Rockwell-automation 2708-NBD VBASIC Language Development Kit Uživatelský manuál stáhnout pdf (Strana 60)

A-B VBASIC and Visual BASIC

Appendix B

Differences Between

B–12

OPEN “COM” FOR INPUT AS #1 ‘Must be a normal terminal.

DO WHILE LOC(1) = 0: LOOP ‘Wait for any data in the buffer

R$ = INPUT$(1, #1)

Rx$ = Rx$ + R$

i = INSTR(Rx$, CHR$(13)) ‘Look for a carriage return.

IF i > 0 THEN

Datain$ = LEFT$(Rx$, i – 1) ‘Read in data

CLS

PRINT Datain$; ‘Display it

Rx$ = “”: R$ = “” ‘Clear the temporary buffer

END IF

LOOP

LOCATE[row][,[column][,[cursor]]]

Moves the cursor to the specified position. The start and stop arguments do

not apply to A-B VBASIC.

LOCATE 2, 1 ‘Position cursor on line 2

PRINT “Hello world”; ‘Use of semicolon prevent scrolling

LOCATE 1, 1, 0 ‘Position cursor on line 1

PRINT “Goodbye world”;

LOF(filenumber)

Returns the length of the named file in bytes. The REMARKS paragraph in

the VBDOS manual applies only to some A-B VBASIC devices. See the

chapter on Special Devices for details about specific devices.

OPEN “POWER” FOR INPUT AS #1

IF LOF(1) > 0 THEN ‘If file contains data,

Powerfail = TRUE then there must have been a power failure

ENDIF

LTRIM$(stringexpression)

Returns a copy of a string with the leading spaces removed.

A = 100

A$ = LTRIM$(STR$(A)) ‘Removes leading space in front of 100.

MID$(stringexpression, start[, length])

Returns a substring of a string. See VBDOS manual for detailed

information. See also MID$ statement, (replaces a portion of a string

variable with another string.)

A$ = “Now is the time for...”

B$ = MID$(A$, 8, 3) ‘B$ now equals “the”.

MKD$, MKI$, MKL$, MKS$

(MKD$ is no longer supported) Converts numeric values to string values.

See VBDOS manual for detailed information.

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