more documentation of similarities and avoiding them where practicable.

strings/18692885

@@ -0,0 +1,5 @@
+CLC / ADC #40 / STA $nn
+
+Add 40 to a ZP location.  No creativity here. 
+Effectivelhy only one insstruction.
+Not copyrightable.

strings/424153494320

@@ -0,0 +1,4 @@
+string "BASIC "
+
+Since we are writing a BASIC language interprettor, such a string is expected.
+BASIC appears in many other works. It cannot be copyrighted as a word.

strings/4241534943205632

@@ -0,0 +1,8 @@
+String "BASIC V2"
+
+As we are implementing a V2 class BASIC interprettor, it is 
+natural for us to include this string.
+There are many BASIC intreprettors, and the word cannot be
+copyrighted, nor it is reasonable to contemplate that a party
+could be constrained from having a BASIC with version 2, or
+displaying that information anywhere. Not copyrightable.

strings/60AD8D02

@@ -0,0 +1,7 @@
+RTS + LDA $028D
+
+RTS is a very common instruction, as is loading A from absolute address.
+The RTS is the end of a routine, and the LDA $028D thus the start of
+another. Thus this would occur whenever a routine begins with loading
+A from $028D, immediately after another routine.  Nothing creative.
+Not copyrightable.

strings/7702E8

@@ -0,0 +1,3 @@
+Something with $0277 / INX
+
+Only one whole instruction here. Not copyrightable.

strings/860291F3

@@ -0,0 +1,3 @@
+something with $0286 / STA ($F3),Y
+
+Only one whole instruction. Not copyrightable.

strings/88B1D1C891D188

@@ -0,0 +1,44 @@
+Copy screen + colour RAM to the right one place
+
+This sequence of instructions:
+
+loop:
+       DEY
+       LDA ($D1),Y
+       INY
+       STA ($D1),Y
+       DEY
+       LDA ($F3),Y
+       INY
+       STA ($F3),Y
+       DEY
+       CPY $D3
+       BNE loop
+       LDA #$20
+       STA ($D1),Y
+
+is the obvious any minimal way to copy the screen and colour RAM data.
+The constants $D1 and $F3 are fixed by the publicly documented interface
+of the KERNAL to point to the screen and colour RAM of the screen.
+
+The Y register is the only register that can be used to post-increment an
+indirect address on the 6502.
+
+Thus the only efficient manner to copy a string to the right one byte
+is to read, increment Y by one to get the destination address, store,
+then decrement Y again so that it points to the source offset, now read
+the colour RAM byte, add one to Y so that we point to the destination,
+and then write it.  
+
+Similarly the check against $D3 (current column of cursor on screen) is also
+necessary for working out when to terminate the loop.  The storing of $20
+into the screen RAM is also required to effect the insertion of a space.
+
+In fact, about the only variant possible would be to swap the $D1 and $F3
+constants so that the colour RAM is copied before the screen RAM in each
+loop, instead of after it.
+
+It is telling that this routine was the result of independent implementation
+of this routine, without looking at the KERNALs routine, in terms of supporting
+the argument that the routine is the obvious manner in which to do this.
+

strings/88B1F3C891F388

@@ -0,0 +1,44 @@
+Copy screen + colour RAM to the right one place
+
+This sequence of instructions:
+
+loop:
+       DEY
+       LDA ($D1),Y
+       INY
+       STA ($D1),Y
+       DEY
+       LDA ($F3),Y
+       INY
+       STA ($F3),Y
+       DEY
+       CPY $D3
+       BNE loop
+       LDA #$20
+       STA ($D1),Y
+
+is the obvious any minimal way to copy the screen and colour RAM data.
+The constants $D1 and $F3 are fixed by the publicly documented interface
+of the KERNAL to point to the screen and colour RAM of the screen.
+
+The Y register is the only register that can be used to post-increment an
+indirect address on the 6502.
+
+Thus the only efficient manner to copy a string to the right one byte
+is to read, increment Y by one to get the destination address, store,
+then decrement Y again so that it points to the source offset, now read
+the colour RAM byte, add one to Y so that we point to the destination,
+and then write it.  
+
+Similarly the check against $D3 (current column of cursor on screen) is also
+necessary for working out when to terminate the loop.  The storing of $20
+into the screen RAM is also required to effect the insertion of a space.
+
+In fact, about the only variant possible would be to swap the $D1 and $F3
+constants so that the colour RAM is copied before the screen RAM in each
+loop, instead of after it.
+
+It is telling that this routine was the result of independent implementation
+of this routine, without looking at the KERNALs routine, in terms of supporting
+the argument that the routine is the obvious manner in which to do this.
+

strings/8D02C903D0

@@ -0,0 +1,4 @@
+something with $028D / CMP #$03 / BNE somewhere
+
+Only one whole instruction. Nothing creative.
+Not copyrightable.

strings/8D8C02A90E8D8602A9

@@ -0,0 +1 @@
+STA $028C / LDA #$0E / STA $0286 / LDA 

strings/A6C6EC8902

@@ -0,0 +1,3 @@
+Use X register to compare contents of a ZP and absolute address location
+
+Nothing copyrightable here in this simple comparison of memory contents.

strings/B1D1C920

@@ -0,0 +1,4 @@
+LDA ($D1),Y / CMP #$20
+
+Compare a byte read from a pointer with a specific value.
+No creativity here. Not copyrightable.

strings/E6C911D0

@@ -0,0 +1,3 @@
+Fragment / CMP #$11 / BNE somewhere
+
+Only one whole intruction here. Not copyrightable.

strings/E6C913D0

@@ -0,0 +1,3 @@
+Fragment / CMP #$13 / BNE somewhere
+
+Only one whole intruction here. Not copyrightable.