| Syntax:
| CLEAR
CLEARCOMMON
CLEARLOCAL
|
| Discussion:
|
The CLEAR statement initializes the variables defined in the
current Internet Basic program. String variables are initialized to null,
while numeric variables are initialized to binary zero.
There are three forms of the CLEAR statement:
- CLEAR initializes all variables defined in the program.
- CLEARCOMMON initializes just the COMMON
variables defined in the program.
Note: The Internet Basic compiler recognizes two versions of this
statement, one without a space (CLEARCOMMON) and one with a
space (CLEAR COMMON).
- CLEARLOCAL initializes just the LOCAL
variables defined in the program.
Note: The Internet Basic compiler recognizes two versions of this
statement, one without a space (CLEARLOCAL) and one with a
space (CLEAR LOCAL).
|
| Applications notes:
|
- Many applications packages use program "overlays" to break a
large task into smaller program segments. In these cases, one
program will simply run another program in the same memory
partition. This is sometimes called "chaining" of programs,
although this document refers to this as "overlaying"
programs.
It is often desirable to retain data from program to program
during the overlay process. This is most easily done with
COMMON data variables. But, it is also desirable to initialize
program variables with a single statement.
In these cases, the CLEARLOCAL statement is the best
alternative. It initializes just the LOCAL data variables
(while the values stored in the COMMON variables remain
unchanged from the preceding program running in the same
partition).
- You may use any number of CLEAR statements in a single
program.
- Sometimes, COMMON and LOCAL data variables may be used as a
way of organizing or segregating data within a single program.
In these cases, CLEARCOMMON or CLEARLOCAL perform
initialization tasks for a distinct group of variables without
affecting the other group.
|
| Example 1:
|
LENGTH 25 & LOCAL NAME$, ADDRESS$, CITYSTZP$
LENGTH 8.2 & LOCAL CRLIMIT, ARTOTAL, ARCURRENT
.
CLEAR
In the above example, the CLEAR statement initializes all of the
variables in the program, both common and local.
|
| Example 2:
|
LENGTH 25 & LOCAL NAME$, ADDRESS$, CITYSTZP$
LENGTH 8.2 & LOCAL CRLIMIT, ARTOTAL, ARCURRENT
LENGTH 5 & COMMON CUSTNO$
LENGTH 2.0 & COMMON PAGENUM
.
CLEARLOCAL
In this example, the CLEARLOCAL statement initializes just the
local variables in the program. The common variables, in this
case CUSTNO$ and PAGENUM, are not initialized by the CLEARLOCAL
statement.
|
