▁provided ▁the ▁ 8 ▁digits ▁of ▁accuracy ▁that ▁were ▁accepted ▁as ▁the ▁minimum ▁requirement . ▁ ▁Since ▁memory ▁and ▁storage ▁space ▁and ▁costs ▁drove ▁the ▁system , ▁going ▁to ▁ 6 4 ▁bits ▁was ▁simply ▁not ▁acceptable ▁in ▁general . ▁These ▁systems ▁use ▁ones ' ▁complement ▁arithmetic , ▁which ▁was ▁not ▁unusual ▁at ▁the ▁time . ▁Al most ▁all ▁computer ▁manufact ur ers ▁of ▁the ▁time ▁delivered ▁ 3 6 - bit ▁systems ▁with ▁ 6 - bit ▁characters ▁including ▁IBM , ▁DE C , ▁General ▁Electric , ▁and ▁S ylvan ia . ▁ ▁The ▁ 6 - bit ▁character ▁set ▁used ▁by ▁the ▁ 1 1 0 0 ▁Series ▁is ▁also ▁a ▁Do D ▁mand ated ▁set . ▁ ▁It ▁was ▁defined ▁by ▁the ▁Army ▁Sign al ▁Corps ▁and ▁called ▁Field ata ▁( data ▁returned ▁from ▁the ▁field ). ▁ ▁The ▁ 1 1 0 8 ▁provided ▁a ▁ 9 - bit ▁character ▁format ▁in ▁order ▁to ▁support ▁ASCII ▁and ▁later ▁the ▁ISO ▁ 8 - bit ▁sets , ▁but ▁they ▁were ▁not ▁extens ively ▁used ▁until ▁the ▁ 1 9 8 0 s ▁again ▁because ▁of ▁space ▁constraints . ▁ ▁The ▁ 2 2 0 0 ▁Series ▁architecture ▁provides ▁many ▁registers . ▁ ▁Base ▁registers ▁log ically ▁contain ▁a ▁virtual ▁address ▁that ▁points ▁to ▁a ▁word ▁in ▁a ▁code ▁or ▁data ▁bank ▁( segment ). ▁ ▁They ▁may ▁point ▁to ▁the ▁beginning ▁of ▁the ▁bank ▁or ▁to ▁any ▁word ▁within ▁the ▁bank . ▁ ▁Index ▁registers ▁are ▁used ▁by ▁instructions ▁to