The canonical list of +3 oddities (first posted on comp.sys.sinclar on 15th March 1994) Note: This list applies to ROM version 4.0. The version number may be seen from the system test message (see 1(b) below). I'm told that most +3 machines have version 4.0 while most +2A machines have version 4.1. I have never examined this updated ROM and would be interested to know how many of the following things apply to it also. 1. Strange Features (a) In ROM1 - At 2AA8 is the message "You should never see this". It is right, because error messages are generated from a message address table, and the address of this message isn't in that table. - At 2AC1 is the message "Hello there!" - At 3283 is the name of the temporary file used by COPY: "M:VAXNSUZ.$$$". Don't save a file of this name and expect it to stay there while you copy a file from disk to disk! - At 35C4 is the COPY RANDOMIZE routine. Between the time you press enter after typing this command and the appearance of the red error cursor, you have about a quarter of a second in which to press simultaneously the keys C, J and L. Don't use this command when you have valuable data in memory! (b) In ROM0 - From the test screen, press keys Q, A, Z, P, L and M together. This brings up the system test (which starts at 21DF and occupies most of the rest of the ROM). - From the test screen, press keys E, U and A together and then play a tape (this routine is at 22D0-22FD). - The test screen can be ended by pressing B and V together. The machine resets. - The editor has a bunch of editing keys (table at 05E6): TAB up 10 AT down 10 CODE left word VAL$ right word INKEY$ top RND bottom FN start of line PI end of line SCREEN$ delete char right COS delete word right TAN delete word left VAL delete line right LEN delete line left POINT screen (same as "Screen" in +3 basic menu) 2. Strange Feechurs (aka buglets) (a) In ROM1 046D: The erase message goes to a recently-used stream, not always to the lower screen. For example, PRINT : ERASE "*.bak" prints the "Erase *.bak?" message on the main screen. Also, the lower screen is cleared only if you press Y. If you press N then the message stays there even if it was printed in the right place. 0769: "SUB +40" should be "SUB +3F". The effect of this is that the CAT command will only give up to 63 file names, even if there are more files on the disk. 083E: The jump is made to an incorrect location if the load-bytes routine is called to verify. This is mostly harmless, because the BASIC VERIFY command doesn't attempt to verify at all. 0998: A file name such as "T:file" is correctly diverted to tape, but does not have its leading "T:" stripped off. 1236: CLEAR may leave the GOSUB stack without an end marker if it was non-empty before the CLEAR [example 1]. 1883: A volume instruction in a PLAY command attempts to output the volume to the sound chip even for channels 4 to 8 [example 2]. It should not output the volume at all, since that will be done at 1C74. Not only is it one time-unit early to output the volume [example 3], but it also means that PLAY "V10&" and PLAY "&","V10" both make spurious sounds. 189B: The U instruction in a PLAY command sets the stored volume number to 1F even for channels 4 to 8. The programmer appears to have intended to output this value to the sound chip, but forgotten. This is a bonus (see above). Note that notes sent to a MIDI channel will be of volume 15 after a U instruction, even on channels 4 to 8. 1BFA: A key-up signal is sent to the MIDI port even after a rest. This signal will be for the most recently played note in the current string. For instance, PLAY "Y1a&","Y1N9a" will sound only for a minim. 1F08: The delay to wait for stop bits after an input is (BAUD)-7. This value is not checked for overflow, so this delay effectively prevents communication at 19200 baud, which would otherwise be OK. 2017: TVPARS is set to accept two parameters after a colour control code, rather than just 1. This means that the A in LPRINT INK 3;"A" is absorbed. This routine also exits with carry and zero reset unless the character was an INK control (see 2B60 and example 4). 2020: Any control byte is stored in TVDATA, which might change in certain unusual circumstances [example 5]. 202B: When all the bytes of a colour control routine have been received, this routine returns with carry and zero both reset (see 2B60 and example 4). 219C: A "LD (TVFLAG),1" should probably be "LD (DFSZ),1" (harmless). 21FA: COPY capitalises the drive letter in each file name. This has a permanent effect if the file name was written in the BASIC program or in a variable. 25D6: The error reporting routine contains HALT, as does the normal spectrum one. 2624: If the error number in 23610 is out of range, the error reporting routine crashes because it does not check the range before using it as an index to a message address table. 2B09: There is a special case for RS232 input which occurs when the 48K BASIC editor is active, for example in INPUT #3;a. It traps both input and output, but does not check before entering an input loop (this is probably OK since the editor does not print anything before this loop gets control). However, before making a return it calculates the wrong value to be output to port 1FFD, namely (BANKM)|#10. This will cause a crash. 2B60: The routine which is called for both input and output on channel "P" checks the flags before returning. If both carry and zero are reset, then it reports "End of file". This should only happen on input (see 2017 and 202B). 2DF3: The copy-disk-to-disk routine appears to check both source and destination to see that they are not "M:" (if they are then they will be treated as normal files and hence give a bad filename error). However the test is done in upper case on a lower case letter and so always fails. The routine opens source and destination drives and then, assuming that "M:" is not involved, it tries to open the temporary file unless the RAM drive is too full. This gives "File already in use" - but apparently not before the contents of the destination drive have been erased. In any case, copying between "M:" and "A:" should not be allowed because they have different formats. 2ECD: A buffer starting at ED11 and of length 0800 is used by the COPY command. This is almost certainly supposed to be in page 7, but instead it is in page 0 where it will overwrite an area of user memory. If RAMTOP (and hence the machine stack) is in that area when the COPY command is executed then the machine will crash. This error also occurs at 2F12, 2F61, 2FA7, 3024 and 3043. 3150: The length of the string ".HED#" (where # is an end marker, code FF) as used in COPY TO SPECTRUM FORMAT is given as 4. This may result in "Bad filename" unless the original file had a file extension of the same length (in which case the original name's end marker is in the right place for the new name). (b) In ROM2 016C: BANK678 is not initialised. It should be set equal to #10 so that the STROBE of the centronics port is set high. Some printers cope with an inverted STROBE, but some don't. 079E: The key beep routine (which is also used for the longer beep when a key press is not accepted) uses 0C80 for the frequency, whereas the 48K spectrum uses 00C8. This means that the value stored in PIP has 16 times as much effect on the note duration in editor mode as it does during the command INPUT. 0A27: The "line has altered" flag is not cleared when a null line is entered (for example, if you type a space then delete it and press enter). This means that if you move the cursor up or down on to a program line then the program line is considered to have been changed. 0E13: The "alternate cursor column" is corrupted after a syntax error. If the cursor was moved from its original position into its error position then the alternate column is zero and the next up or down movement will cause the cursor to jump to the left-hand side of the screen. If it stayed in the same place then the alternate column is random and so moving up or down will cause unpredictable results [example 6]. 0E6F: "LD HL,(F9DB)" should be "LD HL,F9DB". This causes several undesirable effects with lines that go off the top of the screen (this is only a problem when using the lower-screen editing mode). One possible effect is that one or more complete lines are deleted from your input when you press enter. Another is that there is a delay before the line is successfully entered and when the line is displayed there is a beep and a red cursor on the line. 10E4: After del-word-left and del-word-right, an incorrect "alternate cursor column" is stored. 142C: "RET NC" should be "RET" (harmless). 14AF: On the 48K spectrum, leading spaces are only printed for token codes >=197 starting with a letter. On the +3, all tokens have spaces before and after. 153D: A program which has a line 0 will display that line ad infinitum if the stored current line number is zero. This leads to an infinite loop if you try to add a program line. 156E: A line number of 0 is displayed as all blanks. 1A95: When calculating the highest theoretical line number for "renumber", the program ignores the carry flag. If the line increment is unusually large this might result in an erroneous renumber being accepted and carried out. The result of doing this will probably crash the machine (in the routine at 1C12) if it is renumbered again. 1B48: If a GOTO cannot be renumbered, the routine just returns instead of warning the user (similarly at 1B63). 1B6C: When the renumber routine fetches the number from after a GOTO, it ignores the flags from the "get integer" routine. Thus, if the number is over 65535 then the routine will fetch a (seemingly) random value. If this value, or indeed any number following GOTO, is too large (for example, try GOTO 65535) then the program will crash in routine 196E, LINE-ADDR in the spectrum ROM because this routine does not cope with too-big line numbers. 1B73: The programmer intends a GOTO which points past the end of the program to be renumbered to 9999. If the program has no variables, this will happen. Otherwise, such a line will be numbered to the lowest line number not used by the program. This is due to the test "CP #80:JR NZ,notend" to test for the end of the program, which should be either "AND #C0: JR Z,notend" or "CP #28:JR C,notend". 1F71: "CALL 202F" should be "CALL 1FA9". If the character ">" or "<" is followed (without a space) by a sequence of letters and then anything except "$", "#" or a space and some more letters, then the character and the sequence of letters is exchanged when you press enter. For example, "IF foo1