Part 20
File operations
Subjects covered...
Drives
FORMAT
Filenames
SAVE, LOAD
Disk catalog: CAT
Wildcards
MERGE
Deleting and renaming files
File attributes
ERASE, MOVE, COPY
The RAMdisk
Tape operations
VERIFY
Tape catalog: CAT
Drives
The +3 has a built-in disk drive that can be used to save and load
your own programs, and to load programs produced by other people. As
it is also possible to connect a second disk drive to the +3, BASIC
must have some way of identifying which disk drive is which. The
built-in drive is known as drive A: (always followed by a colon
because +3 BASIC knows that when you say A:, you mean 'disk drive A').
If the external drive is present, it is referred to as drive B:.
As the processor at the heart of the +3 can only converse with 64K of
memory at a time, the extra RAM in the +3's 128K memory is used just
like another drive. This is called the RAMdisk and is identified by
the letter M: (for memory drive). All the commands (except FORMAT)
that you can use on drives A: and B: can also be used on drive M:.
Drive M: is much faster than the mechanical disk drives, but it is
very important to remember that just like the contents of the program
memory, the contents of drive M: are erased if you press the RESET
button or switch off the +3. BASIC's NEW command, however, will leave
any files stored on drive M: intact.
If you don't have a second disk drive connected to your +3, you can
still use the machine as if drive B: were present. If you ask the
machine to perform an operation on drive B: (you'll see how to do this
later), a message will appear asking you to...
Please put the disk for B: into the drive then press any key
...whereupon you should put the disk that you would have used in drive
B: (if it had existed) into drive A: then press any key (for example
ENTER). From then on, the machine will treat the built-in disk drive
as if it really were drive B:. When the +3 next needs to perform some
operation on the disk that was originally in the drive, it will ask
you to...
Please put the disk for A: into the drive then press any key
This technique will be particularly useful when using the COPY command
(described later in this section).
Now that you know which drives are available and what they are called,
let's see what they can be used for. Type in the short program (which
displays coloured squares) that you first met at the end of part 16,
i.e....
10 POKE 22527+ RND *704, RND *127
20 GO TO 10
This is the program that you are going to save to disk.
As previously explained (in chapter 6), you cannot simply unwrap a
brand new disk and hope to save programs onto it straight away; it
must first be made ready to use with the aid of the FORMAT command.
FORMAT will erase anything that was previously on the disk and set it
up for +3 BASIC to use. Be careful, therefore, not to FORMAT any disk
that has programs on it you might like to keep. To format your new
disk, type in the following...
FORMAT "a:"
If you haven't already put your new disk into the drive, don't worry -
the +3 will just come back with the error report 'Drive not ready'.
In this case, put your new disk into drive A: and re-type the command.
By the way, while you are using the various disk commands you may
occasionally see the report 'Drive A: not ready' (possibly followed by
'- Retry, Ignore or Cancel ?'). This invariably means that you have
forgotten to put a disk into the drive.
Whenever a report appears that ends with '- Retry, Ignore or Cancel
?', there are three options open to you.
The first is to take action to rectify the problem, for example, if the
report was 'Drive not ready', then put a disk into the drive and type
'R' (to retry). The disk system will then try to carry out the same
operation again and hopefully this time it will succeed.
If you were half way through copying a large file and an error such as
'Missing address mark' appeared, this would usually mean that the disk
being read has been damaged in some way. Try 'R' a few times and if
the error persists, you indeed have a damaged disk. At this stage,
you'll probably want to salvage any un-damaged data, so try typing 'I'
(to ignore). Although this tells the +3's disk system to ignore the
error, there is no guarantee that all your data will be read intact -
it's really just a last ditch operation when all else has failed.
Finally, if you have tried to perform an operation where an error
occurs, you may realise that there is no point in trying to go on. In
this case type 'C' (to cancel) which tells the +3's disk system to
abandon the current command. Having typed 'C', BASIC will report an
error (usually very similar to the text of the previous report.
Back to out attempt to format a disk. If you have made a mistake and
the disk you put into drive A: has already been formatted, the +3 will
spot this and you will receive the report...
Disk is already formatted, A to abandon, other key continue
This is a safety feature that will allow you to abandon the format
before the process gets going, if, by some chance, you inserted the
wrong disk. In this case, you should type 'A' (to abandon) and nothing
more will happen. If, however, you really do intend to reformat the
disk and don't mind losing what's on it, then press any key apart from
'A' (e.g. press ENTER).
After about 30 seconds, the usual '0 OK' report will appear. The disk
is now usable and should not need to be formatted again. You can
always reformat a disk if you wish to clear the disk of data
completely, but remember that it is an irreversible process.
Disks can occasionally become spoilt (corrupted). This can happen if
some dust or dirt comes into contact with the disk surface, if the
disk is left too close to a magnetic field (such as that produced by a
TV or a telephone), if the disk is ejected while it is being written
to, or if the disk is left in the drive when the computer is switched
on or off. A corrupted disk will cause errors during LOAD or SAVE, and
should be reformatted before any more data is saved onto it.
If you want to recover files from a corrupted disk, you can try to
copy them individually (using COPY) to a known 'good' disk. If one or
more files prove uncopiable, then you have probably lost them for
good. We recommend that you keep at least two copies of important
files (on different disks) - one for day-to-day use, and one kept in a
safe place just in case the unthinkable happens. Making regular copies
of valuable data and programs is known as backing-up, and is an
essential habit to get into. Backing-up can save you untold misery and
tears. You can of course make back-ups onto tape, which may prove
cheaper in the long run.
Unlike many computers, the FORMAT command is built-in and can be used
like any other BASIC command. It doesn't affect the program you have
in the computer, so you can save the little two-line program you typed
in a moment ago.
Type in the following...
SAVE "squares"
The words 'SQUARES' is just a name that you use to 'label' the program
you are going to store on disk. To prevent confusion, everything
stored on disk must be given a name. These names (called filenames)
are a little different from those that you may use when storing
programs on tape.
Filenames
The range of characters that you are allowed to use for disk filenames
is more limited than for tape filenames. The format of filenames used
on +3 disks is the same as that used by an operating system known as
CP/M (Control Program/Monitor) by Digital Research Inc. The fact that
these formats are the same means that you can take a +3 disk and use
it on other computers. Data can be transferred in this way between the
+3 and a CP/M system, and this is most likely to be useful for people
writing machine code programs or moving text from a +3 word processor
to a CP/M program. (It is extremely unlikely that programs written in
BASIC can be usefully converted from one machine to another using this
method.)
Filenames can be as simple as the example above - 'SQUARES' (or even
simpler - 'S', for example). However a full CP/M-type filename can be
made up of as many as four parts: user number, drive letter, name and
type. Each of these parts is called a field (e.g. the name field or
the type field).
You needn't worry about what user number means; if you don't know
already, then it's probably best to remain blissfully ignorant.
However, for anyone who is interested: on CP/M machines with very
large disk capacities (or hard disks) with perhaps more than one
terminal connected, user numbers are used to partition files into
subsections (known as user areas) so that there isn't just one huge
directory with several thousand files. On the +3, however, disks
cannot have more than 64 files, so the use of user areas is not really
necessary. Nevertheless, user areas can be specified in filenames used
in +3 disk commands. They take the form...
user number drive letter : filename
...where user number is in the range 0 to 15, and drive letter is A:,
B: or M:. If you specify a user number, then you must also specify a
drive letter. So, to save our example program in user area 5, we would
use...
SAVE "5a:squares"
The problem with using user areas is that it's quite easy to forget
which user area you saved a file to, and so finding it could take a
while (as the CAT command can only catalog one user area at a time).
As just mentioned, the drive letter will normally be A:, B: or M:.
notice that the letter must be followed by a colon (e.g. 'a:squares').
If you don't specify a drive letter, then +3 BASIC will use the drive
that was last used - this is known as the default drive. (When you
first switch on the +3, the default drive is set to A:.) So typing...
SAVE "squares"
...is just as if you had typed...
SAVE "a:squares"
There are special forms of SAVE and LOAD which can be used to change
the default drive. When SAVE or LOAD is followed by a filename that
contains nothing but a drive letter and a colon, the drive identified
by the letter is then made the new default drive. So...
SAVE "m:"
SAVE "squares"
...will change the default drive to drive M: then save the program
onto drive M:. (If the above command had been 'SAVE "m:squares"' the
program would still have been saved to drive M: though the default
drive would not have been changed.)
To switch the default back to drive A:, type...
SAVE "a:"
Note that SAVE and LOAD followed by just a drive letter (and colon)
wildcard will do nothing other than change the default drive. They
certainly won't save or load a program. You must use SAVE or LOAD
followed by a real filename for this.
The name field of a filename is the only field that you have to
specify when using SAVE, LOAD, etc. The name field can be from 1 to 8
characters long and may contain any of the following:
Letters: abcdefghijklmnopqrstuvwxyz (upper or lower case)
Digits: 0123456789
Other characters: "#$'@^_{}~`
[The backquote (`) should really be a pound sign; pity nobody noticed
that before they printed the manual :-)]
Upper and lower case letters are the same in filenames, so 'EXAMPLE'
and 'example' would be identical.
A filename can end with an optional type field (which is just a
further three characters) that you may wish to use in order to group
together files of the same type. If a type field is specified, it must
be preceded by a dot. (Unlike some other BASICs, +3 BASIC does not
automatically allocate a type field to files if one is not specified.)
You may find it useful to add your own type fields - a popular
convention is to use the type fields '.BAS' to identify BASIC files
and '.BIN' to identify CODE files ('.BIN' being short for binary). If
you think this is a good idea, then the previous example program could
be saved using...
SAVE "squares.bas"
The characters '*' and '?' have a special meaning to +3 BASIC, and
cannot be used in a filename for LOAD and SAVE. There are, however,
file commands in which '*' and '?' can be used, and these will be
discussed later.
Here are some examples of valid filenames...
z
squares
m:picture.bin
a:fred
13a:hello
0M:CAPITALS
test.bas
philip
glass.mus
a:a.a
Here are some illegal filenames (and reasons why)...
pac man (must not contain any spaces)
(test) (must not contains brackets)
/<>-+=!& (must not contain any of these characters)
excessive (more than 8 characters long)
.bas (has no name field)
later... (only one dot allowed)
7:dubious (if user number is specified, then filename
must also contain drive letter - e.g.
'7a:dubious')
Disk catalog
You may have spotted the fact that we have now saved the same program
twice with two different names ('SQUARES' and 'SQUARES.BAS'). It would
be nice to be able to check what has been saved on a particular disk,
and this is where the CAT command comes in. CAT displays a catalog of
what you have stored on a disk.
Press ENTER then type in...
CAT
The +3 will take a quick look at the disk (the read/write indicator
lamp will come on briefly), and will display a list of the disk's
contents on the screen. The list is sorted into alphanumerical order
and each file is followed by an indication of its size to the nearest
number of kilobytes (rounded up). At the end of the list, the amount
of free space on the disk is also displayed.
CAT (on its own) is the simplest form of the command. If you wanted to
list all the files on a different drive (e.g. drive M:), you would
use...
CAT "m:"
When CAT is followed by a filename containing just a drive letter,
i.e. 'A:', 'B:' or 'M:' (including the colon), all the files on the
nominated drive will be listed. CAT on its own gave a list of the
files on drive A:, this is because A: is the current default drive.
You will remember that LOAD or SAVE followed by a drive letter will
make that drive the current default. So...
LOAD "m:"
CAT
...will also list all the files on drive M:. This isn't quite the same
as 'CAT "m:"', because now the default drive has been left as M:.
Change it back to A: before going further.
We will now save several copies of our simple example program using
different names, so that you will be able to see what the various forms
of the CAT command will produce. So far the disk should contains
'SQUARES' and 'SQUARES.BAS'. If either of these weren't listed with
the above CAT command, add their name to the list below. Type the
following...
SAVE "fred"
SAVE "fat"
SAVE "santa.bin"
SAVE "trepur.bak"
SAVE "cliff.cjl"
SAVE "sausages.bas"
Don't worry about cluttering up the disk with lots of copies of the
same thing - you'll be shown how files can be erased later.
Wildcards
If a disk has a large number of files, it is often desirable to
selectively list only those of interest. The +3 caters for this. If,
for example, you wished to list only those files that ended in '.BAS'
you would use:
CAT "*.bas"
The asterisk character '*' is what's known as a wildcard. When a
filename, perhaps containing a wildcard, is specified, CAT will list
only the files that match the 'specification' given. When the '*'
wildcard is used (in either the name field or the type field) it means
'any character from here to the end of this field'. So, in the above
command, we want CAT to display any files that have any characters in
their name field and the letters 'BAS' in their type field. If there
are no files on the disk that match the specification, the report 'No
files found' will be displayed (followed by the amount of free space).
If you give a file specification of '*.*' (i.e. 'CAT "*.*"') or no
specification at all, (i.e. CAT) and the report 'No files found' is
displayed, then this means that the disk is empty. An empty disk in
drive A: or B: will have a free space value of 173K (this value may be
different for disks from other types of computer). An empty drive M:
will usually have 58K free. If you catalog a disk containing a
commercial program (such as a game), it might appear to have no files
on it but very little space free. This is a protection measure taken
by the software writers to prevent illicit copying, and shouldn't
cause any concern.
If we use...
CAT "s*.bas"
...then all files that begin with the letter 'S' and then have any
characters whatsoever between the 'S' and the end of the name field,
followed by a type field of 'BAS', will be shown. Files with the names
'SQUARES.BAS', 'SAUSAGE.BAS', 'SUPER.BAS' would all be listed, but
'SQUARES.BIN', 'TOAST.BAS' and 'SQUARES' would not.
The '*' wildcard can also be used in the type field of a filename
(note, however, that you cannot use it in place of the user number or
drive letter). If we wanted to list all files that had 'SQUARES' as
their name field and anything as their type field, we would use...
CAT "squares.*"
Similarly, if we wanted to list all the files that began with a letter
'S' and had a type field that began with the letter 'B' we would
use...
CAT "s*.b*"
When we type CAT (on its own), we want to list all files on a disk.
Therefore, CAT is just a shorthand way of saying...
CAT "*.*"
From the above you will notice that the '*' wildcard can only be used
as the last character in a field, and it is used to mean 'I don't care
what other characters are present between here and the end of this
field'. Sometimes, however, you may want to specify a group of files
but need to be a little more discerning. This is when you use the '?'
question mark wildcard (in either the name field or the type field).
The '?' wildcard means 'I don't mind what character happens to be in
this specific position'.
Therefore, if we used the command...
CAT "?at"
...then the files listed would be all those that are three characters
long, ending in 'AT', but we don't mind what character is in the first
position. Thus files such as 'CAT', 'SAT', 'MAT' and 'FAT' would be
listed, but 'CAR', 'CATTLE' and 'AT' would not. Unlike the '*'
, '?' wildcards can be used in place of any of the 8
characters of the name field and the 3 characters of the type field.
There is no limit to the number of question marks you can use (other
than the 8 and 3 limits of the filename field lengths).
Valid file specifications containing '?' wildcards include...
?.bas (one letter name with a type field of 'BAS')
s?uares.* (specific files whose second character doesn't matter,
with any type field)
ca??.?t? (files beginning 'CA' with four characters in the name
field, and with a type field of 3 characters whose
second letter is 'T')
????????.??? (exactly the same as '*.*')
If you have a printer connected to your +3, you may find it useful to
print-out the files listed by CAT. You can do this by directing the
output from CAT to stream 3 (streams are explained in part 22 of this
chapter). The command to do this is...
CAT #3
If you only want some of the files printed-out, you can also include a
file specification in exactly the same way as before. For example...
CAT #3,"a:*.bas"
(The above 'CAT #3' commands will not work unless a printer is
connected to the +3 and is on line. To abandon, press BREAK.)
Any form of the CAT command may also end with the word EXP, for
example, 'CAT "a:" EXP'. The EXP is short for expanded, and as the
name might suggest, gives you a little more information about the
attributes of the files on a disk. Not only will the expanded catalog
display system files but also it will indicate whether files are set
to write protected mode, archive mode or system status (these terms
are explained in the section ahead entitled 'File attributes').
(There is one other specialist use for the CAT command, and this will
be dealt with in the section ahead entitled 'Tape catalog'.)
Now that you have successfully saved a program to drive A:, you can
happily switch off or reset the +3, or start a NEW program, knowing
that you could always load in the saved program if you needed it.
Remember - there is a difference between resetting the +3 and using
the NEW command - if you reset, all the +3's memory (RAM) will be
cleared. This includes any files you may have saved on drive M:. When
you use NEW, however, any files on drive M: will remain intact. As we
have saved the program on the disk in drive A:, you can go ahead and
press the RESET button, then release it. The usual opening menu will
be displayed. Select '+3 BASIC' then type the command...
LOAD "squares"
The LOAD command reads in a new program (and variables) from disk, and
then deletes any program (and variables) previously in the memory. (If
the program that you specified to load is not on the disk, then any
program currently in the memory is not deleted.) Just like SAVE, the
LOAD command must be given a filename whose name field is at least one
character long. If you have been used to a tape machine in the past,
then you may have used 'LOAD ""' to mean 'load the next program on the
tape'. The concept of a 'next program' on disk does not exist, so if
you don't specify a filename, the disk system won't know what to load
and will report an error. If you can't remember what name you saved a
file under, use CAT to check what's on the disk (this is why it's a
good idea to save programs on disk using 'mnemonic' names (names that
remind you what they contain) - e.g. it is more obvious what sort of
program a file named 'TENNIS.BAS' contains compared to one simply
named 'T').
There is a short cut for loading programs (such as games) that have
been specially set up - you can select the 'Loader' option from the
opening menu. This option, when selected, attempts to load and run
programs. First of all, it looks for a program called '*' on the disk.
If this exists, then it will be loaded and run. The program has to be
a machine code program saved in a particular fashion (as BASIC can't
use '*' as a filename for SAVE), and is, therefore, only for use on
commercial software or by those who understand machine code.
If '*' can't be found, the +3 will then look for a file called 'DISK'.
This can be a BASIC program that you've previously written and saved,
so if the 'Loader' option finds a program called 'DISK', it will load
it and wait for the next operation.
At this point, pressing ENTER will just load the program again.
If you wish to run or edit the program after it has loaded, first
press the cursor down key once, then ENTER. This selects the '+3
BASIC' option from the opening menu.
If there isn't a program called 'DISK' on the disk (or if the +3
detects that there isn't a disk in the disk drive), then the computer
will try to load a program from tape, displaying the message...
Insert tape and press PLAY
To cancel - press BREAK twice
This is the recommended method for loading Spectrum +3 (Spectrum +2
and Spectrum 128) software from tape (see chapter 4).
As previously mentioned, LOAD deletes the old program and variables in
the +3 whenever it loads in the new ones from disk. However, there is
another command - MERGE, which is similar to LOAD but it only deletes
an old program line or variable if there is a new one with the same
line number or name. Clear the program memory using the NEW command,
then type in the 'dice' program from part 11 of this chapter and SAVE
it onto disk, using...
SAVE "dice"
Use NEW to clear the program memory again, then enter and run the
following program...
1 PRINT 1
2 PRINT 2
10 PRINT 10
20 LET x=20
Now type in...
MERGE "dice"
If you then LIST the program, you will see that lines 1 and 2 have
survived, but lines 10 and 20 have been overwritten by those from the
dice program. Note that the value of the variable 'x' has also
survived (try 'PRINT x').
You have now seen simple forms of five of the commands that work in
conjunction with disk:
FORMAT Prepares brand new disks so that programs can be saved
onto them. FORMAT can be used to completely erase
everything on a disk that has already been used.
SAVE Stores the program and variables onto a disk.
LOAD Clears the computer of all its program and variables,
and replaces them with new ones read in from disk.
MERGE Similar to LOAD except that it does not clear the old
program lines and variables unless it has to (because
they are the same as those being loaded in from disk).
CAT Displays a list of the files contained on a disk.
A variant on SAVE takes the form...
SAVE filename LINE number
A program which is saved using this command, is stored in such a way
that when it is loaded, it automatically jumps to the line with the
given number, then runs itself.
Use NEW to clear the program memory then type in the following...
10 PRINT "program running"
20 PLAY "cdefgabC"
Now save this program using the command...
SAVE "disk" LINE 10
Now reset the +3, and when the main menu appears, ensure that the disk
(with the above program on it) is in the drive then press the ENTER
key. This will select the 'Loader' option which searches for a file on
the disk called 'DISK'. When it finds the simple example program you
just saved, it will load it, and as it was saved using a LINE
parameter, it will automatically start running (from line 10).
At this point, pressing ENTER will load and run the program again.
If you wish to edit the program after it has run, press the cursor
down key once, then ENTER. This selects the +3 BASIC option from the
opening menu.
Note that if you load a program called 'DISK' which doesn't
automatically run (using the 'Loader' option from the opening menu),
then you will have to select the +3 BASIC option (after the program
has loaded) before you can run it or edit it.
So far, the only kinds of information we have stored on disk have been
programs (together with their variables). There are also two other
kinds of information, called arrays and bytes.
You can save arrays on disk using the keyword DATA in a SAVE
statement...
SAVE filename DATA array name ()
...where filename is the name that the information will have on disk
and works in exactly the same way as when you save a program.
The array name specified the array you want to save, so it is just a
letter (or a letter followed by '$'). Remember to put the brackets
'()' after the array name.
Be clear about the separate roles of filename and array name. If you
say (for instance)...
SAVE "bloggs" DATA b ()
...then SAVE takes the array 'b()' from the computer and stores it on
disk under the name 'BLOGGS'.
The command...
LOAD "bloggs" DATA b ()
...sees if it is possible to load the array (i.e. if there is room for
it in the computer), then if so, deletes any already existing array
called 'b()' and loads in the array 'BLOGGS' from disk, calling it
'b()' in the computer.
You cannot use MERGE with saved arrays.
You can save character (string) arrays in exactly the same way.
However, note that when you load in a character array, it will delete
not only any previous character array with the same name, but also any
simple string variable with the same name.
When dealing with a large amount of data you may find it useful to use
the SAVE...DATA option and the LOAD...DATA option to and from drive
M:. Once saved on drive M: the space previously used by an array can
be re-used. Using drive M: will mean that saving and loading are very
fast.
Byte storage is used for pieces of information without any reference
to what the information is used for - it could be a screen display, or
perhaps some user-defined graphics, or just something you have made up
for yourself. It is specified using the word CODE, as in...
SAVE "picture.bin" CODE 16384,6912
The unit of storage in memory is the byte (a number between 0 and
255), and each byte has an address (which is a number between 0 and
65535). The first number after CODE is the address of the first byte
to be stored on disk; the second number is the amount of bytes to be
stored. In our case, '16384' is the address of the first byte in the
file (which contains the screen display), and '6912' is the amount of
bytes in it, so we are saving an actual copy of the screen display
onto disk. Try the above SAVE command. (You don't have to save the
bytes using the name 'PICTURE.BIN' - it's merely a convenient reminder
of what's on the disk.)
To load it back, use...
LOAD "picture.bin" CODE
You can put parameters after CODE in the form...
LOAD filename CODE start,length
Here, the length parameter is used as a safety measure - when the
computer attempts to load the bytes from disk, it will check the
length and refuse to load the bytes if there are more than specified
(thereby safeguarding against the extra bytes accidentally overwriting
an area of memory that you wished to preserve). In such a case, the
report 'Code length error' is displayed. (Anyone using a cassette unit
under 48 BASIC should note that the above error will display a
different report: 'R Tape loading error'.
If you leave out the length parameter, the +3 will read in the bytes
however many there are.
The start parameter shows the address where the first byte is to be
loaded back to - this can be different from the address it was saved
from, though if they are the same, then you can leave out the start
parameter in the LOAD statement.
'CODE 16384,6912' is such a useful area of memory (the screen display)
to save and load, that a special function (SCREEN$) has been provided
to represent it, so you can type (for example)...
SAVE "picture.bin" SCREEN$
...or...
LOAD "picture.bin" SCREEN$
Automatic back-ups
If you have saved one or two things on a disk and then you save
something with a filename that has already been used, what will
happen? Well, each time you save a program, the disk system checks to
see if the filename you specify has already been used. If it has, the
existing copy on disk is given a new filename before the information
you have asked to save is stored. The new name given to the existing
file has the same name field but its type field will always be '.BAK'
(short for backup).
If a '.BAK' version of the file already exists, then that will be lost
in preference to the new '.BAK' file. This means that as you save
successive versions of a program with the same name the previous copy
will still be there in a file called filename.BAK. So, if you make a
serious programming error and inadvertently save the program, you can
delete the newest version and rename the '.BAK' file to the original
filename. The next section shows you how to do this; but first,
type...
SAVE "a:squares"
...to save the program using the filename 'SQUARES' yet again.
Deleting and renaming files
Files can be deleted from a disk using the ERASE command. This should
be followed by a filename that specifies which file or files are to be
deleted. Just like CAT, you can use the wildcards '*' and '?' to
identify a group of files, or you can specify the name in full if you
only want to get rid of one particular file. If you specify a single
filename, that file will immediately be erased from the disk - so take
care. If you specify a group of files (by including '*' or '?'), BASIC
will ask you to confirm that you really mean to delete this group of
files. Typing 'Y' will make the deletion process continue, so if you
have made a mistake, type 'N'.
If, for example, you wanted to delete a file from drive M: called
'FRED.BAS', you would use...
ERASE "m:fred.bas"
If drive M: has already been set as the default drive, then you don't
need to include the M: at the start of the filename. It doesn't hurt
to include the drive letter anyway, and with as powerful a command as
ERASE, you might feel safer if you do. To erase all the files on drive
B: you would use...
ERASE "b:*.*"
Before doing this, BASIC will ask for confirmation...
Erase b:*.* ? (Y/N)
...and assuming that you really mean to wipe all the files from the
disk in drive B:, you would then type 'Y'.
If you ask to delete a single file (or a group of files using the
wildcards '*' and '?') and there are no files on the disk that match
the specification, then the report 'File not found' will be displayed.
Note that ERASE followed by just a drive letter (e.g. 'ERASE "m:"')
will erase all files on the specified drive without asking for
confirmation. Be careful, therefore, not to enter this form of the
command unless you really mean to delete everything! (The ERASE
process will stop and report an error if a write protected disk or
file is detected.)
The disk you have been using up to now has many copies of the simple
'SQUARES' program (saved under different names) on it. This is a waste
of space so you might as well erase those that aren't needed. What you
want to do in effect is erase everything except 'SQUARES' (though
there is no simple way to do this). However, some of the different
files have the same letters in common, so you may be able to use
various forms of '*' and '?' specifications to cur down the amount of
typing. See if you can work out the fewest number of ERASE commands to
erase all files other than 'SQUARES'.
Once a file has been saved, it can be given a new names using the MOVE
command. For example, if there is a file on drive M: called 'SQUARES'
that you would like to call 'BLOCKS', its name could be changed as
follows (first we make sure there is a file called 'SQUARES' on drive
M:). Type...
SAVE "m:squares"
MOVE "m:squares" TO "m:blocks"
CAT "m:"
Imagine we have saved a file called 'FRED', and then after working on
it and saving a new version with the same name, realised that we had
made a terrible mistake and would like to recover the last version.
This would be possible using the commands...
ERASE "fred"
MOVE "fred.bak" TO "fred"
Unlike ERASE, you cannot include the wildcards '*' or '?' when
renaming files.
MOVE will take into account the current default drive so the filename
doesn't necessarily have to contain a drive letter. Note, however,
that it is not possible to use MOVE to rename files between different
drives. The command...
MOVE "a:fred" TO "b:eric"
...(for example) will fail with the error 'No rename between drives'
reported. Instead, you can use the COPY command (explained ahead)
followed by ERASE to achieve the desired result.
File attributes
MOVE has another use besides renaming files. It can also be used to
change the attributes of a file. Attributes are bits of information
associated with a file that tell you (and the computer) a little more
about it.
There are three attributes that can be changed. The most useful
attribute is write protection. Once a file's write protection
attribute has been set, it will not be possible to erase it (or save a
file with the same name) until you remove the write protection. It
behaves a little like the write protect hole on the disk, but works
just on individual files. Unlike the write protect hole, however, it
offers no protection against FORMAT, which erases everything on a
disk, regardless of attributes. You can set a file's write protection
attribute to on with a command such as...
MOVE "squares" to "+p"
The letter 'P' is short for protection (against overwriting). If you
now try to use the command...
ERASE "squares"
...you will receive an error report saying 'File is read only'.
To switch write protection off, use...
MOVE "squares" TO "-p"
...and you'll be able to erase the file as before.
In all the MOVE commands that change attributes, '+' means switch it
on, and '-' means switch it off.
When you are using MOVE to change attributes, the filename can include
the wildcards '*' and '?'. So, to make all the files on drive M: write
protected, you would use...
MOVE "m:*.*" to "+p"
As always, the drive letter can be omitted if it is the current
default drive.
You can repeatedly switch attributes on or off without causing an
error, so if you set write protect on a file that has already got
write protection, it will just stay protected.
The second attribute that can be changed is known as the system status
attribute. This is really provided just to be compatible with other
CP/M based computers, however, if you do set a file's system attribute
to on, then you will notice that the file no longer appears in the
list of files when you use CAT. The system status attribute is
identified by '+S' (or '-S') in the MOVE command. If you use the
expanded catalog, (i.e. 'CAT EXP'), all the files will then be listed
including system status files (which are followed by the letters
'SYS'). You may also notice that any files that are write protected
are followed by the letters 'PROT'. You can use the system attribute
to remove files from a catalog if they would otherwise just clutter
things up.
Bear in mind that you cannot have two files on the same disk with the
same filename and different system status attributes; so if you try to
create or copy a file onto a disk where a file of that already exists
(but is hidden from CAT), then the previous file will be deleted.
The final attribute you can change is known as the archive
attribute. In an expanded catalog it shows up as 'ARC', and is
identified by '+A' (or '-A') in the MOVE command. On the +3, the
archive attribute is of no practical use and is only provided for file
compatibility with CP/M based computers.
Here are some attribute-setting MOVE commands. See if you can predict
what they will do...
MOVE "*.*" TO "+p"
MOVE "*.bas" TO "-s"
MOVE "s???.*" TO "+a"
MOVE "m:?.?" TO "-p"
If you try to use any letter other than 'A', 'S' or 'P' in setting or
resetting attributes, or if the 'attribute string' is not two
characters long, then you will receive the report 'Invalid attribute'.
Quite often, a situation will arise when you would like to make a copy
of one of your files, (to give to a friend perhaps, or to put it on
drive M: so that it can be accessed quicker). The COPY command can be
used to copy from one drive to another and even to make complete
copies of disks. The very simplest form of the COPY command will look
something like this...
COPY "a:fred" TO "m:"
This means, put a copy of the contents of the file called 'FRED' (which
is presently on drive A:) onto drive M:. As no destination name has
been specified (after M:), the new file will also be called 'FRED'.
The name before the word TO is known as the source filename, and the
name after TO is the destination filename.
The command...
COPY "fred" TO "eric"
...will take the contents of a file called 'FRED' on the default drive
and copy it to a file called 'ERIC', also on the default drive. The
files 'FRED' and 'ERIC' then contain the same information.
You cannot copy one file to another with the same name and on the same
drive. Trying to do so will result in the error report 'File already
exists' (or possibly 'File already in use').
The source filename for copying from can include the wildcards '*' and
'?', however, in this case the destination filename has to be just a
drive letter. So, for example...
COPY "a:*.ovl" TO "m:"
...will work (assuming that there are some files on drive A: that
match this specification), and transfers all files on A: with a '.OVL'
type field onto drive M:. However, the command...
COPY "a:*.bas" TO "m:*.bin"
...will fail with the error report 'Destination cannot be wild'.
The COPY command does not copy any attribute information associated
with a file; you have to set any attributes you require on the new
file after copying.
COPY will always list the files it is copying in two columns. This
will allow you to check that any wildcard specification you use
encompasses all the files that you were intending to copy.
After copying, a report will appear to let you know many files were
copied. (If you were copying a group of files, this may be useful to
check that you have indeed copied all the files you intended to.)
There is a special format of the COPY command as follows...
COPY "a:" TO "b:"
...which will perform a complete 'sector by sector' copy of the disk
in drive A: to an already formatted disk in drive B:. Anything already
stored on the disk in drive B: will be lost - so, if there are only a
few files on the source disk to be copied, it may be quicker to use...
COPY "a:*.*" TO "b:"
Even if you have only one drive (A:), you can use the fact that the
single mechanism can be used as if it were drive A: or drive B:. For
example, suppose you have a single drive system and want to copy a
couple of files (that both end in '.BAS') from one disk to
another. Put the source disk in the drive and type...
COPY "a:*.bas" to "b:"
Once the +3 has read part of the first file that ends in '.BAS', it
will ask you to...
Please put in the disk for B: into
the drive then press any key
Simply follow this instruction. After the +3 has written the
information onto the 'drive B:' disk, it will ask you to...
Please put in the disk for A: into
the drive then press any key
This process of swapping between disks will go on until all files have
been copied. Because the COPY command will try to use any free space
on drive M:, it is a good idea to clear drive M: (if possible) before
doing a lot of copying (as this can reduce the number of disk swaps
needed).
As well as copying files between drives, COPY can also be used to copy
files to the screen or to a printer (if connected). The command...
COPY "words.txt" TO SCREEN$
...will display the contents of a file on the default drive called
'WORDS.TXT'. Any control characters (except carriage returns) will be
filtered out. This command cannot really be used to look at BASIC
program files as they contain various control codes. Its main use will
be to inspect the contents of ASCII text files, such as those produced
by a word processor.
The command...
COPY "words.txt" TO LPRINT
...is similar to the above, but this time the contents of the file
will be sent to the printer. In this case, however, control codes will
be sent to the printer. If you have set the print output to be via the
RS232 with tokens unexpanded (using 'FORMAT LPRINT "R";"U"'), then
this command can be used to 'export' files to other computers. Once
again, this command cannot be used for BASIC programs - it is intended
for sending ASCII text files only.
People writing machine code programs may find it easier to do so on a
larger development machine. However, the files produced by this method
will probably not be recognised by the +3, as BASIC expects to find a
128 byte header at the start of each file which contains information
used by the LOAD command. However, once a binary file has been
produced on a +3 formatted disk, it can have a header of the correct
type put on it using a command such as...
COPY "game.com" TO SPECTRUM FORMAT
This will produce a new file on the same drive, having the same name
field but with a type field of '.HED' (short for headed). In the above
example, a new file called 'GAME.HED' will be created, and it will be
written to the default drive (as no drive letter was specified).
Obviously this command will only be of use for machine code
files. Headed files produced in this way will have the length part in
their header set to the correct value and the type part set to be a
CODE file. However, BASIC cannot know what address the file should be
loaded to, so the load address should be specified when the
'LOAD...CODE' command is used. For example, if the above program had
been assembled to execute at 7000h (the 'h' denotes a hexadecimal
number) or 28672 decimal, then the headed file could be loaded with
the command...
LOAD "game.hed" CODE 28672
As SCREEN$ files are just another type of CODE file, this technique
can be used to 'import' screens designed on another machine, though
they obviously wouldn't make much sense unless they had been tailored
to fit the +3's size and layout.
The RAMdisk
You may have been wondering what point there is in storing information
in the RAMdisk (drive M:) as it will be lost once the +3 is switched
off. Well, perhaps the most obvious use of drive M: is to store chunks
of BASIC program (or routines) which can be merged (using 'MERGE
"M:filename"') into a smaller program, in sequence. This makes it
possible to write about 90K of BASIC program, and hold it in the +3
(though to do this, the program structure has to be well defined).
You can keep the various routines on a 3 inch disk and use COPY to put
them into drive M: before you run the program. The benefit of doing
this is that drive M: is much quicker to access than the mechanical
drives (A: and B:). The mechanical drives, however, can hold much more
data, so you might like to evolve a system using both disk and
RAMdisk. Careful design and planning will repay itself many times over
it terms of speed and performance.
One of the more interesting uses of the RAMdisk is in animation, where
a series of pictures can be defined by a 'slow' BASIC program, stored
in drive M:, then called back to the screen at high speed. The
following program offers a taste of this. Doubtless you can do
better...
10 INK 5: PAPER 0: BORDER 0: CLS
20 FOR f=1 TO 10
30 CIRCLE f*20,150,f
40 SAVE "m:ball"+ STR$ (f) CODE 16384,2048
50 CLS
60 NEXT f
70 FOR f=1 TO 10
80 LOAD "m:ball"+ STR$ (f) CODE
90 NEXT f
100 BEEP 0.01, 0.01
110 FOR f=9 TO 2 STEP -1
120 LOAD "m:ball"+ STR$ (f) CODE
130 NEXT f
140 BEEP 0.01, 0.01
150 GO TO 70
Before running the program, always make sure that drive M: is empty.
If it isn't, first type 'ERASE "m:*.*"' (typing 'Y' at the '(Y/N)'
prompt), then RUN.
Note that in line 40 of this program, the two numbers following CODE
are the address in memory of the start of the screen ('16384') and the
length of the top third of it ('2048'). By saving and loading only the
top third, the overall speed is maintained.
Tape operations
(See chapter 10 (Peripherals for your +3) for details on how to
connect a cassette unit to your +3.)
Much of what has been said in this section about the use of LOAD, SAVE
and MERGE on disk will apply equally to tape (if you have connected a
cassette unit to the +3). However, the commands FORMAT, COPY, MOVE,
CAT and ERASE do not apply on tape (although there is a special form
of CAT that can be used - described in the section ahead entitled
'Tape catalog').
As you will already know, when you first switch on the +3, the default
drive for all file operations is set to drive A:. This means that if
you use CAT, ERASE, LOAD, SAVE, etc. without specifying a drive
letter, then +3 BASIC will perform the operation on drive A:. You will
also know that the default disk can be changed using either...
LOAD "drive letter:"
...or...
SAVE "drive letter:"
...where drive letter is either 'A:', 'B:' or 'M:' (which must include
the colon). In fact you can also use 'T:' as a drive letter, but only
in this one special form of the LOAD and SAVE command...
LOAD "t:"
After 'LOAD "t:"', all subsequent LOAD and MERGE operations are
performed to tape (until changed back to disk by, for example, 'LOAD
"a:"'). Similarly, if you use...
SAVE "t:"
...then all future SAVE operations will be performed to tape (again,
until changed back to disk by, for example, 'SAVE "a:"'). Unlike 'A:',
'B:' or 'M:', when you use 'T:' as the drive letter, it will change
only future LOAD, SAVE and MERGE commands. The default drive used for
MOVE, COPY, CAT and ERASE will stay the same as it was before (as
these commands have no relevance to tape).
If all this sounds a little complicated, a few examples might help to
make it a little clearer. Assuming you have just switched on (or
reset) the +3, the default for all operations will be A:. So if you
now type...
SAVE "m:"
...then the default drive for all subsequent operations will be set to
drive M: (this is exactly the same as if the command 'LOAD "m:"' had
been used). Using the command...
LOAD "b:"
...will then set the default drive for all operations to drive B:. For
this sort of thing, LOAD and SAVE operate in exactly the same way.
If we now use the command...
SAVE "t:"
...this will perform all future SAVE operations to tape, but all other
commands will still default to drive B:. Using the command...
LOAD "t:"
...will also perform all future LOAD and MERGE operations to tape;
however, the default drive for all disk-only commands will still be
drive B:.
Finally, using the command...
SAVE "a:"
...will perform all future SAVE operations and all disk operations
(except LOAD and MERGE) to drive A:. LOAD and MERGE will still be from
tape, however.
Let's try to save our simple 'squares' program onto tape. Reset the +3
then type...
LOAD "squares"
This should load in the program that we saved earlier. If you press
ENTER, the program will be listed as follows...
10 POKE 22527+ RND *704, RND *127
20 GO TO 10
This is the program that you are now going to save to tape. Any
standard tape should work, although low noise tapes are preferable.
Type in the following...
SAVE "t:"
SAVE "squares"
This will save the program onto tape using the filename 'SQUARES'.
When saving files on tape, you are allowed up to ten characters in the
name. Unlike disk, you can use any characters you like and the name
can include spaces.
The +3 will display the message...
Press REC & PLAY, then any key.
We shall first go through a 'dry run' so that you can see what will
happen when we actually do save the program later. This time,
therefore, don't press REC and PLAY on your cassette unit - just press
a key on the +3 (for example ENTER) and watch the border around the
screen display. You will see patterns of coloured horizontal stripes
as follows:
Five seconds of red and cyan stripes moving slowly upwards, followed
by a very short burst of blue and yellow stripes.
A short pause.
Two seconds of the red and cyan stripes again, followed by another
short burst of blue and yellow stripes.
While the stripes appear on the screen, you can also hear the 'sound'
of the data through your TV's speaker.
Keep trying out the above SAVE command (without actually operating
your cassette unit) until you can recognise these patterns. What's
actually happening is that the information is being saved in two
blocks and both blocks have a 'lead-in' (which corresponds to the red
and cyan stripes) followed by the information itself (which
corresponds to the blue and yellow stripes). The first block is a
preliminary one containing the name and various other bits of
information about the program, and the second is the program itself
together with any variables present. The pause between them is just a
gap.
Now let's actually save the program onto tape:
1. Wind the tape to an area that is either blank, or that you are
prepared to overwrite.
2. Type...
SAVE "squares"
3. Follow the instructions on the screen, i.e....
Press REC & PLAY, then any key.
4. Watch the screen as before. When the +3 has finished (with the
report '0 OK'), stop the tape.
Whenever you save a program to tape, before clearing the saved program
from the +3's memory, you should always make sure that the program was
correctly saved. You can check the signal on the tape against the
program in the memory using the VERIFY command (this command isn't
used on disk, as disks are not prone to the same sorts of errors as
tapes are):
1. Rewind the tape to just before the point at which you saved the
program.
2. Type...
VERIFY "squares"
Play the tape. The border will alternate between red and cyan until
the +3 finds the program that you specified, then you will see the
same pattern as you did when you saved the program. During the pause
between the blocks, the message 'Program: squares' will be displayed
on the screen. (When the +3 is searching for something on tape, it
displays the name of everything it comes across.) If, after the
pattern has appeared, the +3 displays the report '0 OK', then your
program is safely stored on tape and you can skip to the section ahead
entitled 'Verified OK'. Otherwise, something has gone wrong - take the
following steps to find out what.
If the program name has not been displayed, then either the program
was not saved properly in the first place, or it was but was not 'read
back' properly. You need to find out which. To see if it was saved
properly, rewind the tape to just before the point at which you saved
the program, then play it back while listening to the TV's speaker.
The (red and cyan) lead-in should produce a clear, steady high pitched
note, while the (blue and yellow) information part gives a much
harsher screech.
If you do not hear these noises, then the program was probably not
saved. Check that you were not trying to save the program onto the
plastic leader at the beginning of the tape. When you have checked
this, try saving again.
If you can hear the sounds as described, then SAVE was probably
alright and your problem is with reading back.
It could be that you mistyped the program name when you saved it (in
which case when the +3 finds the program it will display the mistyped
name on the screen). On the other hand, perhaps you mistyped the
program name when you verified it, in which case the +3 will ignore
the correctly saved program and carry on looking for the wrong name,
flashing red and cyan as it goes.
If there is a genuine mistake on the tape, then the +3 will display
the report 'R Tape loading error' which means in this case that it
failed to verify the program. Note that a slight fault on the tape
itself (which might be almost inaudible with music) can wreak havoc
with a computer program. Try saving the program again, perhaps on a
different part of the tape (or a different tape altogether).
Verified OK
Now let us suppose that you have saved the program and successfully
verified it. Loading it back into the memory is just a matter of
typing...
LOAD "squares"
(Since the program verified properly, you should have no problem
loading it.)
LOAD deletes the old program (and variables) in the memory when it
loads in the new one from tape.
Once a program has been loaded, the report '0 OK' will appear. The
program can then be run or edited.
As mentioned in chapter 4, it is possible to buy pre-recorded programs
(software) on tape. They must be specially written for the ZX Spectrum
range (i.e. the Spectrum, the Spectrum +, the Spectrum 128, the
Spectrum +2 or the Spectrum +3). Different makes and models of
computer have different ways of storing programs, so they cannot use
each other's tapes.
If your tape has more than one program stored on the same side, then
each program will have a name. You can choose the program you wish to
load using the LOAD command - for instance, if the one you want is
called 'HELICOPTER', you could type...
LOAD "helicopter"
The command 'LOAD ""' means 'load the first program that the +3 comes
across on tape'. This can be very useful if you cannot remember the
name that you saved the program under! (Remember that this only works
on tape - normally you cannot specify a blank filename.)
When there is no disk in drive A: (or the disk contains no file called
'*' or 'DISK'), then the option 'Loader' from the opening menu has the
same action as 'LOAD ""' from tape, and is much quicker to use -
simply switch on (or reset) the +3 and press ENTER.
MERGE will operate in a similar way to that described for disk except,
of course, that on tape you can use 'MERGE ""' to mean 'merge the next
file on tape'. Filenames in a MERGE command may conform to the less
stringent limits for tape (i.e. any combination of 10 characters
including spaces).
If you have BASIC programs saved on tape (perhaps because you owned a
previous Spectrum model), you will probably want to transfer them to
disk to gain the advantage of faster loading. This should be
relatively straightforward. Just use...
LOAD "t:"
SAVE "a:"
...then for each BASIC file on the tape, use...
LOAD ""
...which will load the next file from the tape into the +3's program
memory. Once loaded, the file can be saved out to disk using...
SAVE filename
Remember that files on disk must be given a filename which conforms to
the limitations outlined at the beginning of this section.
If the BASIC programs have been saved with an automatic execution
LINE, you will find that attempting to LOAD them will also run them.
Obviously you don't want this so, for each program you wish to load,
reset the computer, select '+3 BASIC' and type...
MERGE ""
...(rather than 'LOAD ""').
If you have saved data (numeric or string) arrays, it should be an
equally simple matter to LOAD them into memory from tape, then SAVE
them to disk.
The only file types that may cause difficulty when you want to
transfer them from tape to disk are CODE (and SCREEN$) files. To be
able to transfer a file of this type you need to know at least two
things about it.
1. The address it was saved from.
2. How many bytes it contains.
Tape catalog
This is where the final form of the CAT command comes in. If the file
specification given is simply 'T:', a special form of the CAT command
comes into action. After you type...
CAT "t:"
...the +3 will wait for you to play a tape (the 'CAT "t:"' operation
can be abandoned by pressing BREAK). When the +3 finds a header on
tape it will display the information (in the same form it was saved).
This means that there will be a ten character filename in inverted
commas. What follows the filename will depend upon the type of file -
if it was a BASIC program, the word '(BASIC)' will be displayed. If a
LINE parameter was specified when the file was saved, this will also
be shown. If the file holds data, then the word DATA followed by the
array name will be displayed, and finally, if the file was saved using
CODE (or SCREEN$, which is really just 'CODE 16384,6912'), the word
CODE will be printed followed by the start address and length that
were specified when the file was saved.
Here is a sample display resulting from a 'CAT "t:"' command, which
may make this a little clearer...
"simple " (BASIC)
"execute " LINE 10 (BASIC)
"numbers " DATA f()
"words " DATA c$()
"m/c " CODE 30000,12345
"picture " CODE 16384,6912
The last item was, in fact, saved using...
SAVE "picture" SCREEN$
Just like the other forms of CAT, its output can be directed to a
printer using stream 3, i.e....
CAT #3,"t:"
(Streams are explained in part 22 of this chapter.) Note that the
above 'CAT #3,"t:"' command will not work unless a printer is
connected to the +3 and is on-line. To abandon, press BREAK.
From the above it can be seen that if you have loaded (using 'MERGE
""') a program containing an execution LINE parameter, the 'CAT "t:"'
display will identify that line number for you. You may then wish to
save that program to disk using...
SAVE filename LINE line number
...so that the disk version of that program runs itself automatically.
It is the values for the CODE files that you will probably find most
useful from the 'CAT "t:"' display. Either note them down or print
them out. Then rewind the tape so it just before the header that has
been read. Type...
CLEAR start-1
...where start is the value printed for the start address. Now type...
LOAD "" CODE
When the file has loaded into memory and the '0 OK' report appears,
the file can be saved to disk using...
SAVE filename CODE start,length
This technique is only intended for transferring your own code files
(where you may have forgotten what start and length values were used
when you saved them). Note that using this method to copy commercial
software may be a breach of copyright - check with the software author
first.
There are several reasons why this simple scheme may not work:
1. The code, when loaded would overwrite some of the system variables
(in the range 23296 (5B00h) to 23755 (5CC6h)). This upper address
limit may vary - it is the value held in the system variable PROG (see
part 25 of this chapter).
2. Attempting to load code that has no header (or that is protected in
some other way) probably won't even produce any output from 'CAT "t:"'
and you certainly won't be able to use the BASIC LOAD command to load
it.
3. If the code file is so long that it stretches right from the screen
display area to the end of memory, then it will be possible to load
it, but as soon as it has loaded, the machine will crash. This is
because BASIC will have 'lost' its stack.
Exercise...
1. Practise the operations shown in this section until you are
completely au fait with manipulating files to and from the disk, the
RAMdisk, and cassette unit (if connected).