Add comments to "dmabs.s"
This commit is contained in:
Phil Budne
+121
-107
@@ -1,49 +1,63 @@
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" dmabs
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" dmabs
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" takes a list of files on command line and punches out each
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" to paper tape with a "hardware read-in" (HRI) bootstrap
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" program in front of them.
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" Bob Supnik says:
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" The PDP-7/9/15 hardware read-in used a simple format where
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" the start address was specified in the address switches, and
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" then 18b words were deposited sequentially in memory. Binary
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" format was distinguished by having the high order bit (0200)
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" in each 8b tape frame set, so that leader (all 0s) could be
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" ignored. A frame with bit 1 set (0100) indicated end of
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" load; the last word was supposed to be either a JMP (to
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" start the program running) or a HLT.
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lac o17
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lac o17
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sys creat; punout
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sys creat; punout " open paper tape punch
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spa
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spa
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sys save
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sys save " open failed: dump core
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dac fo
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dac fo
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lac 017777
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lac 017777
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tad d1
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tad d1
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dac name
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dac name " get pointer to argv[0]
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jms space
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jms space " punch 10 inch leader
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100
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100
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loop:
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loop: " loop for input files
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dzm oldsum
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dzm oldsum " clear checksum
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lac initcmd
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lac initcmd
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dac comand
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dac comand " reset command to "dac"
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lac i 017777
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lac i 017777 " get arg count
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sad d4
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sad d4 " anything left?
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jmp stop
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jmp stop " no: stop
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tad dm4
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tad dm4 " decrement argc by 4
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dac i 017777
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dac i 017777
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lac name
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lac name " advance arg pointer
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tad d4
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tad d4
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dac name
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dac name
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dump1:
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dump1: " (label not used)
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lac comand
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lac comand " get command word
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xor dactra
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xor dactra " transmute dac to jmp
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dac tracmd
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dac tracmd
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dump2:
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dump2: " (label not used)
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sys open; name: 0; 0
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sys open; name: 0; 0 " open file
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spa
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spa
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jmp opnerr
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jmp opnerr " open failed
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dac fi
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dac fi " save input fd
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-bootsiz
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-bootsiz " get length of bootstrap
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dac c1
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dac c1
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law boot-1
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law boot-1 " get pointer to boostrap in i8
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dac 8
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dac 8
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1:
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1:
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lac i 8
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lac i 8 " fetch word from bootstrap
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jms put
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jms put " write to tape
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isz c1
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isz c1 " done?
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jmp 1b
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jmp 1b " no: loop
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lac bootcmd
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lac bootcmd " write "jmp" instruction to tape
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lrs 12
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lrs 12
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jms put1
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jms put1
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lac bootcmd
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lac bootcmd
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@@ -51,108 +65,108 @@ dump2:
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jms put1
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jms put1
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lac bootcmd
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lac bootcmd
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and o77
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and o77
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xor o300
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xor o300 " final frame of jmp word: 0100 set
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jms put2
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jms put2
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jms space
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jms space " punch three empty frames
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3
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3
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dump3:
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dump3: " block loop
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-1
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-1 " reset i8 to buffer
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tad bufp
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tad bufp
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dac 8
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dac 8
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-64
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-64 " get count
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dac c1
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dac c1
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1:
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1:
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dzm i 8
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dzm i 8 " loop zeroing buffer
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isz c1
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isz c1
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jmp 1b
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jmp 1b
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lac fi
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lac fi
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sys read; bufp: buf; 64
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sys read; bufp: buf; 64 " read block from input file
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sna
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sna " got some?
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jmp done
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jmp done " done
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dac count
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dac count " save count
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-1
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-1
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tad bufp
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tad bufp
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dac 8
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dac 8 " point i8 to input buffer
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-64
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-64
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dac c1
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dac c1 " reset count
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cla
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cla
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1:
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1: " loop for 1's complement sum of buffer
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add i 8
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add i 8
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isz c1
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isz c1
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jmp 1b
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jmp 1b
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sna
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sna " sum non-zero?
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jmp dump4
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jmp dump4 " no: is zero: skip this block
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dac newsum
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dac newsum " save as new sum
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lac comand
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lac comand " get command word
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jms put
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jms put " write to tape
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lac count
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lac count " get positive count
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jms put
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jms put " write to tape
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lac oldsum
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lac oldsum
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add comand
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add comand
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add count
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add count
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jms put
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jms put " write oldsum+command+count
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lac newsum
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lac newsum " copy new sum to old sum
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dac oldsum
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dac oldsum
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jms space
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jms space " write three empty frame
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3
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3
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-1
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-1 " reset i8 to input buffer
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tad bufp
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tad bufp
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dac 8
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dac 8
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-1
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-1
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tad count
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tad count
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cma
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cma
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dac c1
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dac c1 " reset counter
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1:
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1: " loop writing block to tape
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lac i 8
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lac i 8
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jms put
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jms put
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isz c1
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isz c1
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jmp 1b
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jmp 1b
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jms space
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jms space " follow with 1 inch trailer
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10
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10
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dump4:
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dump4: " end of block
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lac comand
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lac comand " advance command word by count
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tad count
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tad count
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dac comand
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dac comand
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jmp dump3
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jmp dump3 " loop for another block
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done:
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done: " here at end of input file
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lac tracmd
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lac tracmd " get transfer command (jmp)
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jms put " write to tape
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cla " write a zero word
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jms put
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jms put
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cla
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lac oldsum " get checksum
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jms put
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add tracmd " add in jmp command word
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lac oldsum
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jms put " write to tape
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add tracmd
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jms space " write two inch trailer
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jms put
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jms space
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20
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20
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lac fi
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lac fi " close input file
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sys close
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sys close
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jmp loop
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jmp loop " loop for another input file
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stop:
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stop:
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cla
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cla
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jms put
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jms put " write a zero binary word to tape
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jms space
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jms space " write 10 inch trailer
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100
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100
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sys exit
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sys exit
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space: 0
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space: 0 " punch empty frames (count after jms)
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-1
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-1
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tad i space
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tad i space
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cma
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cma
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dac c1
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dac c1 " store negative count
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isz space
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isz space " skip count word
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1:
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1:
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lac o400
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lac o400 " defeat NUL removal
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jms put2
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jms put2 " write one empty frame
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isz c1
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isz c1 " done?
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jmp 1b
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jmp 1b " no
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jmp i space
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jmp i space
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put: 0
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put: 0 " write a (binary) word (as three frames)
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dac 1f
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dac 1f
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lrs 12
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lrs 12
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jms put1
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jms put1
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@@ -164,13 +178,13 @@ put: 0
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jmp i put
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jmp i put
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1:0
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1:0
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put1:0
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put1:0 " write one frame of a binary word
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and o77
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and o77
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xor o200
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xor o200 " light the high bit
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jms put2
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jms put2
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jmp i put1
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jmp i put1
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put2: 0
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put2: 0 " write one frame to tape
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dac 1f
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dac 1f
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lac fo
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lac fo
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sys write; 1f; 1
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sys write; 1f; 1
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@@ -180,37 +194,37 @@ put2: 0
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boot:
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boot:
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org = 017740
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org = 017740
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2:
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2:
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jms get1-boot+org
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jms get1-boot+org " get command word from tape
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dac cmd-boot+org
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dac cmd-boot+org
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jms get1-boot+org
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jms get1-boot+org " get count from tape
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cma
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cma
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dac cnt-boot+org
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dac cnt-boot+org " store complemented (incremented below)
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jms get2-boot+org
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jms get2-boot+org " get checksum word
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xor sum-boot+org
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xor sum-boot+org " clear those bits in sum
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dzm sum-boot+org
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dzm sum-boot+org " clear out sum
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cla cll sza
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cla cll sza " checksum match? & clear AC & LINK
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hlt
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hlt " no: checksum mismatch
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isz cnt-boot+org
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isz cnt-boot+org " yes: increment count (complete negate)
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1:
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1:
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jms get1-boot+org
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jms get1-boot+org " get data word from tape
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cmd: 0
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cmd: 0 " command word (read from tape)
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isz cmd-boot+org
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isz cmd-boot+org " increment command instruction
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isz cnt-boot+org
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isz cnt-boot+org " increment count
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jmp 1b-boot+org
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jmp 1b-boot+org " not done, keep going
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jmp 2b-boot+org
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jmp 2b-boot+org
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get1: 0
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get1: 0 " get checksummed word from tape
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jms get2-boot+org
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jms get2-boot+org " read a word
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dac get2-boot+org
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dac get2-boot+org " save (in get2 return addr word!)
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add sum-boot+org
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add sum-boot+org " 1's complement sum
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dac sum-boot+org
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dac sum-boot+org " save sum
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lac get2-boot+org
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lac get2-boot+org " get word back
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jmp i get1-boot+org
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jmp i get1-boot+org " return
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get2: 0
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get2: 0 " get unchecksummed word from tape
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iot 0144
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iot 0144 " "rsb" ptr select binary mode
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1:
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1:
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iot 0101
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iot 0101 " "rsf" ptr skip if flag set
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jmp 1b-boot+org
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jmp 1b-boot+org " loop until ready
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iot 0112
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iot 0112 " "rrb" ptr clear flag, or in read buffer
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jmp i get2-boot+org
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jmp i get2-boot+org
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sum: 0
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sum: 0
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cnt = sum+1
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cnt = sum+1
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@@ -226,12 +240,12 @@ opnerr:
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sys write; mes; 2
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sys write; mes; 2
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jmp loop
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jmp loop
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mes:
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mes:
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040;077012
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040;077012 " space, ?, NL
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comand: 0
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comand: 0
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tracmd: 0
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tracmd: 0
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d1: 1
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d1: 1
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.17777: 017777
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o17777: 017777 " unused?
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o77: 077
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o77: 077
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o200: 0200
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o200: 0200
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o300: 0300
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o300: 0300
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