Remote Processing BASIC for the CX-10 Modbus - Manual (Page 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.
RELATED 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