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/ vim: set sw=8 noexpandtab :
*000
INTRET, 0
JMP GOTINT
INPUTY, 1000 / Address of youngest byte in input buffer
INPUTO, 1000 / Address of oldest byte in input buffer
*200
/ Main program enables keyboard interrupt, then enters echo loop
KIE
ION
LOOP, TSF / Call ECHO if printer is ready
JMS ECHO
JMP LOOP
ECHO, 0
TAD INPUTO
CMA IAC / Negate
TAD INPUTY
SNA / Abandon echo if input buffer is empty (n.b. or full, because we don't have wrap bits)
JMP I ECHO
TAD I INPUTO / Read from input buffer
TLS / Print
JMS FIXO
JMP I ECHO
GOTINT, KSF / Skip reading keyboard if nothing was typed
JMP NOIN
DCA SAVED
KRB / Read from keyboard
DCA I INPUTY / Write to input buffer
JMS FIXY
CLA
TAD SAVED
NOIN, RMF
ION
JMP I INTRET
/ Wrap INPUTY pointer at 2000 back to 1000
FIXY, 0
TAD INPUTY
TAD [-2000]
SZA
JMP I FIXY
CLA
TAD [1000]
DCA INPUTY
JMP I FIXY
/ Wrap INPUTO pointer at 2000 back to 1000
FIXO, 0
TAD INPUTO
TAD [-2000]
SZA
JMP I FIXO
CLA
TAD [1000]
DCA INPUTO
JMP I FIXO
*300
SAVED, 0
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