J.E.Lawrie HINTS-15.
ODD JOTTINGS AND REMINDERS ON BASIC
ABBREVIATIONS To check that the printer is ready, include
IF GET(&E5) AND 1 THEN .......
CHAIN CH.
CLEAR CL. To print what is coming on the screen, include
DELETE DEL. OSCLI("CLI #+P~E"):dummy= INKEY(0)
ENDPROC E. ( not necessary to use "#-P" to switch off )
INPUT I.
LIST L. To delete a file from RAM
LOAD LO. *ERASE filename or :*//filename
NEXT N. (Use OSCLI if filename is a string variable)
PRINT P.
RENUMBER REN. To go to the Index when in Basic, using TAB key
RETURN R. IF INKEY(0)=9 THEN OSCLI("CLI #I"):dummy=INKEY(0)
STEP S.
LEFT$ LE. To empty the keyboard buffer
RIGHT$ RI. REPEAT UNTIL INKEY(0)=-1
MID$ M.
FALSE £ To hold at a line until a particular key is pressed
REPEAT UNTIL GET=32 (spacebar in this example)
or =CHR$(X)
To abort a program - reverts to the index
K=INKEY(secs*100):IF K=-1 OSCLI("CLI #I")
To move graphics on screen, with limits to the movement.
110 KEY=INKEY(0)
120 Y=Y-(1 AND KEY=225 AND Y>0)+(1 AND KEY=254 AND Y<7) for movement of
130 X=X+(1 AND KEY=253 AND X<85)-(1 AND KEY=252 AND X>5) graphics with
the arrow keys
-within limits.
33 ! 53 5 73 I 93 ] 113 q 9 TAB
34 " 54 6 74 J 94 ^ 114 r 13 ENTER
35 # 55 7 75 K 95 _ 115 s 32 SPACE
36 $ 56 8 76 L 96 ` 116 t
37 % 57 9 77 M 97 a 117 u 252 LEFT
38 & 58 : 78 N 98 b 118 v ARROW
39 ' 59 ; 79 O 99 c 119 w 253 RIGHT
40 ( 60 < 80 P 100 d 120 x ARROW
41 ) 61 = 81 Q 101 e 121 y 254 DOWN
42 * 62 > 82 R 102 f 122 z ARROW
43 + 63 ? 83 S 103 g 123 { 255 UP
44 , 64 @ 84 T 104 h 124 | ARROW
45 - 65 A 85 U 105 i 125 }
46 . 66 B 86 V 106 j 126 ~
47 / 67 C 87 W 107 k 127 (black square)
48 0 68 D 88 X 108 l
49 1 69 E 89 Y 109 m 160 ( hard space )
50 2 70 F 90 Z 110 n
51 3 71 G 91 [ 111 o 163 £
52 4 72 H 92 ` 112 p
IF F THEN ... is the same as IF F<>0 THEN ...
Error trapping
ON ERROR:dummy=INKEY(0):PROCerr:PRINT:REPORT:PRINT" in line ";ERL:END
a) DEFPROCerr:IF ERR=17 .............. ENDPROC ELSE ...........
or b) DEFPROCerr:VDU1,127,1,67,1,83:@%=&0002000A:ENDPROC
a) allows a deliberate escape from the program. Other errors
will not stop the program ( but it cannot carry on from
where the error occurred!).
b) stops the program after restoring the VDUs and print format.
Use of INSTR
110 REPEAT
120 A$=GET$
130 A= INSTR("1122334455667788=+.>IiAaDdSs Qq",A$)
140 UNTIL A>0
A keypress for A$ is checked against the contents of INSTR.
If a match is found then A returns a figure - in this case
from 1 to 32 else A=0
150 A=INT((A+1)/2) i.e in this example A can be from 1 - 16
( it allows upper and lower case ).
160 IF..
170 IF..
180 A=A-10:ON A GOTO 210,260,310 etc etc 850
(850 could be QUIT, matching Qq)
Print Format
Default print format instruction is @%=&90A which gives a
format of 9 digits in a field width of 10.
My preference is @%=&2000A to avoid decimals
or @%=&2020A to give two decimal places in a width of 10
Channel Error
In programs where a second attempt to open a channel
results in an error i.e CN has a positive value, use
IF CN<>0 (file is already open) THEN .......
Put this immediately after CN=OPENIN(" datafile ")
OSCLI Strings
Example -
110 b$=a$(J)
120 INPUT "RAM ?"R$
130 OSCLI("CLI #F|SV~D:RAM."+R$+"|EF"+b$+"~E~E|[")
Which means "go to the Filer,:RAM.(R$), and fetch from
EPROM the file b$)
All entries in the OSCLI must be in arrays.
LINE EDITOR
If the C.C.L line editor is saved as a file called LINEDIT
it can be added to the listing of a Basic program with the
command *CLI .*:*//LINEDIT
Carrying variables or numeric values within Basic
110 PROCshift(10) or PROCshift("TEN")
120 X$="SIX"
130 X=6
140 X$="FORTY"
150 X=40
...
300 DEFPROCshift(X) X will now be 10
or 300 DEFPROCshift(X$) X$ will now be TEN
IF F THEN ... means " IF F<>0 THEN ......
Logic Operators
a) U=U-(G=0) If G=0 this expression = -1 otherwise = 0
so, if G=0 then U=U+1 else U is unchanged.
b) U=U+6*(U=6) If U=6 it reduces the value by 6 otherwise
U is unchanged. Can be used when U is
increasing but at 6 it reverts to zero.
c) TAB(X+(R>9),0);R If R>9 it will appear on the screen
one space earlier.
8 8
9 is normal. Using the above we get 9
10 10
Basic 11 DIV 4 = 2 (the whole No.)
Maths 11 MOD 4 = 3 (the remainder)
RND(x) gives random Integers from 1 to x
RND(1) gives a number from 0 to .99999999....
TRUE is -1
FALSE is 0
PI = 3.1416.... EXP = 2.7183....
LN is the Natural Log of x, to the base e
LOG(x) is the Common Log, to the base 10
TAN(RAD(x)) gives the Tangent of x degrees
Y=RAD(X)*180/PI converts x radians to Y deg.
END
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