Epson PX-8 User Manual page 54

a) The "SAVE 9 GO.COM" Trick
There is a special trick you can play on the PX-8 using the SAVE command
which can be very helpful in various circumstances. When you exit a program
it is still present in memory. For example when exiting BASIC using the 'sys-
tem' command, the BASIC interpreter and the programs in the five program
areas are still existant in memory as far as MENU is on. You may then remem-
ber that one of the programs should have been saved, and will be lost if you
try
t~
restart BASIC.
Als~
you
~ight
load a program such as PIP, then having
used It once to transfer a smgle fIle done nothing except a DIR or ERA or other
minor operation, and then wish to use it again. In either case the program (the
BASIC interpreter, PIP or whatever) can be recalled instantly if you know how
instead of having to be reloaded from disk or even tape. In the case of BASIC
the five programs stored in memory can be recovered just as if you had not
exited to CP/M. First you have to create a file called GO.COM then execute
it when you wish to continue with the previous program by typing GO. To cre-
ate this file all you have to do is type:
A> SAVE 9 GO.COM
or
A>SAVE 9 D:GO.COM
If
you want it on the D: drive, for instance. what you are actually doing with
this command is making a file of length 0 bytes and saving it on the specified
drive. When you type GO at the prompt the program GO.COM (of length 0
bytes) is loaded into memory and executed. Because the file contains 0 bytes
it does not overwrite the program already in memory, so in fact the program
already there is executed instead.
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3.7.5
TYPE
(Displaying the contents of a file)
".UIIF"
TYPE filename
This command is used to display a file on the screen. There must be a space
between TYPE and the filename. This is usually an ASCII file because any other
data format results in a screenful of rubbish and is totally incomprehensible.
This is because as the computer reads through the file it tries to convert all the
hexadecimal numbers it finds into printable ASCII characters, and the only files
which produce anything recognisable are those which are in ASCII format. For
example,if you wanted to look at a BASIC program file using TYPE, it would
have to have been SAVEd in ASCII format using the" ,A" option in BASIC.
Normally, BASIC programs are stored in compressed binary format which will
produce some very strange results if it is TYPEd to the screen.
a) Displaying the contents of a file'to the screen
The command is invoked either to show the contents of a file from the current
drive:
A> TYPE TEXT .TXT
or for example:
C>TYPE D:DATAFILE.DOC
will display the contents ofthe file DATAFILE.DOC which is held on drive D:.
The only files which you can be sure will contain data in ASCII format are
those with the extensions ASM, PRN and DOC or TXT. Others may be in this
format, and it doesn't do any harm to look at them anyway if you want to
in order to check. WILDCARDS cannot be used with the TYPE command.
If
the file is not on the disk the filename will be repeated on the next line with
a question mark after it, for example:
C>TYPE B:TEXTl.DOC
B:TEXTl.DOC?
This would also happen if an attempt was made to use wildcard characters.
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