Intel 9800758-02 manual If-Then-Else, Input, Goto

BASIC-SO Commands and Statements

GOTO

The GOTO (line number) statement transfers execution of instruction lines from the current line to the line number specified. There is no provision for a return to the branching point.

GOTO line numberl GO TO line number

The GO TO in line 270 causes a jump to line 100.

250 IF EOF(6) THEN 300

260PRINT "FILE STILL CONTAINS DATA"

270GOTO 100

300PRINT "FILE ";F$;"IS OUTOF DATA."

310END

IF-THEN-ELSE

The IF-THEN-ELSE statement evaluates the given logical expression and executes the THEN instruction if true, the ELSE instruction if it is false. The ELSE instruc- tion is optional; if it is left out, and the logical expression is false, the next line is executed. Line numbers can be used in place of instructions and have the same effect as GO TOs. An IF statement must always be on one line. IF statements may also be nested, as shown in the example below. In this example, an ELSE clause matches the last unmatched THEN.

IF expression THEN instruction [ELSE instruction]

5 IF S$ =" "THEN 40

10IF S$ = "+" THEN A = A+B ELSE IF S$ = "-"THEN A=A-B ELSE 30

20GOT040

30PRINT"lnvalid S$"

40END

INPUT

The INPUT statement returns a prompt (question mark) and waits for the user to enter data. String literals or numeric values may be expected, according to the type of variable specified as an argument.

INPUT [quoted string;] variable [,variable] ...

If a string expression follows INPUT and is followed by a ";" it is used in place of the question mark as the prompt. If the number or type of data items in the response do not agree with the number or type of variables requested, BASIC-80 returns a prompt to re-enter the line. Strings which are input need not be surrounded by quotes as long as they do not contain commas (,). Leading and trailing blanks are ignored in this mode.

10 INPUT A,B,C

20PRINT(A+B+C)/5

30END

RUN

?40,2,18

12

Ok

6-9