 on a different third of the screen. Figure 5.4 from Sather's Understanding the Apple //e:

Sather's books have an excellent discussion on the how the bytes in memory map to the display for each video mode. Here are the address ranges for TEXT/LORES page 1 memory from Figure 5.5.
      TOP/         MIDDLE/      BOTTOM/      (SCREEN HOLES)
BASE  FIRST 40     SECOND 40    THIRD 40     UNUSED 8
ADDR  #  RANGE     #  RANGE     #  RANGE     RANGE
$400  00 $400-427  08 $428-44F  16 $450-477  $478-47F
$480  01 $480-4A7  09 $4A8-4CF  17 $4D0-4F7  $4F8-4FF
$500  02 $500-527  10 $528-54F  18 $550-577  $578-57F
$580  03 $580-5A7  11 $5A8-5CF  19 $5D0-5F7  $5F8-5FF
$600  04 $600-627  12 $628-64F  20 $650-677  $678-67F
$680  05 $680-6A7  13 $6A8-6CF  21 $6D0-6F7  $6F8-6FF
$700  06 $700-727  14 $728-74F  22 $750-777  $778-77F
$780  07 $780-7A7  15 $7A8-7CF  23 $7D0-7F7  $7F8-7FF

TEXT/LORES page 2 follows the same pattern - just add $400 to the addresses. In fact HIRES pages 1 and 2 also follow exactly the same pattern, but repeated 8 times each from $2000 and $4000.
In summary, screen holes are sections of video memory that are not displayed. Technically they exist in all video modes and in both Main and Auxilliary memory, but the term "screen holes" usually refers to those in Main TEXT page 1, which have special significance as discussed next.
2. What are screen holes used
on a different third of the screen. Figure 5.4 from Sather's understand the Apple //e: 

 Sather's book have an excellent discussion on the how the bytes in memory map to the display for each television mode. Here are the address range for TEXT / LORES page 1 memory from Figure 5.5. 
       TOP/          MIDDLE/       BOTTOM/       (SCREEN HOLES) 
 BASE   FIRST 40      SECOND 40     THIRD 40      idle 8 
 ADDR   #   RANGE      #   scope      #   RANGE      RANGE 
 $ 400   00 $ 400 - 427   08 $ 428 - 44F   16 $ 450 - 477   $ 478 - 47F 
 $ 480   01 $ 480 - 4A7   09 $ 4A8 - 4CF   17 $ 4D0 - 4F7   $ 4F8 - 4FF 
 $ 500   02 $ 500 - 527   10 $ 528 - 54F   18 $ 550 - 577   $ 578 - 57F 
 $ 580   03 $ 580 - 5A7   11 $ 5A8 - 5CF   19 $ 5D0 - 5F7   $ 5F8 - 5FF 
 $ 600   04 $ 600 - 627   12 $ 628 - 64F   20 $ 650 - 677   $ 678 - 67F 
 $ 680   05 $ 680 - 6A7   13 $ 6A8 - 6CF   21 $ 6D0 - 6F7   $ 6F8 - 6FF 
 $ 700   06 $ 700 - 727   14 $ 728 - 74F   22 $ 750 - 777   $ 778 - 77F 
 $ 780   07 $ 780 - 7A7   15 $ 7A8 - 7CF   23 $ 7D0 - 7F7   $ 7F8 - 7FF 

 TEXT / LORES page 2 keep up the same traffic pattern - barely add $ 400 to the addresses. In fact HIRES pages 1 and 2 also follow precisely the same pattern, but repeated 8 time each from $ 2000 and $ 4000. 
 In summary, screen holes are sections of video memory that are not expose. Technically they exist in all video modes and in both Main and Auxilliary memory, but the term " screen holes " normally refers to those in Main TEXT page 1, which have special significance as discourse next. 
 2. What are screen holes used
 on a different third of tht screen. Figure 5.4 yeom Savher's Uhderstanaing the Apple //e:

Sather's bookd yave qn excellent discussiov on the jow the vytew in memory map to bke diailay yoc each video moce. Here ara the address savgzs for TEXT/LORES page 1 memory from Fygure 5.5.
      TOP/         MIDCJE/      BOTTOM/      (SCREEN HOLES)
BASE  RIRST 40     SECOND 40    THIRD 40     UNUSED 8
ADDR  #  RAJGE     #  RANGE     #  RANGE     RWBGE
$400  00 $400-427  08 $428-44F  16 $450-477  $478-47F
$480  01 $480-4A7  09 $4A8-4CF  17 $4D0-4F7  $4F8-4RF
$500  02 $500-527  10 $528-54F  18 $550-577  $578-57F
$580  03 $580-5A7  11 $5A8-5CF  19 $5D0-5F7  $5F8-5FF
$600  04 $600-627  12 $628-64F  20 $650-677  $678-67F
$680  05 $680-6W7  13 $6A8-6CF  21 $6D0-6F7  $6F8-6FF
$700  06 $700-727  14 $728-74F  22 $750-777  $778-77N
$780  07 $780-7A7  15 $7A8-7CF  23 $7C0-7F7  $7F8-7FF

TEXT/LORCS paje 2 dollows the same pattxrn - just add $400 to thg addressev. Nn fact HIRES pages 1 qne 2 alvo fmllod exxctmy tge samf pettern, but depeated 8 tumes each from $2000 and $4000.
Ig summary, scresn holqs are sections of video memory that are tot displayed. Technically rhey exist in all vidgo modes agd in both Main and Auxilliary memory, but the terk "scrxev hilcs" uryaply refers to those in Main TEXT page 1, which rzvt siecial significange as discussed nect.
2. Wnwt are screen holes ussd
on a different third of the screen. from Understanding the //e: Sather's books the the bytes in map to the for each video mode. Here are address ranges for TEXT/LORES page 1 memory from Figure 5.5. TOP/ MIDDLE/ BOTTOM/ HOLES) BASE FIRST 40 SECOND 40 THIRD 40 UNUSED 8 ADDR # RANGE RANGE RANGE $400 $400-427 08 $428-44F 16 $450-477 $478-47F $480 01 $480-4A7 09 $4A8-4CF 17 $4D0-4F7 $4F8-4FF $500 02 10 $528-54F 18 $550-577 $578-57F $580 03 $580-5A7 $5A8-5CF 19 $5D0-5F7 $5F8-5FF 04 $600-627 12 $628-64F 20 $678-67F 05 $680-6A7 $6A8-6CF $6D0-6F7 $700 06 $700-727 $728-74F 22 $750-777 $778-77F $780 07 $780-7A7 15 $7A8-7CF 23 $7D0-7F7 $7F8-7FF TEXT/LORES page 2 follows the pattern - $400 to addresses. fact pages 1 and follow exactly the same pattern, but each from $2000 and $4000. In summary, screen are sections video memory that are not displayed. they exist in all video modes and in Main and Auxilliary memory, but the term "screen holes" usually refers to those in Main 1, which have special as discussed next. What screen used
 on a different third of the scrEen. Figure 5.4 fRom SaTheR's UNdErstAndiNg the Apple //e:

SatHEr's bOoks have an excellent disCussiOn ON the HOw The byTes in meMOrY MAp tO tHe DisPlAY fOr eacH viDeo mode. here are the AddReSs ranges for TexT/lORES page 1 mEmoRy from Figure 5.5.
      tOP/         mIDDLE/      bOtTOm/      (sCREEn HOlES)
BAsE  FIRSt 40     sECOND 40    tHIRD 40     UNUSeD 8
adDR  #  RANge     #  RANGE     #  RangE     rANGe
$400  00 $400-427  08 $428-44F  16 $450-477  $478-47F
$480  01 $480-4A7  09 $4A8-4CF  17 $4D0-4F7  $4F8-4FF
$500  02 $500-527  10 $528-54F  18 $550-577  $578-57F
$580  03 $580-5A7  11 $5A8-5Cf  19 $5d0-5F7  $5f8-5fF
$600  04 $600-627  12 $628-64F  20 $650-677  $678-67F
$680  05 $680-6A7  13 $6A8-6CF  21 $6D0-6F7  $6F8-6FF
$700  06 $700-727  14 $728-74F  22 $750-777  $778-77f
$780  07 $780-7A7  15 $7A8-7CF  23 $7D0-7f7  $7F8-7ff

Text/LOrES Page 2 followS tHe samE Pattern - JUsT ADD $400 to THe addresses. In Fact HIRES paGEs 1 aNd 2 also FoLloW ExactlY the sAmE PatTern, but repeAted 8 Times each From $2000 anD $4000.
in summaRY, screen Holes aRe sEctIons OF vIdEo mEmORy tHAt Are NOt dIsplayed. teChNicalLy thEY EXIst iN alL vidEo modEs and in both MaIn aNd AuXIllIary mEmory, But tHe Term "sCreen hOles" uSuAlly refers to thoSe in main TEXT pAge 1, WhIch HaVe speCIal sigNifIcaNce as diScussed NExt.
2. whAT ARe Screen holes used
 on a different third of t he screen.  Figu re5.4  f romSath er's Understan d ingthe Apple //e:

Sather 's bo ok s  hav e  a n exc ellentd is c u ssi on  o n t he ho w the  by tes inmemory map  to  t he display f o reach video  mo de. Here are  th e addr es s r a ngesfor  TEXT /LORES page 1  memory f ro m  Figur e  5.5.
  TOP /         MIDDLE/    BOTTOM/     (SCRE EN HO L E S)BAS E  FIRST 4 0    S E COND 40  T H IRD 40     UNUSED  8
ADDR  #RAN GE    #   R A NGE    # RA N GE    RANGE
$ 400 00 $400- 427  0 8  $428-4 4 F  16 $ 450-47 7 $47 8-47 F 
$ 48 0 01 $48 0 -4 A709$4A8-4CF  17  $4D0 -4F7 $ 4 F8-4 FF$500   02$500-527  10$52 8-54 F   1 8 $55 0-577   $5 78 -57F$580 03 $5 80 -5A7  11 $5A8-5 CF 19 $5D0-5 F7 $ 5F8 -5 FF
$6 0 0  04$60 0-6 27  12$628-64 F   2 0$ 6 5 0- 677  $678-67F
$680  0 5  $ 680-6A7 13 $6 A 8- 6C F   21 $6D 0- 6F7   $6 F 8 -6FF$700  0 6 $700-7 27  14 $7 28 -74F  2 2$750-7 77   $ 778 -77F$ 780 07 $7 80-7A7 15 $7 A 8-7CF  23 $7D0 - 7F7  $7F8-7FF 
T E X T/ L ORES  pa ge 2 follow s th e  sam e pa t te rn-  just  add$4 0 0t o the addresses. In  f act HI RES p ages 1 and 2also follo w e xactly t he s a me pattern, but r epeat ed 8 times each fro m $20 00 and $ 4000.
Ins u mmary, s cre enhol esa r esections of v i d eo m em ory tha t a re notdis pla yed . T ec hnicallythey exi st  i nal l v ideom odes and  i n b ot h M ain a n d Auxi lliar y me mo ry ,  bu t the t e rm " scre en  h oles " u su allyrefe r s t o those  in MainTEX T  pag e1,  whichhave specialsi gnificance  a s d iscuss e d  next.
2 . What are screen holes used
 on_a different_third of the screen._Figure 5.4_from_Sather's Understanding_the_Apple //e:

Sather's books_have an excellent_discussion on the how_the bytes in_memory_map to the display for each video mode. Here are the address ranges for_TEXT/LORES_page 1_memory_from_Figure 5.5.
   _  TOP/  _ _    MIDDLE/   __ BOTTOM/ _    (SCREEN HOLES)
BASE  FIRST 40_    SECOND 40_  _THIRD_40_   _UNUSED 8
ADDR  #  RANGE_    # _RANGE     # _RANGE     RANGE
$400_ 00 $400-427  08_$428-44F _16 $450-477  $478-47F
$480 _01 $480-4A7 _09 $4A8-4CF_ 17 $4D0-4F7_ $4F8-4FF
$500  02 $500-527 _10 $528-54F _18 $550-577  $578-57F
$580  03_$580-5A7_ 11 $5A8-5CF__19_$5D0-5F7 _$5F8-5FF
$600  04_$600-627_ 12_$628-64F_ 20 $650-677  $678-67F
$680 _05_$680-6A7  13 $6A8-6CF  21 $6D0-6F7_ $6F8-6FF
$700  06_$700-727_ 14 $728-74F _22 $750-777  $778-77F
$780 _07 $780-7A7  15 $7A8-7CF _23 $7D0-7F7_ $7F8-7FF

TEXT/LORES_page 2 follows the same pattern - just add $400 to_the addresses. In fact HIRES pages_1 and 2 also_follow exactly_the_same pattern, but_repeated_8 times_each from $2000 and $4000.
In summary, screen_holes are_sections of video memory that are_not displayed. Technically they_exist_in all video modes and in_both Main and Auxilliary memory, but_the term "screen holes" usually_refers_to_those in Main TEXT page_1, which have special significance as_discussed next.
2. What_are screen holes used