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DEFINING YOUR OWN NLQ CHARACTERS
As youprobablynoticed,NLQcharactersareprintedbytwo passesofthe
printhead.Halfofthecharacterisprintedonthefirstpass,andtheremainder
onthesecondpass.Thepaperisrolleduphalfadotheightinbetweenpasses
to lettheprintheadprintdotson thesecondpassthatoverlaptheprevious
dots,in orderto fill in thespacesandproducedensercharacters.Addition-
ally,theprinthead speedis halved,andthedotsare printedat doublethe
densityof draftcharacters.Forthisreason,NLQcharacterscan containup
to 23 dotsin the horizontaldirection.
Fundamentally,theprocessto defineandprintdownloadedNLQcharacter
is the sameas for draftcharacters,exceptthatyoumustsupplyaboutfour
timesasmuchcharacterdata,andyoumustdesignthecharacterwiththetwo
passesof theprintheadinmind.Thereamsmalldifferencesin thewaythe
attributeinformationis processedalso.
In the draftqualitymodethe attributebytecarriesthedescenderdata,and
specifiestheleft spaceandthecharacterwidth.In theNLQmode,thefirst
bit also carries the descenderdata, and the next three bits describethe
character’sleft space as with the draft characters,but the last four bits
describethe rightspace.Appropriateallocationof datain thesesevenbits
lets you place the character where you like within the grid, with the
restrictionthatthecharactermustbe atleast9 dotswide.
UsethegridinFigure5-4tohelpplotthedata.Duetothetwo-passprocess,
NLQcharacterscancontainupto 16dotsvertically.ml tom23arethedata
forthe firstpass,andm24to m46arethe datafor the secondpass.
To makethecharacterdataeasierto calculate,putthefirstpassdotsinside
theboxesonthegridwhenyouaredesigningyourcharacters,andthesecond
passdotsonthelines.Rememberthatadjacentdotsmaynotoverlapon the
samepass;in otherwords,if onedotisin abox,its adjacentdotonthesame
passmaynotbeonaline.Therefore,tomakesmoothcharacters,putthedots
neededto overlapanyspacesin a characterintheappropriateplacesin the
secondpass grid.
Ifweplotourcar-shapedsymbolforNLQ,thegriddatawilllooklikeFigure
5-5.
Thedefiningprocessisthesameasfordraftcharacters,exceptthatyoumust
selectNLQ mode,and youmustdefine46 data.If youwish to printyour
NLQ characterswith the regularcharacterset, the remarksregardingthe
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