Home » CEEFAX disks » telesoftware5.adl » 12-03-88/SNINFO
12-03-88/SNINFO
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.
| Tape/disk: | Home » CEEFAX disks » telesoftware5.adl |
| Filename: | 12-03-88/SNINFO |
| Read OK: | ✔ |
| File size: | 1F86 bytes |
| Load address: | 0000 |
| Exec address: | 0000 |
File contents
Snapshot Documentation During the 70's Xerox developed Smalltalk - the original WIMP (Windows, Icons, Mice, Pull down/up menus) system, Apple's Lisa and MacIntosh are both developed directly from Smalltalk. During development, the system was prone to crashes, so Snapshot was devised. This would, at set intervals, copy the computer's memory directly onto disc exactly as in the computer. If the system crashed users would then "Boot and Resume", the only problem being that if you did not "Boot and Resume" fast enough then the computer would take a Snapshot of the crashed system. The advantages of being able to Snapshot a computers memory are obvious, especially for machine code programmers or adventurers who forget to save regularly. With Snapshot it is possible to forget about the need to save regularly, and get on with what you are doing. It must be said though that taking a Snapshot of a commercial program can be classed as piracy. If the program is only being moved from tape to disc then the situation is not clear and mainly depends on the software house concerned. Some don't like you moving their software from tape to disc while others don't mind. One problem though is the amount of disc space needed. Even on a BBC with just 32K only 3 Snapshots can be taken on a standard 100K disc so to overcome this each new file is saved over the old one. To implement a Snapshot on a BBC is difficult. Xerox Snapsnots had substantial hardware backup so things were easier. On the BBC there are 3 main problems. First, how to copy all 32K of main RAM to disc without currupting/changing it; second, what if the Operating System work space (that below page) is currupted? This often happens when programmers are short of memory and they use DFS workspace. This means that the DFS will not function correctly. Also where can the program "live" while it is waiting to be run if all memory is used? To overcome these problems I have used Sideways RAM (SWR). The program must be assembled in main RAM and then moved up into SWR. To do this a special program is needed. Also when assembled all the addresses the program uses must be set to point to locations in SWR address range (&8000 - &C000) and not in main RAM (0 - &7FFF) as happens when a program is normally assembled, since most 6502 instructions use absolute address and not relative addressing (which has become more popular on newer proccessors because of it's flexibility). On level 2 BASIC machines this is no problem since "phantom" assembly can be used with O%, where the assembler sets the addresses for one area of memory and places the code in another area. On level 1 BASIC machines this is not available so I have adjusted all the absolute addresses with +&3000 so that phantom assembly is not needed (the code is assembled to &5000, so +&3000 makes all address greater than &8000). Also level 1 machines do not have the EQU assembly function so I have synthesised these functions with the OPT command. The program's operation is quite simple and uses what I call an "Imposter" - a copy of OS workspace before it is corrupted. The imposter is then held in SWR until the Snapshot is taken when it is copied down to it's old position allowing the OS (and DFS) to function as normal - this is particularly important if another filing system has been selected in the meantime. The program uses the 6522 User VIA timer to wait for as long as the user wishes before shooting, so if this unit is disabled or currupted the prorgam will either not shoot at all, or will shoot irregularly - many commercial programs use this device for timing so these cannot be Snapshot. Also model A BBC's were never fitted with this unit so any A that has been not been fully upgraded cannot Snapshot with the timer. The main use of this unit normally is to drive the printer and user port. When the time defined by the user is up the program will copy OS workspace between 0 and &1400 up into SWR then copy the imposter down to the same area so that the disc drive will work normally. Next the rest of RAM (&1401 to &8000) including the screen will be saved to disc, then the old OS work space is copied down into a safe area of RAM (&3000 to &4400) and saved to disc (it not will work with cassette mainly because of the time involved at this stage). Once the memory is saved (including a copy of the stack pointer - A,X and Y are taken care of by OS) the program returns the system to it's previous state. To force the system to return to a previous state the command *RESTORE is issued (see below), this will bring the memory in from disc and carry out the above operation in reverse - if you are only restoring memory from a previous Snapshot and do not intend to take another Snapshot you need not use *READY to get an imposter. The system supports 5 extra *commands. These may be preceded by a P to prevent clashes with other ROMs and in upper or lower case e.g. *PRESTORE and *prestore are the same as *RESTORE. The commands are:- *READY takes a copy of OS workspace into SWR for future use - the imposter. This command must be issued before any Snapshot can be taken. *NOW will attempt to Snapshot once the command is entered. If an imposter is not present with a *READY you will just hear a beep. *WAIT x (where x is a one or two digit hex number between 1 and &FF) will use the 6522 user VIA timer to time delay specified and then Snapshot memory - each extra value causes a wait of about 16 seconds. Again using this without preparing an imposter with *READY will cause a beep. *REPEAT will cause *WAIT x to be re-issued after every Snapshot - causing regular Snapshots. This will stay set until Break is pressed (Break stops all Snapshooting). Don't use *NOW if a repeat has been issued, the results are unpredictable. *RESTORE will restore memory to is previous state. There are a few points about the program which must the noted. When saving memory to disc two file names must the used, Requested when the program is assembled. These should be the filenames you wish to save or load under. The first file name is for the memory above &1400 and the second one for the memory below &1400. You may add a directory and disc number/name to these files as normal. When RESTOREing, the current drive and directory settings are used to recover the Snapshot. Another program must be used to "lift" the main program into SWR. This is the moveup program, which should be assembled to a machine code file on disc before loading Snapshot. It will ask you for the number of the socket the SWR is located in and will create a file call UP on the disc. Once the main program is assembled just type *UP this will load and run the program. Then press BREAK, you should have the message "Snapshot Version PALO004" on typing *HELP. The B+ 128 has SWR in sockets 1,2 13 and 14. Moveup simply switches the SWR into the current paged ROM position and moves all the data into it. Break must be pressed so that the OS can scan the ROM banks and see which contain ROMs (as far as the OS knows the SWR bank with a program in is a ROM). I have not tried Snapshot on an Electron but the minimum requirements for trying are: 16K of SWR, a disc drive and a 6522 User VIA for timer, on the BBC the main job of the User VIA is the drive the printer so Plus 1 should provide one of these. With the B+ the program works as normal, but only main RAM is captured so when shadow modes are in use the screen will not be saved. For some applications this will not be a hindrance. The Master series uses private RAM for a lot of operations and allows PAGE to be set to &E00, the program would therefore need a large amount of alteration. The same principles will apply but more OS workspace will have to be shifted and more than one bank of SWR may be needed. This short program will provide a basic demonstration of Snapshot. 10 *READY 20 *WAIT 1 30 FOR x=0 TO 1400 40 PRINT x 50 NEXT 60 *RESTORE Note that with Snapshot you are not limited to using a BASIC programming environment.
00000000 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000010 20 20 20 53 6e 61 70 73 68 6f 74 20 44 6f 63 75 | Snapshot Docu| 00000020 6d 65 6e 74 61 74 69 6f 6e 0d 0d 44 75 72 69 6e |mentation..Durin| 00000030 67 20 74 68 65 20 37 30 27 73 20 58 65 72 6f 78 |g the 70's Xerox| 00000040 20 64 65 76 65 6c 6f 70 65 64 20 53 6d 61 6c 6c | developed Small| 00000050 74 61 6c 6b 20 2d 20 74 68 65 20 6f 72 69 67 69 |talk - the origi| 00000060 6e 61 6c 20 57 49 4d 50 20 28 57 69 6e 64 6f 77 |nal WIMP (Window| 00000070 73 2c 0d 49 63 6f 6e 73 2c 20 4d 69 63 65 2c 20 |s,.Icons, Mice, | 00000080 50 75 6c 6c 20 64 6f 77 6e 2f 75 70 20 6d 65 6e |Pull down/up men| 00000090 75 73 29 20 73 79 73 74 65 6d 2c 20 41 70 70 6c |us) system, Appl| 000000a0 65 27 73 20 4c 69 73 61 20 61 6e 64 20 4d 61 63 |e's Lisa and Mac| 000000b0 49 6e 74 6f 73 68 20 61 72 65 0d 62 6f 74 68 20 |Intosh are.both | 000000c0 64 65 76 65 6c 6f 70 65 64 20 64 69 72 65 63 74 |developed direct| 000000d0 6c 79 20 66 72 6f 6d 20 53 6d 61 6c 6c 74 61 6c |ly from Smalltal| 000000e0 6b 2e 20 44 75 72 69 6e 67 20 64 65 76 65 6c 6f |k. During develo| 000000f0 70 6d 65 6e 74 2c 20 74 68 65 20 73 79 73 74 65 |pment, the syste| 00000100 6d 0d 77 61 73 20 70 72 6f 6e 65 20 74 6f 20 63 |m.was prone to c| 00000110 72 61 73 68 65 73 2c 20 73 6f 20 53 6e 61 70 73 |rashes, so Snaps| 00000120 68 6f 74 20 77 61 73 20 64 65 76 69 73 65 64 2e |hot was devised.| 00000130 20 54 68 69 73 20 77 6f 75 6c 64 2c 20 61 74 20 | This would, at | 00000140 73 65 74 0d 69 6e 74 65 72 76 61 6c 73 2c 20 63 |set.intervals, c| 00000150 6f 70 79 20 74 68 65 20 63 6f 6d 70 75 74 65 72 |opy the computer| 00000160 27 73 20 6d 65 6d 6f 72 79 20 64 69 72 65 63 74 |'s memory direct| 00000170 6c 79 20 6f 6e 74 6f 20 64 69 73 63 20 65 78 61 |ly onto disc exa| 00000180 63 74 6c 79 20 61 73 20 69 6e 0d 74 68 65 20 63 |ctly as in.the c| 00000190 6f 6d 70 75 74 65 72 2e 20 49 66 20 74 68 65 20 |omputer. If the | 000001a0 73 79 73 74 65 6d 20 63 72 61 73 68 65 64 20 75 |system crashed u| 000001b0 73 65 72 73 20 77 6f 75 6c 64 20 74 68 65 6e 20 |sers would then | 000001c0 22 42 6f 6f 74 20 61 6e 64 20 52 65 73 75 6d 65 |"Boot and Resume| 000001d0 22 2c 0d 74 68 65 20 6f 6e 6c 79 20 70 72 6f 62 |",.the only prob| 000001e0 6c 65 6d 20 62 65 69 6e 67 20 74 68 61 74 20 69 |lem being that i| 000001f0 66 20 79 6f 75 20 64 69 64 20 6e 6f 74 20 22 42 |f you did not "B| 00000200 6f 6f 74 20 61 6e 64 20 52 65 73 75 6d 65 22 20 |oot and Resume" | 00000210 66 61 73 74 20 65 6e 6f 75 67 68 0d 74 68 65 6e |fast enough.then| 00000220 20 74 68 65 20 63 6f 6d 70 75 74 65 72 20 77 6f | the computer wo| 00000230 75 6c 64 20 74 61 6b 65 20 61 20 53 6e 61 70 73 |uld take a Snaps| 00000240 68 6f 74 20 6f 66 20 74 68 65 20 63 72 61 73 68 |hot of the crash| 00000250 65 64 20 73 79 73 74 65 6d 2e 0d 0d 54 68 65 20 |ed system...The | 00000260 61 64 76 61 6e 74 61 67 65 73 20 6f 66 20 62 65 |advantages of be| 00000270 69 6e 67 20 61 62 6c 65 20 74 6f 20 53 6e 61 70 |ing able to Snap| 00000280 73 68 6f 74 20 61 20 63 6f 6d 70 75 74 65 72 73 |shot a computers| 00000290 20 6d 65 6d 6f 72 79 20 61 72 65 20 6f 62 76 69 | memory are obvi| 000002a0 6f 75 73 2c 0d 65 73 70 65 63 69 61 6c 6c 79 20 |ous,.especially | 000002b0 66 6f 72 20 6d 61 63 68 69 6e 65 20 63 6f 64 65 |for machine code| 000002c0 20 70 72 6f 67 72 61 6d 6d 65 72 73 20 6f 72 20 | programmers or | 000002d0 61 64 76 65 6e 74 75 72 65 72 73 20 77 68 6f 20 |adventurers who | 000002e0 66 6f 72 67 65 74 20 74 6f 20 73 61 76 65 0d 72 |forget to save.r| 000002f0 65 67 75 6c 61 72 6c 79 2e 20 57 69 74 68 20 53 |egularly. With S| 00000300 6e 61 70 73 68 6f 74 20 69 74 20 69 73 20 70 6f |napshot it is po| 00000310 73 73 69 62 6c 65 20 74 6f 20 66 6f 72 67 65 74 |ssible to forget| 00000320 20 61 62 6f 75 74 20 74 68 65 20 6e 65 65 64 20 | about the need | 00000330 74 6f 20 73 61 76 65 0d 72 65 67 75 6c 61 72 6c |to save.regularl| 00000340 79 2c 20 61 6e 64 20 67 65 74 20 6f 6e 20 77 69 |y, and get on wi| 00000350 74 68 20 77 68 61 74 20 79 6f 75 20 61 72 65 20 |th what you are | 00000360 64 6f 69 6e 67 2e 20 49 74 20 6d 75 73 74 20 62 |doing. It must b| 00000370 65 20 73 61 69 64 20 74 68 6f 75 67 68 20 74 68 |e said though th| 00000380 61 74 0d 74 61 6b 69 6e 67 20 61 20 53 6e 61 70 |at.taking a Snap| 00000390 73 68 6f 74 20 6f 66 20 61 20 63 6f 6d 6d 65 72 |shot of a commer| 000003a0 63 69 61 6c 20 70 72 6f 67 72 61 6d 20 63 61 6e |cial program can| 000003b0 20 62 65 20 63 6c 61 73 73 65 64 20 61 73 20 70 | be classed as p| 000003c0 69 72 61 63 79 2e 20 49 66 20 74 68 65 0d 70 72 |iracy. If the.pr| 000003d0 6f 67 72 61 6d 20 69 73 20 6f 6e 6c 79 20 62 65 |ogram is only be| 000003e0 69 6e 67 20 6d 6f 76 65 64 20 66 72 6f 6d 20 74 |ing moved from t| 000003f0 61 70 65 20 74 6f 20 64 69 73 63 20 74 68 65 6e |ape to disc then| 00000400 20 74 68 65 20 73 69 74 75 61 74 69 6f 6e 20 69 | the situation i| 00000410 73 20 6e 6f 74 0d 63 6c 65 61 72 20 61 6e 64 20 |s not.clear and | 00000420 6d 61 69 6e 6c 79 20 64 65 70 65 6e 64 73 20 6f |mainly depends o| 00000430 6e 20 74 68 65 20 73 6f 66 74 77 61 72 65 20 68 |n the software h| 00000440 6f 75 73 65 20 63 6f 6e 63 65 72 6e 65 64 2e 20 |ouse concerned. | 00000450 53 6f 6d 65 20 64 6f 6e 27 74 20 6c 69 6b 65 0d |Some don't like.| 00000460 79 6f 75 20 6d 6f 76 69 6e 67 20 74 68 65 69 72 |you moving their| 00000470 20 73 6f 66 74 77 61 72 65 20 66 72 6f 6d 20 74 | software from t| 00000480 61 70 65 20 74 6f 20 64 69 73 63 20 77 68 69 6c |ape to disc whil| 00000490 65 20 6f 74 68 65 72 73 20 64 6f 6e 27 74 20 6d |e others don't m| 000004a0 69 6e 64 2e 0d 0d 4f 6e 65 20 70 72 6f 62 6c 65 |ind...One proble| 000004b0 6d 20 74 68 6f 75 67 68 20 69 73 20 74 68 65 20 |m though is the | 000004c0 61 6d 6f 75 6e 74 20 6f 66 20 64 69 73 63 20 73 |amount of disc s| 000004d0 70 61 63 65 20 6e 65 65 64 65 64 2e 20 45 76 65 |pace needed. Eve| 000004e0 6e 20 6f 6e 20 61 20 42 42 43 20 77 69 74 68 0d |n on a BBC with.| 000004f0 6a 75 73 74 20 33 32 4b 20 6f 6e 6c 79 20 33 20 |just 32K only 3 | 00000500 53 6e 61 70 73 68 6f 74 73 20 63 61 6e 20 62 65 |Snapshots can be| 00000510 20 74 61 6b 65 6e 20 6f 6e 20 61 20 73 74 61 6e | taken on a stan| 00000520 64 61 72 64 20 31 30 30 4b 20 64 69 73 63 20 73 |dard 100K disc s| 00000530 6f 20 74 6f 0d 6f 76 65 72 63 6f 6d 65 20 74 68 |o to.overcome th| 00000540 69 73 20 65 61 63 68 20 6e 65 77 20 66 69 6c 65 |is each new file| 00000550 20 69 73 20 73 61 76 65 64 20 6f 76 65 72 20 74 | is saved over t| 00000560 68 65 20 6f 6c 64 20 6f 6e 65 2e 20 0d 0d 54 6f |he old one. ..To| 00000570 20 69 6d 70 6c 65 6d 65 6e 74 20 61 20 53 6e 61 | implement a Sna| 00000580 70 73 68 6f 74 20 6f 6e 20 61 20 42 42 43 20 69 |pshot on a BBC i| 00000590 73 20 64 69 66 66 69 63 75 6c 74 2e 20 58 65 72 |s difficult. Xer| 000005a0 6f 78 20 53 6e 61 70 73 6e 6f 74 73 20 68 61 64 |ox Snapsnots had| 000005b0 0d 73 75 62 73 74 61 6e 74 69 61 6c 20 68 61 72 |.substantial har| 000005c0 64 77 61 72 65 20 62 61 63 6b 75 70 20 73 6f 20 |dware backup so | 000005d0 74 68 69 6e 67 73 20 77 65 72 65 20 65 61 73 69 |things were easi| 000005e0 65 72 2e 20 4f 6e 20 74 68 65 20 42 42 43 20 74 |er. On the BBC t| 000005f0 68 65 72 65 20 61 72 65 20 33 0d 6d 61 69 6e 20 |here are 3.main | 00000600 70 72 6f 62 6c 65 6d 73 2e 20 46 69 72 73 74 2c |problems. First,| 00000610 20 68 6f 77 20 74 6f 20 63 6f 70 79 20 61 6c 6c | how to copy all| 00000620 20 33 32 4b 20 6f 66 20 6d 61 69 6e 20 52 41 4d | 32K of main RAM| 00000630 20 74 6f 20 64 69 73 63 20 77 69 74 68 6f 75 74 | to disc without| 00000640 0d 63 75 72 72 75 70 74 69 6e 67 2f 63 68 61 6e |.currupting/chan| 00000650 67 69 6e 67 20 69 74 3b 20 73 65 63 6f 6e 64 2c |ging it; second,| 00000660 20 77 68 61 74 20 69 66 20 74 68 65 20 4f 70 65 | what if the Ope| 00000670 72 61 74 69 6e 67 20 53 79 73 74 65 6d 20 77 6f |rating System wo| 00000680 72 6b 20 73 70 61 63 65 0d 28 74 68 61 74 20 62 |rk space.(that b| 00000690 65 6c 6f 77 20 70 61 67 65 29 20 69 73 20 63 75 |elow page) is cu| 000006a0 72 72 75 70 74 65 64 3f 20 54 68 69 73 20 6f 66 |rrupted? This of| 000006b0 74 65 6e 20 68 61 70 70 65 6e 73 20 77 68 65 6e |ten happens when| 000006c0 20 70 72 6f 67 72 61 6d 6d 65 72 73 20 61 72 65 | programmers are| 000006d0 0d 73 68 6f 72 74 20 6f 66 20 6d 65 6d 6f 72 79 |.short of memory| 000006e0 20 61 6e 64 20 74 68 65 79 20 75 73 65 20 44 46 | and they use DF| 000006f0 53 20 77 6f 72 6b 73 70 61 63 65 2e 20 54 68 69 |S workspace. Thi| 00000700 73 20 6d 65 61 6e 73 20 74 68 61 74 20 74 68 65 |s means that the| 00000710 20 44 46 53 20 77 69 6c 6c 0d 6e 6f 74 20 66 75 | DFS will.not fu| 00000720 6e 63 74 69 6f 6e 20 63 6f 72 72 65 63 74 6c 79 |nction correctly| 00000730 2e 20 41 6c 73 6f 20 77 68 65 72 65 20 63 61 6e |. Also where can| 00000740 20 74 68 65 20 70 72 6f 67 72 61 6d 20 22 6c 69 | the program "li| 00000750 76 65 22 20 77 68 69 6c 65 20 69 74 20 69 73 0d |ve" while it is.| 00000760 77 61 69 74 69 6e 67 20 74 6f 20 62 65 20 72 75 |waiting to be ru| 00000770 6e 20 69 66 20 61 6c 6c 20 6d 65 6d 6f 72 79 20 |n if all memory | 00000780 69 73 20 75 73 65 64 3f 0d 0d 54 6f 20 6f 76 65 |is used?..To ove| 00000790 72 63 6f 6d 65 20 74 68 65 73 65 20 70 72 6f 62 |rcome these prob| 000007a0 6c 65 6d 73 20 49 20 68 61 76 65 20 75 73 65 64 |lems I have used| 000007b0 20 53 69 64 65 77 61 79 73 20 52 41 4d 20 28 53 | Sideways RAM (S| 000007c0 57 52 29 2e 20 54 68 65 20 70 72 6f 67 72 61 6d |WR). The program| 000007d0 0d 6d 75 73 74 20 62 65 20 61 73 73 65 6d 62 6c |.must be assembl| 000007e0 65 64 20 69 6e 20 6d 61 69 6e 20 52 41 4d 20 61 |ed in main RAM a| 000007f0 6e 64 20 74 68 65 6e 20 6d 6f 76 65 64 20 75 70 |nd then moved up| 00000800 20 69 6e 74 6f 20 53 57 52 2e 20 54 6f 20 64 6f | into SWR. To do| 00000810 20 74 68 69 73 20 61 0d 73 70 65 63 69 61 6c 20 | this a.special | 00000820 70 72 6f 67 72 61 6d 20 69 73 20 6e 65 65 64 65 |program is neede| 00000830 64 2e 20 41 6c 73 6f 20 77 68 65 6e 20 61 73 73 |d. Also when ass| 00000840 65 6d 62 6c 65 64 20 61 6c 6c 20 74 68 65 20 61 |embled all the a| 00000850 64 64 72 65 73 73 65 73 20 74 68 65 0d 70 72 6f |ddresses the.pro| 00000860 67 72 61 6d 20 75 73 65 73 20 6d 75 73 74 20 62 |gram uses must b| 00000870 65 20 73 65 74 20 74 6f 20 70 6f 69 6e 74 20 74 |e set to point t| 00000880 6f 20 6c 6f 63 61 74 69 6f 6e 73 20 69 6e 20 53 |o locations in S| 00000890 57 52 20 61 64 64 72 65 73 73 20 72 61 6e 67 65 |WR address range| 000008a0 20 28 26 38 30 30 30 0d 2d 20 26 43 30 30 30 29 | (&8000.- &C000)| 000008b0 20 61 6e 64 20 6e 6f 74 20 69 6e 20 6d 61 69 6e | and not in main| 000008c0 20 52 41 4d 20 28 30 20 2d 20 26 37 46 46 46 29 | RAM (0 - &7FFF)| 000008d0 20 61 73 20 68 61 70 70 65 6e 73 20 77 68 65 6e | as happens when| 000008e0 20 61 20 70 72 6f 67 72 61 6d 20 69 73 0d 6e 6f | a program is.no| 000008f0 72 6d 61 6c 6c 79 20 61 73 73 65 6d 62 6c 65 64 |rmally assembled| 00000900 2c 20 73 69 6e 63 65 20 6d 6f 73 74 20 36 35 30 |, since most 650| 00000910 32 20 69 6e 73 74 72 75 63 74 69 6f 6e 73 20 75 |2 instructions u| 00000920 73 65 20 61 62 73 6f 6c 75 74 65 20 61 64 64 72 |se absolute addr| 00000930 65 73 73 20 61 6e 64 0d 6e 6f 74 20 72 65 6c 61 |ess and.not rela| 00000940 74 69 76 65 20 61 64 64 72 65 73 73 69 6e 67 20 |tive addressing | 00000950 28 77 68 69 63 68 20 68 61 73 20 62 65 63 6f 6d |(which has becom| 00000960 65 20 6d 6f 72 65 20 70 6f 70 75 6c 61 72 20 6f |e more popular o| 00000970 6e 20 6e 65 77 65 72 0d 70 72 6f 63 63 65 73 73 |n newer.proccess| 00000980 6f 72 73 20 62 65 63 61 75 73 65 20 6f 66 20 69 |ors because of i| 00000990 74 27 73 20 66 6c 65 78 69 62 69 6c 69 74 79 29 |t's flexibility)| 000009a0 2e 20 4f 6e 20 6c 65 76 65 6c 20 32 20 42 41 53 |. On level 2 BAS| 000009b0 49 43 20 6d 61 63 68 69 6e 65 73 20 74 68 69 73 |IC machines this| 000009c0 0d 69 73 20 6e 6f 20 70 72 6f 62 6c 65 6d 20 73 |.is no problem s| 000009d0 69 6e 63 65 20 22 70 68 61 6e 74 6f 6d 22 20 61 |ince "phantom" a| 000009e0 73 73 65 6d 62 6c 79 20 63 61 6e 20 62 65 20 75 |ssembly can be u| 000009f0 73 65 64 20 77 69 74 68 20 4f 25 2c 20 77 68 65 |sed with O%, whe| 00000a00 72 65 20 74 68 65 0d 61 73 73 65 6d 62 6c 65 72 |re the.assembler| 00000a10 20 73 65 74 73 20 74 68 65 20 61 64 64 72 65 73 | sets the addres| 00000a20 73 65 73 20 66 6f 72 20 6f 6e 65 20 61 72 65 61 |ses for one area| 00000a30 20 6f 66 20 6d 65 6d 6f 72 79 20 61 6e 64 20 70 | of memory and p| 00000a40 6c 61 63 65 73 20 74 68 65 20 63 6f 64 65 20 69 |laces the code i| 00000a50 6e 0d 61 6e 6f 74 68 65 72 20 61 72 65 61 2e 20 |n.another area. | 00000a60 4f 6e 20 6c 65 76 65 6c 20 31 20 42 41 53 49 43 |On level 1 BASIC| 00000a70 20 6d 61 63 68 69 6e 65 73 20 74 68 69 73 20 69 | machines this i| 00000a80 73 20 6e 6f 74 20 61 76 61 69 6c 61 62 6c 65 20 |s not available | 00000a90 73 6f 20 49 20 68 61 76 65 0d 61 64 6a 75 73 74 |so I have.adjust| 00000aa0 65 64 20 61 6c 6c 20 74 68 65 20 61 62 73 6f 6c |ed all the absol| 00000ab0 75 74 65 20 61 64 64 72 65 73 73 65 73 20 77 69 |ute addresses wi| 00000ac0 74 68 20 2b 26 33 30 30 30 20 73 6f 20 74 68 61 |th +&3000 so tha| 00000ad0 74 20 70 68 61 6e 74 6f 6d 20 61 73 73 65 6d 62 |t phantom assemb| 00000ae0 6c 79 0d 69 73 20 6e 6f 74 20 6e 65 65 64 65 64 |ly.is not needed| 00000af0 20 28 74 68 65 20 63 6f 64 65 20 69 73 20 61 73 | (the code is as| 00000b00 73 65 6d 62 6c 65 64 20 74 6f 20 26 35 30 30 30 |sembled to &5000| 00000b10 2c 20 73 6f 20 2b 26 33 30 30 30 20 6d 61 6b 65 |, so +&3000 make| 00000b20 73 20 61 6c 6c 20 61 64 64 72 65 73 73 0d 67 72 |s all address.gr| 00000b30 65 61 74 65 72 20 74 68 61 6e 20 26 38 30 30 30 |eater than &8000| 00000b40 29 2e 20 41 6c 73 6f 20 6c 65 76 65 6c 20 31 20 |). Also level 1 | 00000b50 6d 61 63 68 69 6e 65 73 20 64 6f 20 6e 6f 74 20 |machines do not | 00000b60 68 61 76 65 20 74 68 65 20 45 51 55 20 61 73 73 |have the EQU ass| 00000b70 65 6d 62 6c 79 0d 66 75 6e 63 74 69 6f 6e 20 73 |embly.function s| 00000b80 6f 20 49 20 68 61 76 65 20 73 79 6e 74 68 65 73 |o I have synthes| 00000b90 69 73 65 64 20 74 68 65 73 65 20 66 75 6e 63 74 |ised these funct| 00000ba0 69 6f 6e 73 20 77 69 74 68 20 74 68 65 20 4f 50 |ions with the OP| 00000bb0 54 20 63 6f 6d 6d 61 6e 64 2e 0d 0d 54 68 65 20 |T command...The | 00000bc0 70 72 6f 67 72 61 6d 27 73 20 6f 70 65 72 61 74 |program's operat| 00000bd0 69 6f 6e 20 69 73 20 71 75 69 74 65 20 73 69 6d |ion is quite sim| 00000be0 70 6c 65 20 61 6e 64 20 75 73 65 73 20 77 68 61 |ple and uses wha| 00000bf0 74 20 49 20 63 61 6c 6c 20 61 6e 20 22 49 6d 70 |t I call an "Imp| 00000c00 6f 73 74 65 72 22 0d 2d 20 61 20 63 6f 70 79 20 |oster".- a copy | 00000c10 6f 66 20 4f 53 20 77 6f 72 6b 73 70 61 63 65 20 |of OS workspace | 00000c20 62 65 66 6f 72 65 20 69 74 20 69 73 20 63 6f 72 |before it is cor| 00000c30 72 75 70 74 65 64 2e 20 54 68 65 20 69 6d 70 6f |rupted. 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It will a| 00001990 73 6b 20 79 6f 75 20 66 6f 72 20 74 68 65 20 6e |sk you for the n| 000019a0 75 6d 62 65 72 20 6f 66 20 74 68 65 20 73 6f 63 |umber of the soc| 000019b0 6b 65 74 0d 74 68 65 20 53 57 52 20 69 73 20 6c |ket.the SWR is l| 000019c0 6f 63 61 74 65 64 20 69 6e 20 61 6e 64 20 77 69 |ocated in and wi| 000019d0 6c 6c 20 63 72 65 61 74 65 20 61 20 66 69 6c 65 |ll create a file| 000019e0 20 63 61 6c 6c 20 55 50 20 6f 6e 20 74 68 65 20 | call UP on the | 000019f0 64 69 73 63 2e 20 4f 6e 63 65 20 74 68 65 0d 6d |disc. Once the.m| 00001a00 61 69 6e 20 70 72 6f 67 72 61 6d 20 69 73 20 61 |ain program is a| 00001a10 73 73 65 6d 62 6c 65 64 20 6a 75 73 74 20 74 79 |ssembled just ty| 00001a20 70 65 20 2a 55 50 20 74 68 69 73 20 77 69 6c 6c |pe *UP this will| 00001a30 20 6c 6f 61 64 20 61 6e 64 20 72 75 6e 20 74 68 | load and run th| 00001a40 65 0d 70 72 6f 67 72 61 6d 2e 20 54 68 65 6e 20 |e.program. Then | 00001a50 70 72 65 73 73 20 42 52 45 41 4b 2c 20 79 6f 75 |press BREAK, you| 00001a60 20 73 68 6f 75 6c 64 20 68 61 76 65 20 74 68 65 | should have the| 00001a70 20 6d 65 73 73 61 67 65 20 22 53 6e 61 70 73 68 | message "Snapsh| 00001a80 6f 74 20 56 65 72 73 69 6f 6e 0d 50 41 4c 4f 30 |ot Version.PALO0| 00001a90 30 34 22 20 6f 6e 20 74 79 70 69 6e 67 20 2a 48 |04" on typing *H| 00001aa0 45 4c 50 2e 20 54 68 65 20 42 2b 20 31 32 38 20 |ELP. The B+ 128 | 00001ab0 68 61 73 20 53 57 52 20 69 6e 20 73 6f 63 6b 65 |has SWR in socke| 00001ac0 74 73 20 31 2c 32 20 31 33 20 61 6e 64 20 31 34 |ts 1,2 13 and 14| 00001ad0 2e 0d 4d 6f 76 65 75 70 20 73 69 6d 70 6c 79 20 |..Moveup simply | 00001ae0 73 77 69 74 63 68 65 73 20 74 68 65 20 53 57 52 |switches the SWR| 00001af0 20 69 6e 74 6f 20 74 68 65 20 63 75 72 72 65 6e | into the curren| 00001b00 74 20 70 61 67 65 64 20 52 4f 4d 20 70 6f 73 69 |t paged ROM posi| 00001b10 74 69 6f 6e 20 61 6e 64 0d 6d 6f 76 65 73 20 61 |tion and.moves a| 00001b20 6c 6c 20 74 68 65 20 64 61 74 61 20 69 6e 74 6f |ll the data into| 00001b30 20 69 74 2e 20 42 72 65 61 6b 20 6d 75 73 74 20 | it. Break must | 00001b40 62 65 20 70 72 65 73 73 65 64 20 73 6f 20 74 68 |be pressed so th| 00001b50 61 74 20 74 68 65 20 4f 53 20 63 61 6e 20 73 63 |at the OS can sc| 00001b60 61 6e 0d 74 68 65 20 52 4f 4d 20 62 61 6e 6b 73 |an.the ROM banks| 00001b70 20 61 6e 64 20 73 65 65 20 77 68 69 63 68 20 63 | and see which c| 00001b80 6f 6e 74 61 69 6e 20 52 4f 4d 73 20 28 61 73 20 |ontain ROMs (as | 00001b90 66 61 72 20 61 73 20 74 68 65 20 4f 53 20 6b 6e |far as the OS kn| 00001ba0 6f 77 73 20 74 68 65 20 53 57 52 0d 62 61 6e 6b |ows the SWR.bank| 00001bb0 20 77 69 74 68 20 61 20 70 72 6f 67 72 61 6d 20 | with a program | 00001bc0 69 6e 20 69 73 20 61 20 52 4f 4d 29 2e 0d 0d 49 |in is a ROM)...I| 00001bd0 20 68 61 76 65 20 6e 6f 74 20 74 72 69 65 64 20 | have not tried | 00001be0 53 6e 61 70 73 68 6f 74 20 6f 6e 20 61 6e 20 45 |Snapshot on an E| 00001bf0 6c 65 63 74 72 6f 6e 20 62 75 74 20 74 68 65 20 |lectron but the | 00001c00 6d 69 6e 69 6d 75 6d 20 72 65 71 75 69 72 65 6d |minimum requirem| 00001c10 65 6e 74 73 20 66 6f 72 0d 74 72 79 69 6e 67 20 |ents for.trying | 00001c20 61 72 65 3a 20 31 36 4b 20 6f 66 20 53 57 52 2c |are: 16K of SWR,| 00001c30 20 61 20 64 69 73 63 20 64 72 69 76 65 20 61 6e | a disc drive an| 00001c40 64 20 61 20 36 35 32 32 20 55 73 65 72 20 56 49 |d a 6522 User VI| 00001c50 41 20 66 6f 72 20 74 69 6d 65 72 2c 20 6f 6e 20 |A for timer, on | 00001c60 74 68 65 0d 42 42 43 20 74 68 65 20 6d 61 69 6e |the.BBC the main| 00001c70 20 6a 6f 62 20 6f 66 20 74 68 65 20 55 73 65 72 | job of the User| 00001c80 20 56 49 41 20 69 73 20 74 68 65 20 64 72 69 76 | VIA is the driv| 00001c90 65 20 74 68 65 20 70 72 69 6e 74 65 72 20 73 6f |e the printer so| 00001ca0 20 50 6c 75 73 20 31 20 73 68 6f 75 6c 64 0d 70 | Plus 1 should.p| 00001cb0 72 6f 76 69 64 65 20 6f 6e 65 20 6f 66 20 74 68 |rovide one of th| 00001cc0 65 73 65 2e 20 57 69 74 68 20 74 68 65 20 42 2b |ese. With the B+| 00001cd0 20 74 68 65 20 70 72 6f 67 72 61 6d 20 77 6f 72 | the program wor| 00001ce0 6b 73 20 61 73 20 6e 6f 72 6d 61 6c 2c 20 62 75 |ks as normal, bu| 00001cf0 74 20 6f 6e 6c 79 0d 6d 61 69 6e 20 52 41 4d 20 |t only.main RAM | 00001d00 69 73 20 63 61 70 74 75 72 65 64 20 73 6f 20 77 |is captured so w| 00001d10 68 65 6e 20 73 68 61 64 6f 77 20 6d 6f 64 65 73 |hen shadow modes| 00001d20 20 61 72 65 20 69 6e 20 75 73 65 20 74 68 65 20 | are in use the | 00001d30 73 63 72 65 65 6e 20 77 69 6c 6c 20 6e 6f 74 0d |screen will not.| 00001d40 62 65 20 73 61 76 65 64 2e 20 46 6f 72 20 73 6f |be saved. For so| 00001d50 6d 65 20 61 70 70 6c 69 63 61 74 69 6f 6e 73 20 |me applications | 00001d60 74 68 69 73 20 77 69 6c 6c 20 6e 6f 74 20 62 65 |this will not be| 00001d70 20 61 20 68 69 6e 64 72 61 6e 63 65 2e 0d 0d 54 | a hindrance...T| 00001d80 68 65 20 4d 61 73 74 65 72 20 73 65 72 69 65 73 |he Master series| 00001d90 20 75 73 65 73 20 70 72 69 76 61 74 65 20 52 41 | uses private RA| 00001da0 4d 20 66 6f 72 20 61 20 6c 6f 74 20 6f 66 20 6f |M for a lot of o| 00001db0 70 65 72 61 74 69 6f 6e 73 20 61 6e 64 20 61 6c |perations and al| 00001dc0 6c 6f 77 73 20 50 41 47 45 0d 74 6f 20 62 65 20 |lows PAGE.to be | 00001dd0 73 65 74 20 74 6f 20 26 45 30 30 2c 20 74 68 65 |set to &E00, the| 00001de0 20 70 72 6f 67 72 61 6d 20 77 6f 75 6c 64 20 74 | program would t| 00001df0 68 65 72 65 66 6f 72 65 20 6e 65 65 64 20 61 20 |herefore need a | 00001e00 6c 61 72 67 65 20 61 6d 6f 75 6e 74 20 6f 66 0d |large amount of.| 00001e10 61 6c 74 65 72 61 74 69 6f 6e 2e 20 54 68 65 20 |alteration. The | 00001e20 73 61 6d 65 20 70 72 69 6e 63 69 70 6c 65 73 20 |same principles | 00001e30 77 69 6c 6c 20 61 70 70 6c 79 20 62 75 74 20 6d |will apply but m| 00001e40 6f 72 65 20 4f 53 20 77 6f 72 6b 73 70 61 63 65 |ore OS workspace| 00001e50 20 77 69 6c 6c 20 68 61 76 65 0d 74 6f 20 62 65 | will have.to be| 00001e60 20 73 68 69 66 74 65 64 20 61 6e 64 20 6d 6f 72 | shifted and mor| 00001e70 65 20 74 68 61 6e 20 6f 6e 65 20 62 61 6e 6b 20 |e than one bank | 00001e80 6f 66 20 53 57 52 20 6d 61 79 20 62 65 20 6e 65 |of SWR may be ne| 00001e90 65 64 65 64 2e 0d 0d 54 68 69 73 20 73 68 6f 72 |eded...This shor| 00001ea0 74 20 70 72 6f 67 72 61 6d 20 77 69 6c 6c 20 70 |t program will p| 00001eb0 72 6f 76 69 64 65 20 61 20 62 61 73 69 63 20 64 |rovide a basic d| 00001ec0 65 6d 6f 6e 73 74 72 61 74 69 6f 6e 20 6f 66 20 |emonstration of | 00001ed0 53 6e 61 70 73 68 6f 74 2e 0d 09 09 31 30 20 2a |Snapshot....10 *| 00001ee0 52 45 41 44 59 0d 09 09 32 30 20 2a 57 41 49 54 |READY...20 *WAIT| 00001ef0 20 31 0d 09 09 33 30 20 46 4f 52 20 78 3d 30 20 | 1...30 FOR x=0 | 00001f00 54 4f 20 31 34 30 30 0d 09 09 34 30 20 50 52 49 |TO 1400...40 PRI| 00001f10 4e 54 20 78 0d 09 09 35 30 20 4e 45 58 54 0d 09 |NT x...50 NEXT..| 00001f20 09 36 30 20 2a 52 45 53 54 4f 52 45 0d 20 09 0d |.60 *RESTORE. ..| 00001f30 4e 6f 74 65 20 74 68 61 74 20 77 69 74 68 20 53 |Note that with S| 00001f40 6e 61 70 73 68 6f 74 20 79 6f 75 20 61 72 65 20 |napshot you are | 00001f50 6e 6f 74 20 6c 69 6d 69 74 65 64 20 74 6f 20 75 |not limited to u| 00001f60 73 69 6e 67 20 61 20 42 41 53 49 43 20 70 72 6f |sing a BASIC pro| 00001f70 67 72 61 6d 6d 69 6e 67 0d 65 6e 76 69 72 6f 6e |gramming.environ| 00001f80 6d 65 6e 74 2e 0d |ment..| 00001f86
12-03-88/SNINFO.m0
12-03-88/SNINFO.m1
12-03-88/SNINFO.m2
12-03-88/SNINFO.m4
12-03-88/SNINFO.m5
.