Here is some old code for you...

The Apple ][ computer didn't have super fancy graphics.  They had a portion of memory mapped to the graphic screen.  Since I don't really feel like trying to explain it here because others have done it far better than I could read this: http://en.wikipedia.org/wiki/Apple_II_graphics   Specifically the Hires Graphics section.

Now, I had a need to be able to scroll the Hires Screen left or right.  Thanks to a series of articles by David Lubar in Creative Computing called The Graph Paper (October 1982 -> March 1983) and an article called Lookup Tables (March 1982) I had a very good understanding of how each byte in memory made up the picture that was displayed so I wrote the following code using the SC Macro Assembler.  This version of the code did the scroll left.

The 'Lookup Table' allowed me to access each line of the hires screen directly and in order (since the screen was 'interlaced').

BTW, comments are for losers. :)

1000        .OR $6000

1010        .TF SCROLLLEFT

1020        .LIST OFF

1030        JMP HERE

1040 TABLHI .HS 2024282C3034383C

1050        .HS 2024282C3034383C

1060        .HS 2125292D3135393D 

1070        .HS 2125292D3135393D

1080        .HS 22262A2E32363A3E

1090        .HS 22262A2E32363A3E

1100        .HS 23272B2F33373B3F

1110        .HS 23272B2F33373B3F

1120        .HS 2024282C3034383C 

1130        .HS 2024282C3034383C

1140        .HS 2125292D3135393D 

1150        .HS 2125292D3135393D

1160        .HS 22262A2E32363A3E

1170        .HS 22262A2E32363A3E 

1180        .HS 23272B2F33373B3F

1190        .HS 23272B2F33373B3F

1200        .HS 2024282C3034383C 

1210        .HS 2024282C3034383C

1220        .HS 2125292D3135393D

1230        .HS 2125292D3135393D

1240        .HS 22262A2E32363A3E 

1250        .HS 22262A2E32363A3E

1260        .HS 23272B2F33373B3F

1270        .HS 23272B2F33373B3F

1280 TABLLO .HS 0000000000000000

1290        .HS 8080808080808080

1300        .HS 0000000000000000

1310        .HS 8080808080808080

1320        .HS 0000000000000000 

1330        .HS 8080808080808080 

1340        .HS 0000000000000000

1350        .HS 8080808080808080

1360        .HS 2828282828282828

1370        .HS A8A8A8A8A8A8A8A8

1380        .HS 2828282828282828

1390        .HS A8A8A8A8A8A8A8A8 

1400        .HS 2828282828282828 

1410        .HS A8A8A8A8A8A8A8A8 

1420        .HS 2828282828282828 

1430        .HS A8A8A8A8A8A8A8A8 

1440        .HS 5050505050505050

1450        .HS D0D0D0D0D0D0D0D0

1460        .HS 5050505050505050 

1470        .HS D0D0D0D0D0D0D0D0 

1480        .HS 5050505050505050 

1490        .HS D0D0D0D0D0D0D0D0

1500        .HS 5050505050505050 

1510        .HS D0D0D0D0D0D0D0D0 

1520 HERE   STA $C050 

1530        STA $C057

1540        STA $C054

1550        STA $C052

1560        LDX #$00

1570 A7     LDA TABLLO,X  

1580        STA $F0

1590        LDA TABLHI,X

1600        STA $F1

1610        CLC

1620        LDY #$27

1630 A6     LDA ($F0),Y

1640        ROL

1650        BCC A1

1660        ROR

1670        BCC A2

1680        SEC

1690        ROR

1710        JMP A3

1720 A2     ROL

1730        CLC

1740        ROR

1750        SEC

1760        ROR

1770        JMPA3

1780 A1     ROR

1790        BCC A4

1800        ROL

1810        SEC

1820        ROR

1830 A4     ROR

1840 A3     STA ($F0),Y

1850        ROR

1860        DEY

1870        BMI A5

1880        ROL

1890        JMP A6

1900 A5     INX

1910        CPX #$C0

1920        BNE A7

1930        RTS

And the code to scroll right looks like this:

1000        .OR $6000

1010        .TF SCROLLRGHT

1020        .LIST OFF

1030        JMP HERE

1040 TABLHI .HS 2024282C3034383C

1050        .HS 2024282C3034383C

1060        .HS 2125292D3135393D 

1070        .HS 2125292D3135393D

1080        .HS 22262A2E32363A3E

1090        .HS 22262A2E32363A3E

1100        .HS 23272B2F33373B3F

1110        .HS 23272B2F33373B3F

1120        .HS 2024282C3034383C 

1130        .HS 2024282C3034383C

1140        .HS 2125292D3135393D 

1150        .HS 2125292D3135393D

1160        .HS 22262A2E32363A3E

1170        .HS 22262A2E32363A3E 

1180        .HS 23272B2F33373B3F

1190        .HS 23272B2F33373B3F

1200        .HS 2024282C3034383C 

1210        .HS 2024282C3034383C

1220        .HS 2125292D3135393D

1230        .HS 2125292D3135393D

1240        .HS 22262A2E32363A3E 

1250        .HS 22262A2E32363A3E

1260        .HS 23272B2F33373B3F

1270        .HS 23272B2F33373B3F

1280 TABLLO .HS 0000000000000000

1290        .HS 8080808080808080

1300        .HS 0000000000000000

1310        .HS 8080808080808080

1320        .HS 0000000000000000 

1330        .HS 8080808080808080 

1340        .HS 0000000000000000

1350        .HS 8080808080808080

1360        .HS 2828282828282828

1370        .HS A8A8A8A8A8A8A8A8

1380        .HS 2828282828282828

1390        .HS A8A8A8A8A8A8A8A8 

1400        .HS 2828282828282828 

1410        .HS A8A8A8A8A8A8A8A8 

1420        .HS 2828282828282828 

1430        .HS A8A8A8A8A8A8A8A8 

1440        .HS 5050505050505050

1450        .HS D0D0D0D0D0D0D0D0

1460        .HS 5050505050505050 

1470        .HS D0D0D0D0D0D0D0D0 

1480        .HS 5050505050505050 

1490        .HS D0D0D0D0D0D0D0D0

1500        .HS 5050505050505050 

1510        .HS D0D0D0D0D0D0D0D0 

1520 HERE   STA $C050 

1530        STA $C057

1540        STA $C054

1550        STA $C052

1560        LDX #$00

1570 A7     LDA TABLLO,X  

1580        STA $F0

1590        LDA TABLHI,X

1600        STA $F1

1610        CLC

1620        LDY #$00

1630 A6     LDA ($F0),Y

1640        ROL

1650        BCC A1

1660        ROL

1670        BCC A2

1680        SEC

1690        ROR

1700        SEC

1710        BCS A3

1720 A2     SEC

1730        ROR

1740        CLC

1750        BCC A3

1760 A1     ROL

1770        BCC A4

1780        CLC

1790        ROR

1800        SEC

1810        BCS A3

1820 A4     CLC

1830        ROR

1840        CLC

1850 A3     STA ($F0),Y

1860        ROR

1870        INY

1880        CPY #$28

1890        BEQ A5

1900        ROL

1910        JMP A6

1920 A5     INX

1930        CPX #$C0

1940        BNE A7

1950        RTS

The code is very close but there are some important differences (like line 1620, 00 starts on the left of the line and #27 starts on the right of the line).

Now, you may ask, Why did I bother posting this?  Because I could and I felt like sharing.  I do have some old notebook pages I found with some hand written code on them that I'm going to scan in and post here at some point in the near future.