1000 STATP%=241:DATP%=240:' status and data ports for the graphics card
1010 GOSUB 1190:PRINT"                    <<<  LOAD or DUMP GRAPHICS SCREEN  >>>":PRINT:PRINT:PRINT
1020 PRINT"Purpose:":PRINT:PRINT"     To save the screen graphics into a data file or to restore the screen"
1030 PRINT"     graphics from data file":PRINT:PRINT:PRINT"Method:":PRINT
1040 PRINT"     Each pixel on the graphics screen represent one bit of data.  On the"
1050 PRINT"     512x490 pixel screen that is 31,360 bytes of data.  The reading of the"
1060 PRINT"     graphics screen is done byte-wise by issuing command to read from the"
1070 PRINT"     screen memory.":FOR I%=1 TO 6:PRINT:NEXT:INPUT"Press ENTER to continue. ",A$
1080 M%=22:N%=1:GOSUB 1200:INPUT"Load or dump the graphics screen? (L/D) ",A$:IF A$<>"L" AND A$<>"D" THEN 1080
1090 IF A$="L" THEN LD%=1 ELSE LD%=0:' set the flag, load=1 dump=0
1100 GOSUB 1190:FOR I%=1 TO 10:PRINT:NEXT:PRINT"     Type the filename in UPPER case.  No check on file existence or"
1110 PRINT"     legality is provided.  Drive letter and colon can be included."
1120 GOSUB 1200:LINE INPUT"Filename: ",A$:IF A$="" THEN 1130 ELSE 1150
1130 GOSUB 1200:INPUT"Exit this program? (Y/N) ",A$:IF A$<>"Y" AND A$<>"N" THEN 1130
1140 IF A$="N" THEN 1000 ELSE END
1150 F$=A$:FL%=1:GOSUB 1240:IF LD%=1 THEN 1160 ELSE 1170
1160 BT%=165:GOSUB 1270:FOR I%=1 TO 30912:GET#1,I%:BT%=ASC(R$):GOSUB 1270:NEXT:CLOSE:GOSUB 1310:GOTO 1130
1170 BT%=164:GOSUB 1270:FOR I%=1 TO 30912:GOSUB 1280:LSET R$=CHR$(BT%):PUT#1,I%:NEXT:CLOSE:GOSUB 1310:GOTO 1130
1180 ' Codes are for the Televideo terminal
1190 PRINT CHR$(27)CHR$(42):RETURN:' clear the whole screen
1200 GOSUB 1220:PRINT CHR$(27)CHR$(89):GOSUB 1220:RETURN:' clear to the end of screen from the current cursot position
1210 GOSUB 1220:PRINT CHR$(27)CHR$(84):GOSUB 1220:RETURN:' clear to the end of line from the current cursot position
1220 PRINT CHR$(27)CHR$(61)CHR$(M%+31)CHR$(N%+31);:RETURN:' direct cursor address (set the cursor position)
1230 ' Subroutine to open a data file for random access, F$=filename, FL%=rec length
1240 OPEN"R",#1,F$,FL%:FIELD#1,FL% AS R$:RETURN
1250 ' Subroutines to send data to the GDC-512 board
1260 BT%=INT(WD%/256):GOSUB 1270:BT%=(WD% AND 255):GOSUB 1270:RETURN:' Subroutine to output a 16-bit data
1270 IF (INP(STATP%) AND 1)>0 THEN 1270 ELSE OUT(DATP%),(BT% AND 255):RETURN:' Subroutine to output a 8-bit data
1280 IF (INP(STATP%) AND 2)=0 THEN 1280 ELSE BT%=INP(DATP%):RETURN:' Subroutine to read a 8-bit data
1290 GOSUB 1280:WD%=BT%*256:GOSUB 1280:WD%=WD%+BT%:RETURN:' Subroutine to read a 16-bit data
1300 ' Subroutine to reset the GDC512 but not to clear the graphics
1310 OUT(STATP%),1:OUT(STATP%),0:RETURN
1320 END