1401 Tiny Basic Manual

Release Number: 02, February 8, 2015

Author:
	Paul Laughton
	paul@laughton.com
	Please report any abnormal behaviors

Operation
	Basic files maybe stacked one on top of the other in the card
	reader. Each source file must be terminated with an END statement.
	When that END card is encountered, the Basic program is executed. 
	When the program terminates by executing the END card, Basic will 
	Halt. Pressing start (or Continue Program in the simulator) will 
	cause the next program to be loaded and executed.
	The normal halt I address is 5520. Please report any other halt 
	locations.
	If a Basic program runs away in infinite loop: Press Stop, turn
	Sense Switch B on, press Start. The program will Halt. Turn Sense 
	Switch B off and press Start for the next program. (Note: It is not 
	possible to manually Stop the simulator. To prevent simulator lock 
	up, a Basic program will self-terminate after executing 999 
	statements.

Numeric Expressions
	<nv> = Numeric Variable
		The <nv>s are the single letters A through Z.
		<nv>s contain 10 digit, signed numbers
		<nv>s initially have a value of 0.
	<nc> = Numeric Constant
		From 1 to 10 digits, 0 – 9
		Example: 0, 123, 123456789
	<nop> = Numeric Operator listed in order of precedence
		- is Unary Minus when in front of <nv>,<nc> and (<ne>)
		( ) are grouping parenthesis
		* is multiply
		/ is divide
		+ is add
		- is subtract when between two <nv>, <nc> or <ne>
		.LT. is the logical less than
		.EQ. is the logical equal
		.GT. is the logical greater than
		Note on printing operators on the 1403. The CHM print chains
		will print:
			= as #
			+ as &
			( as %
			) as ¤
	<ne> = Numeric Expression created using <nv>,<nc> and <nop>
		Example:	647 + B * -(C * 8)/4
		The operator precedence determines expression processing
	Logical Numeric Operations
		The three logical operators compare the <ne> to the left of
		logical operator with the <ne> to the right of logical
		operator. The compare results in a numeric value of 1 or 0
		The 1 value represents true.
			<ne> logical operator <ne>
		Example:
                        LET A = 1+2 .GT. 3+4
                        PRINT A will print 0
                        LET B =  1+2 .LT.. 3+4
                        PRINT B will print 1

String Expressions
	<sv> = String Variable
		<sv>s are A$ through Z$
		<sv>s may be up to 99 characters in length
		<sv>s are initialized to a single blank character
	<lit> = Literal
		'ANY CHARACTERS'
	<ns> = A number that Basic changes into a string for use in a <se>
		The conversion changes the 10 digit number into an 11 digit
		string. The 11th character will be – if the number’s value is
		negative otherwise the 11th character will be blank.
	<sop> = String Operator
		+ is the concatenation operator
			Example: LET C$ = A$ + B$
			Appends C$ to A$ and assigns the result to C$
	<se> = String Expression
		<sv>s, <lit>s and <ns> with the + (concat) operator
		Example: 'ABC' + D$ + -136
	Substring
		Any portion of a <sv>,<lit> or <ns> can be selected to be
		used in a <se>. The portion is selected with the expression
		(start <ne>,length <nv>|<nc>).
		Examples:
			'1234'(1+1,2) selects 23
			LET A$ = 'CBD'
			A$(2,1) selects 
			1234(9,2) selects 34 (think about this one)
		Note: A <ne> can be used for the start position but only 
		<nv> or <nc> can be used for the length.
	
Key words
	END (No parameters)
		Must be last card in deck. Terminates running program when
		executed

	FOR <nv> = start  <ne> , limit<ne> , step <ne>
		Examples: 
			FOR I = 1, 10, 2
			FOR J = 10, 1, -1
		The code following FOR will be always be executed once
		regardless of the value of limit <ne>.
		FOR/NEXT may be nested up to 10 deep

	NEXT (No parameters)
		Pared with latest FOR executed
		Error if not current FOR

	GOTO line number <ne>
		Example: GOTO 50
		Example: GOTO A + 10

	GOSUB line number <ne> 
		Example: GOTO 100
		GOSUBs may be nest up to 10 deep

	RETURN (no parameters)
		Pared with the latest GOSUB

	IF 
		<ne> <lop> <ne>, goto <ne>
		<se> <lop> <se>, goto <ne>
		<lop> is .LT. or .EQ. or .GT.
		If the result of the compare is true then goto <ne> line 			will be executed next. Otherwise the next sequential 			line will be 	executed.
		Examples:
			IF 'ABC'(1,1) .LT. 'ABC'(2,1), 100
			The statement at line 100 will be executed
			IF 'ABC’(1,1) .GT. 'ABC'(2,1), 100
			The statement following this line will be executed
       
	PRINT <se>
		Prints the <se>

	READ 
		Comma separated <nv>s or <sv>s
		Example: READ A,B$,D,F$
		The statement will read the values in the next DATA element 		into the variable. The variable type (<nv> or <sv>) must 			match the next DATA element type (<nc> or <lit>)

	DATA
		Comma separated <nc>s or <lit>s
		Data statements may appear anywhere in the program, either
		before or after the READ statements. It is, however, 			traditional to 	put them at the end of the program.
		EXAMPLE: DATA 127,'DEF',-167,'END'

	REM (anything following is ignored)
		REM is for comments
		REM statements are removed from the program at compile time.
		Do not GOTO of GOSUM to REM statement.