Remote-processing BASIC for the CX-10 Modbus Manual de usuario descargar pdf (Pagina 34)

BASIC PROGRAMMING GUIDE

2-25

IF THEN ELSE

Syntax: IF

expr

[ THEN ]

statement(s)

[ ELSE

statement(s)

]

Where:

expr

= any logical evaluation or variable

statement(s)

= any number of Basic statements

Function: When

expr

is TRUE (not zero), the instruction following THEN is executed, otherwise the

instruction following ELSE is executed.

Mode: Run

Use: 10 IF A<>B THEN PRINT "A=B" ELSE PRINT "A<>B"

DESCRIPTION

THEN is implied by IF. You may omit THEN. ELSE is optional. It is included when an "either - or"

situation is encountered.

In the case of multiple statements per line following an IF-THEN-ELSE, Basic executes the following

statements only if

expr

was true. This enables you to conditionally execute multiple statements with a single

expr

test. Remember this applies only to Basic statements separated by the {:} delimiter and on the same

program line.

expr

can be either a logical evaluation (=, <, >, <>, .AND., .OR., .XOR., or .NOT.) or a variable. Using a

simple variable as a flag can speed up program execution. The following examples illustrate different

execution speeds.

10 A = 1000

20 CLEAR TICK(0)

30 IF A<>0 THEN A=A-1 : GOTO 30

40 PRINT TICK(0)

The above program takes about 1 second to execute, which translates to about 1 ms/ line for this example. If

line 30 were re-written as:

30 IF A THEN A=A-1 : GOTO 30

Execution time is reduced by about 20% by taking away the "<>0" evaluation.

none

ERRORS

none

EXAMPLE

10 A = 1

20 IF A=0 THEN PRINT "A is 0" ELSE PRINT "A is non-zero"

>run

Is non-zero

1 2 ... 29 30 31 32 33 34 35 36 37 38 39 ... 83 84

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