Implements suggested changes.

src/main/resources/assets/computercraft/lua/rom/apis/paintutils.lua

@@ -12,8 +12,8 @@ end
 
 local tColourLookup = {}
 for n=1,16 do
-    tColourLookup[ string.sub( "0123456789abcdef",n,n ) ] = 2^(n-1)
-    tColourLookup[ 2^(n-1) ] = string.sub( "0123456789abcdef",n,n )
+    tColourLookup[ string.byte( "0123456789abcdef",n,n ) ] = 2^(n-1)
+    tColourLookup[ 2^(n-1) ] = string.byte( "0123456789abcdef",n,n )
 end
 
 function loadImage( sPath )
@@ -26,7 +26,7 @@ function loadImage( sPath )
         for sLine in io.lines(sPath) do
             local tLine = {}
             for x=1,#sLine do
-                tLine[x] = tColourLookup[ string.sub(sLine,x,x) ] or 0
+                tLine[x] = tColourLookup[ string.byte(sLine,x,x) ] or 0
             end
             table.insert( tImage, tLine )
         end

src/main/resources/assets/computercraft/lua/rom/help/edit.txt

@@ -1,4 +1,6 @@
 edit is a text editor for creating or modifying programs or text files. After creating a program with edit, type its filename in the shell to run it. You can open any of the builtin programs with edit to learn how to program.
 
 ex:
-"edit hello" opens a file called "hello" for editing.
+"edit hello" opens a file called "hello" for editing.
+
+By changing setting "edit.advanced_functionality" to true you can unlock ability to jump to specific line in longer files.

src/main/resources/assets/computercraft/lua/rom/programs/edit.lua

@@ -59,7 +59,9 @@ end
 if peripheral.find( "printer" ) then
     table.insert( tMenuItems, "Print" )
 end
-table.insert( tMenuItems, "Jump" )
+if settings.get( "edit.advanced_functionality" ) then
+    table.insert( tMenuItems, "Jump" )
+end
 table.insert( tMenuItems, "Exit" )
 
 local sStatus = "Press Ctrl to access menu"