- its line number is in decimal digits, and it should be in the hi-lo form in which it is kept in the program area; the line number is in BC anyway - it needs its length bytes to be inserted after the linenumber): - put the current line number in 5C4A E PPC - get a pointer to the start of the line from 5C5D CH ADD; it was put there, after the line number, by the call to 19FB E LINE NO in MAIN 3 - put the address 1555 REPORT G "No room for line" on the stack; the stack is empty, so this is temporarily the error address. Unlike all the other REPORT routines it makes no call to 0008 ERROR 1 and just jumps to MAIN G; the only possible error is in the call to MAKE ROOM in MAIN ADD1 - subtract the line start address from the end of the editing area stored in 5C61 WORKSP, less one; this is the line length, excluding its line number and length bytes but includingthe newline at the end - call 196E LINE ADDR to check if there is a line in theprogram with the same number - if not jump on to MAIN ADD1 - call 1988 NEXT ONE and 19E8 RECLAIM 2; this deletes the old line from the program. _157D_MAIN_ADD1: if the line length is one, just the newline, jump on to MAIN ADD2; deleting the old line is all thatis required. [A BASIC line consisting of a space only, or colourcontrols only, is copied to the BASIC program: such lines can beused to punctuate or colour code BASIC programs] - increase the length by four for the line number and length bytes - move the BASIC pointer returned by LINE ADDR back to the byte before the insertion - save the pointer from 5C53 PROG - call 1655 MAKE ROOM to make a space in the program at the pointer - restore PROG from the stack; if the line inserted was the first line, 1664 POINTERS called by MAKE ROOM has moved PROGup - get the line length of the line in the editing area, without its line number - copy the BASIC to the program area, from the end backwards; the end is two before the address in 5C61 WORKSP, ie omitting the newline - get the line number from 5C49 E PPC - copy the length bytes in lo-hi order and the line number in hi-lo order backwards into the remaining four bytes. _15AB_MAIN_ADD2: drop the REPORT G error address and jumpback to MAIN EXEC. BASIC line, BASIC line number, BASIC statement see also 5C49E PPC, 1695 LINE NO, 24FB SCANNING, 5C6C S TOP, 5C3C TV FLAG/4 Lines are input to the lower screen, or brought down from the program for revision there, by the 0F2C EDITOR subroutine. The new line or the line being revised is first copied or input to the editing area, and printed from there to the lower screen. When ENTER is hit, the line is checked for syntax by 1B17 LINE SCAN; if it isn't correct, execution returnsimmediately to EDITOR and the line is displayed again with an error cursor. When it has passed syntax, if it has a line numberit is transferred into the program area by 155D MAIN ADD; see BASIC execution above. The format of the_BASIC_line_in_the_program_area is: 1st two bytes:_line_number, as a two-byte integer but reversed; hi byte followed by low byte, converted to this form by 157D MAIN ADD1 3rd and 4th bytes:_length, including the final newline but excluding the line number and length bytes followed by the bytes of the line: any number in decimal,binary or E-format is followed by the number marker 0Eh/14d and then by five bytes giving the FP format of the number concluded by 0Dh/13d newline. Variable letters in the BASIC line in the program area may be upper or lower case, and don't have the type flags in their first three bits, and numeric variables or expressions other than simple numbers aren't followed by the FP form. The format of the line in the editing area differs as follows: the line number is an ordinary BASIC decimal the length bytes are omitted the number markers and FP forms are omitted. _Statement_numbers aren't recorded anywhere, but counted up as required in a_statement_counter by counting colon characters from the end of the line. System variables holding line numbers: E PPC, NEWPPC, NXTLIN, OLDPPC, PPC, S TOP; holding statement numbers: NSPPC, OSPCC, SUBPPC; holding pointers to the BASIC program: CH ADD, DATADD, DEFADD, KCUR, PROG, X PTR. _Terminators, marking the end of statements or lines, are the newline 0Dh marking the end of the line the colon marking the end of a statement THEN is also taken as a statement terminator for most purposes, but not in counting statement numbers. Another form of BASIC line is the "expression", string or numeric, typed in by the user in response to an INPUT command: it cannot have a line number or contain BASIC commands it is input not to the editing area but to the work space, where it is evaluated by SCANNING and its value given to a variable; but as before, it is copied as it is input from the work space to the lower screen. The EDITOR subroutine is used to produce the input just as in typing in BASIC commands. Introduction considered by BASIC INTERPRETER 0020 NEXT CHAR steps along as line interpreted 007D SKIP OVER return if end reached 0692 SA DATA 1 checks end of SAVE etc array statement 06C3 SA CODE check for end of statement 0723 SA LINE 1 finds LINE line number 0873 LD PROG check start line saved with program 08B6 ME CONTRL part ii merges lines into old program 08D2 ME NEW LP checks number of new line 08D7 ME OLD LP compares number of old line 08DF ME OLD L1 finds place for new line 08EB ME NEW L2 enter new line 092C ME ENTER NC flag signals BASIC line 093E ME ENT 1 makes room for new line 0958 ME ENT 3 copies into program and clears work space 0A3D PO RIGHT same as "PRINT OVER 1; CHR$32" statement 0F2C EDITOR enters line in main execution 0F81 ADD CHAR adds byte to line 0FA9 ED EDIT edit key puts in editing area 0FF3 ED DOWN next line number found 1031 ED EDGE checks for start of line 103E ED EDGE 1 addresses consecutive characters in 1059 ED UP line numbers checked 10A8 KEY INPUT edit or INPUT line copied to screen 111D ED COPY prints line in lower screen 1150 ED BLANK blanks out old line in lower screen 117C ED C DONE exit after line copied 11A7 REMOVE FP removes FP numbers from line 12AC MAIN 2 calls EDITOR to write line 12CF MAIN 3 sorts program lines from direct commands 1303 MAIN 4 reports after command line executed 133C MAIN 5 line/statement number included in report 1376 MAIN 7 store CONTINUE line/statement number 155D MAIN ADD adds line to program 157D MAIN ADD1 copies line from work space into program 168F LINE ZERO holds zeroes for line number 1691 LINE NO A use zero if no suitable line number 1795 AUTO LIST evaluates line number etc for each line 17CE AUTO L 1 find first line to show on screen 17E4 AUTO L 3 collect first line to show on screen 17ED AUTO L 4 skipped if scroll needed for current line 181F LIST 4 handles line number in LIST xxxx 1822 LIST 5 finds line start for listing 1835 LIST ALL loop to list BASIC lines 1855 OUT LINE prints out line 1865 OUT LINE1 prints line number 1894 OUT LINE4 loop to print each command of line 18B4 OUT LINE6 line print finished 190F LN FETCH finds number of line 191C LN STORE puts line number in system variable 1925 OUT SP 2 prints whole line 192B OUT SP 1 prints digit of line number 196E LINE ADDR finds address of line start from number 1974 LINE AD 1 checks number found with number given 1980 CP LINES compares line numbers 198B EACH STMT finds D'th statement 1990 EACH S 1 looks at each statement 1998 EACH S 2 finds end of statement 19AD EACH S 5 loop at end of statement 19B1 EACH S 6 checks for end of line 19B8 NEXT ONE find start of next BASIC line 19D5 NEXT O 3 skip line number in reading BASIC 19D6 NEXT O 4 get length of BASIC line 19DB NEXT O 5 first byte of next line found 19FB E LINE NO reads line number in editing area 1B17 LINE SCAN checks each statement for syntax 1B28 STMT LOOP loop to handle statements 1B29 STMT L 1 identifies and executes each statement 1B76 STMT RET end of statement execution 1B7D STMT R 1 check for new line execution 1B8A LINE RUN entry point for execution of line 1B9E LINE NEW jump to other than next line 1BB3 LINE END goes to next line unless program finished 1BBF LINE USE prepares to execute next line 1BD1 NEXT LINE reads line for interpretation 1BEE CHECK END checks for end of statement 1BF4 STMT NEXT finds next statement or next line 1C11 CLASS 05 save address of line start 1C96 PERMS changes colours as directed by current stmt 1CDE FETCH NUM checks for end of line 1CF0 IF skips line if false 1D00 IF 1 executes next statement if true 1D03 FOR loop values for statement already on stack 1D34 F L&S gets line and statement number 1D64 F LOOP checks each line in program 1D7C F FOUND line holding NEXT found 1D86 LOOK PROG checks for more statements in line 1D8B LOOK P 1 checks each line in program 1DA3 LOOK P 2 checks each statement in line 1DAB NEXT looping line and statement number found 1DEC READ 3 move along READ statements 1DED READ check if another DATA statement required 1E0A READ 1 get pointer to READ statement 1E27 DATA handling DATA statements 1E2C DATA 1 check end of statement 1E37 DATA 2 passed by in run time 1E39 PASS BY skips DEF FN or DATA statements 1E42 RESTORE operand read as line number 1E45 REST RUN put DATADD before line start 1E5F CONTINUE jumps to line/stmt in OLDPPC/OSPCC 1E67 GO TO finds next line (statement 0) to execute 1E73 GO TO 2 finds next line number to be executed 1EED GO SUB increments statement number 1F23 RETURN line and statement number from GO SUB stack 1F60 DEF FN passed by in run time 219B IN VAR 6 find length of line 21AF IN NEXT 1 considers INPUT statement 21E1 CO TEMP 1 look at next byte in statement 268D S BIN copies FP number into line 27BD S FN SBRN finds user-defined function in BASIC line 28FD V RUN look for vble in execution of line 294B V END after vble search, CH ADD addresses next code in BASIC line 2996 STK VAR called from DIM just to check line syntax 29AE SV ARRAYS checks line for subscript 29C3 SV COMMA finds subscript error if line executed 29D8 SV CLOSE line may still call for slicing 2AFF LET for new variable, DEST points to line 2C9B DEC TO FP numbers in line converted to FP form 2D3B INT TO FP integers in line converted to FP form BASIC program see program BASIC statement see BASIC line BC SPACES subroutine 0030 Makes spaces in the work space. The 1655 MAKE ROOM subroutine will make spaces anywhere in the RAM, moving up the calculator stack etc and resetting the pointers. But space is sooften required specifically in the work space that this restart routine is worth having. An empty workspace as set by 16B0 SET MIN has zero length: 5C61 WORKSP and 5C63 STKBOT hold the same address, preceded in memory by a newline and 80-byte marking the end of the editing area. MAKE ROOM operates by LDDR, and the new "space" isn't blanked; so the "space" made by this subroutine is actually a copy of the following bytes. Because of the DEC HL near the start of 169E RESERVE this space is always inserted_before the last byte in the workspace. If five spaces are made in an empty workspace, the result will be (the new bytes are underlined) ... NL_80_a_b_c_d 80 A B C D E where "a" is at the address in 5C61 WORKSP, and A B C D E are the first five bytes of the calculator stack; the NL and first 80-byte are the end of the editing area, a b c d are copies of AB C D. Further calls to BC SPACES will again copy the last byteof the work space; it will always be an 80-byte unless it is overwritten at some stage, or until 16B0 SET MIN is called to delete the work space altogether. Input parameters: BC holds the number of bytes space required; it mustn't be zero! Action: stack the number required and the address from 5C61 WORKSP and jump on to RESERVE. _169E_RESERVE (it cannot be called direct, as implied by the header, because it POPs bytes before its RET): get the top of the work space from 5C63 STKBOT - move back one byte; to the 80-byte in the editing area, or the last byte of the work space - call 1655 MAKE ROOM to make BC spaces below this pointer - restore 5C61 WORKSP; if the workspace was empty its start address will have been moved up by MAKE ROOM - (HL was left by the LDDR in MAKE ROOM pointing to the byte before the new spaces, NL in the example) increment HL twice and transfer it to DE; now DE points to the first byte of the new space, "a" in the example - similarly point HL at the start of the calculator stack. Exit: RET from RESERVE. Output parameters: BC unchanged: HL and DE as described above. Called from: 0621 SA SPACE 08B6 ME CONTRL 211C IN PR 2 255D S SC ROWS 25BE S Q AGAIN 2634 S INKEY$ 2B72 L DELETE$ 359C strs-add 35C9 chrs 35DE val 361F str$ 3645 read-in BE AGAIN 03F2 (03B5 BEEPER) Jumps from: 03D6 BE H&L LP BE END 03F6 (03B5 BEEPER) Jumps from: 03D6 BE H&L LP BEEP key (D7) see also commands, functions and operators, KEYBOARD SCANNING, 0246 extended mode table (c) The Z key in E mode with either shift produces the command BEEP. The command must be followed by two numeric expressions, separated by a comma. It is read by 1B29 STMT L 1 referring through the syntax offset table 1A48 to the syntax parameter table at 1A7A. 1AE3 P BEEP collects the parameters by 1C7A CLASS 08, then causes a jump via 1C10 CLASS 00 and 1C16 JUMP C R to the executive routine 03F8 BEEP. BEEP subroutine 03F8 see also timing Calculates a beep of given pitch and duration.The actualbeep is executed by 03B5 BEEPER, into which this routine exits. Only used to execute the BEEP command; can be called from m/c, but it is simpler to call 03B5 BEEPER direct.
