AmstradCPC6128-hypertext-en-Sinewalker

250 y=0:b=150:GOSUB 400
260 x=575:a=-240:y=400:b=-150:GOSUB 400
270 y=0:b=150:GOSUB 400
280 gp=2:GRAPHICS PEN gp:w=40
290 a=240:x=-40:y=400:b=-150:GOSUB 400
300 x=0:y=0:b=150:GOSUB 400
310 a=-240:x=640:y=0:b=150:GOSUB 400
320 x=600:y=400:b=-150:GOSUB 400
330 ORIGIN 0,0,256,380,0,400:CLG 1
340 ORIGIN 0,0,0,640,150,250:CLG 1
350 ORIGIN 0,0,280,352,0,400:CLG 2
360 ORIGIN 0,0,0,640,168,230:CLG 2
370 SAVE dumpfi Le$,b,&C000,&4000
380 DATA 2,26,6
390 END
400 MOVE x,y:DRAWR a,b:DRAWR w,0:DRAWR -a,-b
410 MOVE x+a/2+w/2,y+b/2:FILL gp
420 RETURN
430 errnum=ERR:RESUME NEXT
run
Note the use of • D A T and. SRN filetypes. These filetypes are used to remind us of
what is in the file, rather than because they have any inherent significance. The file
PAR A M • D A T will be an ASCII data file without a header, whilst F LA G DUM P • SRN
is an AMSDOS binary file with a header.
Note how the program deliberately tries to read from the file PAR A M • D A T before
writing to it, in order to establish if the file already exists. If the file does NOT exist,
then an error is reported by BASIC; the error is trapped by the program, and
execution proceeds without interruption. If the file DOES already exist, then no error
is reported, and the program automatically asks if you wish to overwrite the existing
file.
The particulars of the screen dump, namely the screen mode, palette colours and
name of file containing the actual information, are saved into a parameter file. This
illustrates the use of a data file to W RI T E program variables (d u m p f i L e $) and
constants ( 1 ), saving them for use by another program.
AMSDOS and CPIM Chapter 5 Page 7