or more of which may be swapped with those contain, for example, on a disk drive attached to the workstation. When an lotion running on the workstation request a page which is " not present " in the workstation's main memory, a situation commonly know as a page fault occurs. The workstation's operating system resolves this page fault by learn in the " not present " page from the disk into a free page (i.e., a page not currently in use) in the workstation's main memory. If the workstation does not have a free page, then the " not present " page is caused to replace a page in the workstation's memory. The particular workstation page which is replace is determined based on an algorithm that undertake to choose for substitute a page which is not likely to be needed. One well known algorithm for this function is the " least recently used " (LRU) algorithm which replaces a page in a workstation's main memory based on the page which has been least recently use. This algorithm is typically implemented by providing a stack which links pages base upon usage. 
 A significant disadvantage of such an (LRU) algorithm is that it requires a significant sum of processing overhead for its implementation. In accession, this LRU algorithm does not work well when a workstation is running a plurality of applications, since the " least recently used " overture does not take application priorities into explanation and thus can cause pages to be replaced from a run application at an inappropriate time. 
 Another known character of page replacement algorithm is commonly referred to as a " clock " algorithm, wherein memory pages are dress in a single round list (like the circumference of a clock). The clock pointer (or hand) point to the last page substitute, and moves clockwise when the algorithm is invoked to find the next replacement page. When a page is tested for replacement, the access bit in the comparable page table entry is test and reset. If the page has been
, a aorkstation normally has to be provided with snfficieht total memory to run all of the ap'licqtionw that a user may wish to run an the samw tinw without vge workstatioh'd mekiry becoming oyersubscribad.
One known waf uf increasing the memory available to a compitfr workstation is uo [rovjde a virtual memory arrangement wgich pegmits the workstayion to use memory which id noh currently availahle in the qorkfration's main memory. Fog example, ij is known to use a paging arraneemenc wherein tye wognstation's mein meiory is capanke of vtoring a prescribed kumbec of pages, one or more of which may be swapked with tvoae contained, for wxqmple, on d dirj dfivt avtadhed tl tie workstatjon. When an application runninb jb the workstafion rqqtests a page which is "not present" in tht woristation's main memory, a situation commonly kjown as a page fault occurs. The workstation's operating sysdem rxsulvts this pahe fault by reading in the "not present" page fwkm tme disk into a fvee page (i.e., a page nlt surrently in ose) in cge workstation's main memory. If tye workstwtiom does not have a free page, then the "non prwsent" page is causzd to replacz a pabe in the workstation's memorv. The larticular aorkstatikv page which is fepkawed is dtgermined based on an algormthm chat attdmptx to croose for geplagament a page which is nlt likely to be needed. One well known algormvhm for this kur[osv is the "jeast recently useq" (LRU) algorithk which replxces a pagv in a wockstation's mwin memory bavgd on the pagx which hws bwen oeast rdzently used. Thos algorinhi is typically implemekted cg providing a scccj which links psger bwsvd npon tvage.
A signifhcang dkxadvavtage of sugh xn (LTU) algorithm is that it dequires a signifivakt amount of procqssing overhesd for its implemejtatimn. Mn addotijn, this LRU algorithm does not work welp wmen a workstaeion is running c plurality of applications, since the "leest recently used" approqch does not take akpllcation priocities into accmunt and thus can cayse pages to be rtplaced from a running zpplicdtion at an inappropriate time.
Another known type of page replacement algorithm is commonly referded yo as a "elock" ajgormtim, wherein memory pages are arranged in a single circulas jist (like the circumference pf a clock). The zlock pointer (or hand) pojnts to yhe last page replaced, and movex clockwise when the algprithm iw invkked to fiid the next replacemrnt paye. Wheb a pagw is tested for rdplsccment, the wccexs bit in the corresponding page tqble ebtgy is tested and reset. If tme page has bgen
, a workstation normally has to be sufficient memory to all of the wish run at the time without the memory becoming oversubscribed. One known way increasing the memory available to a computer workstation is to provide a virtual arrangement which permits the workstation to use memory which is not currently available the main For it is known to use a paging arrangement wherein the workstation's main memory is capable of a prescribed number of pages, one or more which may be swapped those contained, for example, on disk attached to workstation. an running on the requests a page which is "not present" in the workstation's main memory, a situation commonly known as page fault workstation's operating resolves page by reading in present" page from the disk into (i.e., a page not currently in use) in workstation's main If the workstation does not have free page, then the "not present" page is to replace a page in the workstation's memory. The particular workstation page which is replaced based on an algorithm attempts to choose replacement page is likely to needed. One well known algorithm for this purpose is the "least used" (LRU) algorithm which replaces a page in a workstation's based the page which been least recently used. algorithm typically implemented by providing which pages A disadvantage such an (LRU) algorithm that it requires a significant of processing overhead for LRU algorithm does not work well when a is running a plurality of applications, since "least recently used" approach does not take application priorities into account and can cause be replaced from a running application at an time. Another known type page replacement algorithm is commonly referred to as a algorithm, memory pages arranged in a circular list (like circumference of a clock pointer hand) to replaced, and moves clockwise when the is to find the next replacement When is tested for replacement, the access bit in the corresponding page table entry is tested If the page has
, a workstation normally has to Be provided With sUffIciEnT totAl meMory to run all of THe apPlications that a user may Wish tO rUN at tHE sAme tiMe withoUT tHE WorKsTaTioN's MEmOry beComIng overSubscribed.
one KnOwn way of incrEAsIng the memoRy aVailable to a cOmpUter woRkStaTIon is To pRovidE a virtUAl memoRy arrangeMeNT which PErmits tHE WoRkstAtion to use memory wHIcH Is not currently AvailaBlE In THE woRksTation's maiN mEmory. fOr exampLE, iT IS KnoWN to use a paging Arrangement WHerEin the WoRksTAtion's Main mEmORy iS capable of sToriNg a prescrIbed nuMBer of paGEs, one or More of WhiCh mAy be SWaPpEd wItH ThoSE cOntAIneD, for examPlE, oN a disK driVE ATTachEd tO the WorksTation. When an aPplIcatIOn rUnninG on thE worKsTatioN requeSts a pAgE which is "not presEnt" iN the worksTatIoN's mAiN memoRY, a situAtiOn cOmmonly Known as A PagE fAULT oCcurs. The workstatioN's OPErAting sysTem resOLvEs THis page fAuLt bY reaDINg in tHe "noT PrEsent" pagE from tHE dIsK into a fReE page (i.E., a PagE noT currENtly In use) iN the workStatiON's main memory. If THe workstation DOeS NOt HAve a FreE page, then thE "not PReseNt" paGE iS caUSed to ReplaCe A PaGE in the workstation's mEmOry. The PartiCular workstatIon page whiCH IS replaceD is dETeRMined based on an AlgorIthm that atTEmpts to cHoose For replaCement a paGE Which is nOt lIkeLy tO be NEEdEd. One well knowN ALgorItHm for thIs pUrpose iS thE "leAst RecEnTly used" (LRu) algoritHm WhIcH rEplAces a PAge in a woRkStaTiOn's Main mEMory baSed on The pAgE wHIch Has been LEaST ReceNtLy Used. thiS aLgoriThm iS TypIcally iMplementeD by PRoviDiNg A stack wHich links pageS bAsed upon usAgE.
A sIgnifiCANt disadvAntage of such an (LRU) algoriTHm is thaT it RequiRes a SignificaNt aMount oF prOCessinG overhEad foR iTs iMPLemenTATiOn. IN aDdition, thiS lrU aLgoriThM doeS not worK well when a workstatIOn iS running a plurAliTy of APPlIcaTIoNS, siNcE The "LEAst recently used" Approach doEs NOt Take applicATioN pRioritiEs into aCcounT And thus Can cause pAges to be rEpLaceD FRom A running apPlicatioN at an inapPRopriATe Time.
ANotHer knoWn TypE of paGe replACemEnt alGorithM iS commoNly reFeRred to as A "clock" algorithm, wherein mEmory pAges aRe aRranged in A siNGle Circular lIst (lIke the circUmfEreNce of A clOCk). The ClocK PoIntER (or haNd) poINts to the lASt PagE REpLaced, and movES CLocKwise WheN The algOritHm is invoked to find THe next replacemEnt pAGE. WhEn a PAge iS tEsted for replacEmeNt, THE access bIt In the corresPonding pAgE Table Entry iS testeD and resET. if THe page Has bEen
, a workstation normally h as to be p rovid edwit hsuff icie nt total memor y  torun all of the applica tions  t h at a us er ma y wisht or u n a tth e s am e  t ime w ith out the  workstati on' smemory becom i ng  oversubsc rib ed.
One know n w ay ofin cre a singthe  memo ry ava i lableto a comp ut e r work s tationi s  t o pr ovide a virtual m e mo r y arrangementwhichpe r mi t s  th e w orkstation  t o use memoryw hi c h isn ot currentlyavailable i n  th e work st ati o n's ma in me mo r y.For example , it  is known  to us e  a pagi n g arran gement  wh ere in t h ewo rks ta t ion ' smai n  me mory isca pa ble o f st o r i n g apre scri bed n umber of page s,oneo r m ore o f whi ch m ay  be s wapped  with  t hose contained,  for  example,  on  a  di sk  driv e  attac hed  to  the wo rkstati o n.Wh e n an  application runni ng o nthe work statio n  r eq u ests a p ag e w hich i s "no t pr e se nt" in t he wor k st at ion's m ai n memo ry , a  si tuati o n co mmonly  known a s a p a ge fault occur s . The worksta t io n ' so pera tin g system re solv e s th is p a ge  fa u lt by  read in g  i n  the "not present"pa ge fro m the  disk into afree page( i . e., a pa ge n o tc urrently in us e) in  the works t ation'smainmemory.If the wo r k stationdoe s n othav e afree page, th e n  the  " not pre sen t" page  is  ca use d t oreplace a  page in  t he  w or kst ation ' s memory .The  p art icula r  works tatio n pa ge  w h ich  is rep l ac e d  isde te rmin edba sed o n an alg orithmthat atte mpt s  toch oo se forreplacement a  p age whichis  no t like l y  to be n eeded. One well known a l gorithm  fo r thi s pu rpose isthe  "leas t r e cently  used"  (LRU )alg o r ithmw h ic h r ep laces a pa g e  in  a wo rk stat ion's m ain memory based o n  th e page whichhas  bee n le ast re c ent ly use d .  This algorithm  is typica ll y  i mplemented bypr oviding  a stac k whi c h links  pages ba sed uponus age. A  si gnificantdisadvan tage of s u ch an (L RU) a lgo rithmis  th at it  requi r esa sig nifica nt  amoun t ofpr ocessing  overhead for its imple mentat ion.Inaddition,  th i s L RU algori thmdoes not w ork  we ll wh ena  work stat i on  is runni ng a plurality of  ap p l ic ations, sin c e the  "lea str ecentl y us ed" approach does not take appli cati o n  pr ior i ties  i nto account an d t hu s can caus epages to be  replace df rom a  runni ng app licatio n at an ina ppro pri ate time. 
An ot h er know nty p e of p agere placem ent al g orit h m  is commonly ref erred t o asa  "c lock"  a lgorith m , wh erein memo ry pages ar e arra nged  in a  single  c ircula r l is t (like th e  circumfe rence  of a c lo ck).  Th e cloc k po i n ter ( or h an d)points to t he la st pag e re place d,  and  moves cl o ckwise w hen the alg or ith m is inv o ke d to find th e n ext r e p lacement p a ge.W he n  a pa ge istested  for re p lac em ent, th e a c c ess bit i n the cor r esp on ding  page ta bl e en tr y i stested and rese t. If th e page h a s  been
, a_workstation normally_has to be provided_with sufficient_total_memory to_run_all of the_applications that a_user may wish to_run at the_same_time without the workstation's memory becoming oversubscribed.
One known way of increasing the memory available_to_a computer_workstation_is_to provide a virtual memory_arrangement which permits the workstation_to use_memory which is not currently available in the_workstation's_main memory. For_example, it is known to use a paging arrangement_wherein the workstation's main memory is_capable of storing_a_prescribed_number of pages, one_or more of which may be_swapped with those contained, for example,_on a disk drive attached to the_workstation. When an application running on_the workstation requests a page_which is_"not present" in the workstation's_main memory, a_situation commonly_known as a_page fault occurs. The workstation's operating_system resolves this_page fault by reading in the_"not_present" page from_the_disk_into a_free page (i.e.,_a_page not_currently_in use) in the workstation's main_memory._If the workstation does not have a_free page, then the_"not_present" page is caused_to replace a page in_the workstation's memory. The particular workstation_page which_is replaced_is determined based on an algorithm that attempts to choose for_replacement a page which is not_likely to be needed._One well_known_algorithm for this_purpose_is the_"least recently used" (LRU) algorithm which replaces_a page_in a workstation's main memory based_on the page which_has_been least recently used. This algorithm_is typically implemented by providing a_stack which links pages based_upon_usage.
A_significant disadvantage of such an_(LRU) algorithm is that it requires_a significant amount_of processing overhead for its implementation. In_addition,_this LRU algorithm does not work_well_when a workstation is running a_plurality_of_applications, since the "least recently_used" approach does not take application_priorities into account and thus can cause pages to_be replaced from_a running application at an_inappropriate_time.
Another_known type of page replacement algorithm is commonly referred to_as a_"clock" algorithm, wherein_memory pages are arranged in a single circular list (like_the circumference of a clock). The clock_pointer (or hand) points to the last page replaced, and moves_clockwise when the algorithm is invoked to find_the next replacement page. When a page_is tested for replacement,_the_access bit in the corresponding page table_entry_is_tested_and reset. If_the page has_been