LOCAL

Action

Dimensions a variable LOCAL to the function or sub program.

 

 

Syntax

LOCAL var As Type

 

 

Remarks

Var	The name of the variable
Type	The data type of the variable.

 

There can be only LOCAL variables of the type BYTE, INTEGER, WORD, DWORD, LONG, SINGLE, DOUBLE or STRING.

 

A LOCAL variable is a temporary variable that is stored on the frame.

When the SUB or FUNCTION is terminated, the memory will be released back to the system.

A Sub/Function is full reentrant which means that it can be called recursively. Because of this, local memory is dynamic and not static as global variables.

BIT variables are not possible because they are GLOBAL to the system.

 

The AT , ERAM, SRAM, XRAM directives can not be used with a local DIM statement. Also local arrays are not possible.

 

Notice that a LOCAL variable is not initialized. It will contain a value that will depend on the value of the FRAME data. So you can not assume the variable is 0. If you like it to be 0, you need to assign it.

A normal DIM-med variable is also not initialized to 0. The reason all variables are 0 (and strings are ""), is that the RAM memory is cleared. With the $NORAMCLEAR option you can turn this behaviour off.

So to conclude, a LOCAL variable will behave the same as a normal variable with the $NORAMCLEAR option enabled.

 

 

While it would be simple to initialize the LOCAL variables to 0, in most/all cases, you will assign a value to it anyway, so it would be a waste of code space.

 

See also

DIM

 

 

ASM

NONE

 

 

Example

'-----------------------------------------------------------------------------------------
'name : declare.bas
'copyright : (c) 1995-2005, MCS Electronics
'purpose : demonstrate using declare
'micro : Mega48
'suited for demo : yes
'commercial add on needed : no
' Note that the usage of SUBS works different in BASCOM-8051
'-----------------------------------------------------------------------------------------
 
$regfile = "m48def.dat" ' specify the used micro
$crystal = 4000000 ' used crystal frequency
$baud = 19200 ' use baud rate
$hwstack = 32 ' default use 32 for the hardware stack
$swstack = 10 ' default use 10 for the SW stack
$framesize = 40 ' default use 40 for the frame space
 
 
' First the SUB programs must be declared
 
'Try a SUB without parameters
Declare Sub Test2
 
'SUB with variable that can not be changed(A) and
'a variable that can be changed(B1), by the sub program
'When BYVAL is specified, the value is passed to the subprogram
'When BYREF is specified or nothing is specified, the address is passed to
'the subprogram
 
Declare Sub Test(byval A As Byte , B1 As Byte)
Declare Sub Testarray(byval A As Byte , B1 As Byte)
'All variable types that can be passed
'Notice that BIT variables can not be passed.
'BIT variables are GLOBAL to the application
Declare Sub Testvar(b As Byte , I As Integer , W As Word , L As Long , S As String)
 
'passing string arrays needs a different syntax because the length of the strings must be passed by the compiler
'the empty () indicated that an array will be passed
Declare Sub Teststr(b As Byte , Dl() As String)
 
Dim Bb As Byte , I As Integer , W As Word , L As Long , S As String * 10 'dim used variables
Dim Ar(10) As Byte
Dim Sar(10) As String * 8 'strng array
 
For Bb = 1 To 10
Sar(bb) = Str(bb) 'fill the array
Next
Bb = 1
'now call the sub and notice that we always must pass the first address with index 1
Call Teststr(bb , Sar(1))
 
 
Call Test2 'call sub
Test2 'or use without CALL
'Note that when calling a sub without the statement CALL, the enclosing parentheses must be left out
Bb = 1
Call Test(1 , Bb) 'call sub with parameters
Print Bb 'print value that is changed
 
'now test all the variable types
Call Testvar(bb , I , W , L , S )
Print Bb ; I ; W ; L ; S
 
'now pass an array
'note that it must be passed by reference
Testarray 2 , Ar(1)
Print "ar(1) = " ; Ar(1)
Print "ar(3) = " ; Ar(3)
 
$notypecheck ' turn off type checking
Testvar Bb , I , I , I , S
'you can turn off type checking when you want to pass a block of memory
$typecheck 'turn it back on
End
 
'End your code with the subprograms
'Note that the same variables and names must be used as the declared ones
 
Sub Test(byval A As Byte , B1 As Byte) 'start sub
 Print A ; " " ; B1 'print passed variables
 B1 = 3 'change value
 'You can change A, but since a copy is passed to the SUB,
 'the change will not reflect to the calling variable
End Sub
 
Sub Test2 'sub without parameters
 Print "No parameters"
End Sub
 
 
Sub Testvar(b As Byte , I As Integer , W As Word , L As Long , S As String)
 Local X As Byte
 X = 5 'assign local
 B = X
 I = -1
 W = 40000
 L = 20000
 S = "test"
End Sub
 
Sub Testarray(byval A As Byte , B1 As Byte) 'start sub
 Print A ; " " ; B1 'print passed variables
 B1 = 3 'change value of element with index 1
 B1(1) = 3 'specify the index which does the same as the line above
 B1(3) = 3 'modify other element of array
 'You can change A, but since a copy is passed to the SUB,
 'the change will not reflect to the calling variable
End Sub
 
'notice the empty() to indicate that a string array is passed
Sub Teststr(b As Byte , Dl() As String)
Dl(b) = Dl(b) + "add"
End Sub

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