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8086 TINY BASIC USER'S GUIDE INTRODUCTION The TINY BASIC language originated in the pages of Dr. DOBB'S JOURNAL and PEOPLE'S COMPUTER COMPANY in late 1975 and early 1976. Fed by the enthusiasm of early computer hobbyists and by the challenges and oportunities created by the early microcomputer chips, the idea of a tiny basic interpreter quickly gained popularity and acceptance. The language was a stripped down version of the ever-popular Dartmouth BASIC with the proviso that it be "useful" with a minimum of then very expensive memory. Additionally, TINY BASIC had to be ROMable since mass storage at that time consisted of reels of teletype punch paper tape, often punched at the unbearably slow rate of ten characters per second. The TINY BASIC language supports a very limited subset of the Dartmouth BASIC language. It does not compare at all with the large floating point BASIC's that have been released for almost all eight bit microcomputer chips. It does not support strings. Then, why 8086 TINY BASIC? Well, the size is still small (2700 bytes), it is efficient and easy to learn, and it is still ROMable. All of this implies that the language is still useful in at least two important applications: education and dedicated control. The present version of TINY BASIC is based on Li-Chen Wang's Palo Alto 8080 TINY BASIC as published in the May 1976 issue of DR. DOBB'S JOURNAL. Dr. Wang's version of TINY BASIC was chosen for its remarkable resiliance and simplicity. It has been optimized for the 8086 and it takes advantage of the hardware multiply and divide that the 8086 affords. Other enhancements include the use of the host operating system's line editing facilities and the LOAD and SAVE facilities, which, in the 8080 version, are due to unknown authors. The 8086 implementation is due to Michael E. Sullivan of Financial Software, 54 Grove Street, Haddonfield, NJ, 08033. THE LANGUAGE Numbers In TINY BASIC, all number are integers and must be within the range of -32767 .. 32767. 1 Variables There are 26 scalar variables donoted by the letters A through Z. The one array variable is denoted by '@(I)'. Its dimension is limited by the size of the TINY BASIC program. See the description of the SIZE function. Functions There are five functions in TINY BASIC. ABS(X) - Returns the absolute vaulue of the variable X. INP(X) - Returns data read from input port X. (0<=X<=255) PEEK(X)- Returns the contents of memory location X. (-32767<=X<=32767) RND(X) - Returns a random number between 1 and X (inclusive). SIZE - Returns the number of bytes left unused by the program. Arithmetic and Comparison Operators The following operators are supported: / - integer divide (fractional results not returned) * - integer multiply - - subtract + - add > - compare if greater than < - compare if less than = - compare if equal to NOTE: multiple assignment statements are not supported, i.e., "LET A=B=O" is interpreted by TINY BASIC as meaning "set A to the result of comparing B with O". # - compare if not equal to >= - compare if greater than or equal to <= - compare if less than or equal to The +,-,*, and / operations return a value within the range -32767 .. 32767. TINY BASIC works exclusively with decimal numbers. In order to represent the full range of numbers between 0 and 0FFFFH the 2 properties of two's complement arithemtic should be understood. For example, in order to PEEK at memory location 0FFFFH, the parameter -0 should be used as the PEEK function argument. Notice that the PEEK operation (as well as other address referenced operations) are all relative to the current data segment, which should be the same as the code segment. All compare operations result in a 1 if the comparison is true and a 0 if it is false. Expressions Expressions are formed with numbers, variables, and functions with arithmetic and compare operators between them. + and - signs can also be used at the beginning of an expression. The value of an expression is evaluated from left to right, except that the * and / operators are always given precedence, with + and -, and then the compare operators following, in that order. Parentheses can be used to alter the order of evaluation in the standard algabraic sense. Statements A TINY BASIC statement consists of a statement number between 1 and 32767 followed by one or more commands (see Commands below). Commands in the same statement are seperated by a semi-colon ";".If the "GOTO", "STOP", and "RETURN" commands are used then they must be the last command in that statement. Program A TINY BASIC program consists of one or more statements. When the direct command (see Direct Commands below) "RUN" is issued, the statement with the lowest statement number is executed first, then the one with the next lowest statement number, etc. The "GOTO", "GOSUB", "STOP", and "RETURN" commands can alter this normal sequence. Within any statement the execution takes place from left to right. The "IF" command can cause remaining commands within the same statement to be skipped. Abbreviations and Blanks TINY BASIC statements and commands may use blanks freely, except that numbers, command key words, and function names may not have embedded blanks. All TINY BASIC command key words and function names may be abbreviated by following the abbreviation with a period. For example, "PR.", "PRI.", and "PRIN." all stand for "PRINT". The word "LET" in the LET command may be ommited. 3 Editor TINY BASIC contains a useful text editor for entering and correcting TINY BASIC programs. All of the line editing features of the host operating system are used. In order to correct an existing TINY BASIC statement, that statement must be re-entered. Statements may be deleted by simply typing their statement number, followed by a CR. Corrections may be verified by typing LIST nnnn and striking the control-X key to terminate the LIST process. ERROR MESSAGES There are only three error messages in TINY BASIC. When an error is encountered the error message itself is printed, followed by the statement causing the program error with a "?" inserted at the point where the error is detected. Control is then passed to the TINY BASIC monitor. A synopsis of the three error conditions follow. -- WHAT? WHAT? 210 P?TINT "THIS" WHAT? indicates that TINY BASIC did not understand the statement or command. In the example above, the command PRINT was mistyped on statement number 210. -- HOW? HOW? 260 LET A=32000+5000? HOW? indicates that TINY BASIC understands but cannot execute the statement or command. In the example above, the sum of the numbers exceeds 32767. -- SORRY SORRY SORRY indicates that TINY BASIC understand but cannot execute the statement or command due to insufficient memory. One cure is to rephrase the TINY BASIC program in acceptable abbreviations. 4 STATEMENT COMMANDS TINY BASIC statement commands are listed below with examples. Remember that commands can be concatenated with semi-colons. In order to store any given statement, you must precede that statement with a statement number between 1 and 32767. Statement numbers are NOT shown in the examples. LET command LET A=234-5*6;A=A/2;X=A-100;@(X+9)=A-1 The LET command assigns the value of an expression to the specified variable. In the example above, the variable "A" assumes the value of the expression "234-5*6", or "204". Then the variable "A" assumes the value "102". Next, the variable "X" is set to the value of the expression "A-100", or "2". The last command assigns the value "101" to the array variable "@(11)". The "LET" portion of the LET command is optional, i.e., the following examples are true: A=10 C=5*3/5;C=C*5 REM Command REM ANYTHING CAN BE WRITTEN AFTER "REM" The REM command is ignored by TINY BASIC. It is used by experienced programmers to comment BASIC programs. A program comment is used by programmers to remind themselves of the logic of a program section. All good programs are invariably commented. PRINT Command PRINT PRINT will cause a carriage-return (CR) and a line-feed (LF) on the output device. PRINT A*3+1,"ABC" This form of the PRINT command will print the value of the expression A*3+1 on the output device, followed by the string ABC on the same line. Note that single (') or double quotes (") may be used to denote character strings, but that pairs must be mached. PRINT A*3+1,"ABC", This form of the PRINT command will produce the same results as the previous example except that the normal CR-LF is inhibited by the trailing comma at the end of the statement. This allows other PRINT 5 commands to print on the same line. PRINT A,B,#3,C,D,E,#10,F,G This form of the PRINT command demonstrates format control. The format character # is used to indicate the number of leading spaces to be printed before a number. The default number is 6. Once the # format is invoked it is active for the remainder of the statement unless overridden by a subsequent format specifier, as in the example. PRINT 'ABC',\,'XXX' The back-slash (\) character is used to cause a CR without a LF. In this example, the string ABC is printed followed by the string XXX on top of the original ABC. INPUT Command INPUT A,B The INPUT statement is used to acquire input data during program execution. In the example above, TINY BASIC will print A: and wait for a number to be typed at the console terminal. Next, TINY BASIC will print B: and wait for another number to be typed at the console terminal. In this example the variables A and B will assume the values of the appropiate input values. The INPUT statement will accept expressions as well as numbers as input. INPUT 'WHAT IS THE WEIGHT'A,"AND SIZE"B In this example TINY BASIC will print the string WHAT IS THE WEIGHT: and wait for operator input. Next, the string AND SIZE: will be printed, on the same line, and TINY BASIC will wait for operator input. INPUT A,'STRING',\,"ANOTHER STRING",B TINY BASIC will react to the back-slash character (\) in this example in the same fashion as in the PRINT command. The second string will overwrite the first string STRING. IF Command IF A<B LET X=3;PRINT 'THIS STRING' The IF command works with the comparison operators (enumerated above) to check the validity of the specified comparison condition. In this example, if the comparison A<B is true, then the balance of the commands in the statement are executed. However, if the comparison tests false, then the balance of the commands in the statement are NOT executed and control passes to the statement with the next highest statement number. 6 IF A<B GOTO 100 This example illustrates a common use of the IF command and the GOTO (see below) command. If the comparison tests true control is passed to statement number 100, otherwise execution passes to the statement with the next highest statement number. GOTO Command GOTO 120 This statement is used to modify the normal sequence of execution of TINY BASIC statements. In this example, control is passed unconditionally to statement number 120. The GOTO command cannot be followed by a semi-colon and other commands within the same statement. It must appear as the last command in any given statement. GOTO A*10+B This form of the GOTO is called a "computed GOTO". In this case, control is passed to the statement number represented by the expression that follows "GOTO". GOSUB Command GOSUB 120 The GOSUB command is used to invoke a subroutine at the specified statement number (120 in the example). Control is passed to statement number 120 and execution continues. A RETURN command (see below) is used, within the subroutine, to cause TINY BASIC to pass control to the statement that immediatly follows the GOSUB command that caused the subroutine to execute. The GOSUB command cannot be followed by any other commands within the same statement and it must be the last command within any given statement. GOSUB commands can be nested, limited by the size of the stack space (see below). GOSUB A*10+B In this example, the subroutine at the statement number equal to the value of the expression is executed. This form of the statement will cause a different subroutine to be executed depending upon the value of the expression that follows "GOSUB". RETURN Command RETURN The RETURN command causes execution to resume at the statement that follows the GOSUB that caused the current subroutine to be executed. It must be the last command of any given statement. 7 FOR Command FOR X=1 TO 10 PRINT 'HELLO' NEXT X The FOR command is used to set up execution loops. In the TINY BASIC program segment above the statement PRINT 'HELLO' is executed 10 times since it is placed between the FOR statement and the NEXT statement. The NEXT X statement (see below) has the effect of incrementing X by one and passing control to the FOR statement. If the new value of X is still less than or equal to 10, the TINY BASIC statements between FOR and NEXT are executed again. This process repeats until X is incremented past the loop termination value (10 in the example above). FOR X=1 TO 10 STEP 2 PRINT 'HELLO' NEXT X In the above variant of the FOR command the loop increment has been changed from 1 (the default) to 2 by means of the STEP clause. In this case, the program fragment would only print HELLO five times if executed. FOR commands can be nested, that is, one FOR loop can contain other FOR loops provided that the loop variables (the variable X in the examples) are diferent,. If a new FOR command with the same loop variable as that of an old FOR command is encountered, the old FOR will be terminated. NEXT Command NEXT X The NEXT command is part of the FOR command and is used to cause loop variables to be incremented by the increment specified by the STEP clause (default is 1) and to pass control to the appropiate TINY BASIC FOR loop. The variable specified by the NEXT command (X in the example) is used to specify the correct FOR loop. POKE Command POKE A,B The POKE command is used to place data B into memory address A. This command may be repeated as follows: POKE A,B,C,D In the above example, data B is placed in memory location A, then data 8 D is placed in memory location C. All variables may be expressions. Be careful not to POKE TINY BASIC itself! USR Command USR(I,J) The USR Command is actually a built-in TINY BASIC subroutine call that permits linkage to machine language subroutines. All 8086 registers are available for use by the machine language subroutine. It is the responsibility of the machine language routine to execute a RET instruction. In the example above, a machine language routine at address I is called. J is an optional parameter that, if present, will be passed in register BX to the subroutine. WAIT Command WAIT I,J,K The WAIT command is used to cause TINY BASIC execution to pause and wait for a specified value at an 8086 input port. In the example above, the value at input port I is read, exclusive OR'd with the value of the expression J, and the result is then AND'd with the value of expression K. WAIT will return only if the final result is non-zero. WAIT provides an easy-to-use mechanism to cause TINY BASIC to pause its execution and wait for a specified external event. J is assumed to be 0 if not specified. STOP Command STOP This command stops the execution of a TINY BASIC program and passes control to the TINY BASIC monitor. It can appear many times in a program but it must be the last command in any given statement. DIRECT COMMANDS Direct commands are those commands that can be invoked only by the operator when TINY BASIC is in command mode (i.e. in response to the '>' prompt). All statement commands (those listed above) can be invoked while in command mode. Typing a control-C while in command or monitor mode will cause TINY BASIC to terminate. Control is then passed to the host operating system monitor. Recall that a statment consists of a statement number followed by one or more commands. If the statement number is missing, or if it is 0, the command will be executed immediatly after typing the 9 terminating CR. The following commands can be used as direct commands; they CANNOT be used as part of a TINY BASIC statement. RUN Command RUN The RUN command causes execution of the stored TINY BASIC program. Execution will commence at the lowest numbered statement and continue until there are either no more statements to execute or a STOP command is found. A long TINY BASIC program may be terminated by typing control-X at the console. This passes control the the TINY BASIC monitor. A control-C may be typed at any time also, then TINY BASIC is terminated and control is passed to the host operating system. LIST Command LIST The LIST command is used to display the current TINY BASIC program on the operator's console. The statements will be listed in numerical order. If LIST is followed by an expression (e.g. LIST 200) the listing will commence with statements following the specified statement, inclusive. NEW Command NEW The NEW command deletes the current program from TINY BASIC's memory. SAVE Command SAVE FILENAME The SAVE command saves the current TINY BASIC program on the logged in disk with the specified filename FILENAME. The default filetype is ".TBI". If there is insufficient room on the disk, the SAVE command responds with "HOW?". LOAD Command LOAD FILENAME The LOAD command loads the specified TINY BASIC program from the logged in disk into the program area. Any program residing within TINY BASIC prior to the LOAD operation is lost. If the specified program is not found on the disk, or if there is insufficient room for the 10 program, LOAD responds with "HOW?". The filetype is assumed to be ".TBI". BYE Command BYE The BYE command terminates TINY BASIC. Control is passed back to the host operating system. TINY BASIC OPERATION TINY BASIC is initiated from the host operating system's command mode like any other transient command. TINY BASIC will sign-on, announce 'OK', and then prompt '>' awaiting operator interaction. An example follows: A:TBASIC 8086 TINY BASIC V1.0 OK > In the example above the program 'TBASIC.COM' was found on the logged-in disk ('A' in the example). TINY BASIC then commenced execution by first announcing itself and then prompting '>' for operator input. TINY BASIC utilizes all of the host operating system's line editing facilities. For example, if an operator wished to cancel a line typed to TINY BASIC, he need only type a control-X, etc. If hard copy of a TINY BASIC session is desired, control-P and control-N will toggle the printer, if it exists. At present, saved TINY BASIC programs can be edited only with the internal TINY BASIC editor. Programs prepared by an external editor can not be read by TINY BASIC. 11 əsupported: / - i