CONST

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Action

Declares a symbolic constant.

 

 

Syntax

CONST symbol = numconst

CONST symbol = stringconst

CONST symbol = expression

 

 

Remarks

Symbol

The name of the symbol.

Numconst

The numeric value to assign to the symbol.

Stringconst

The string to assign to the symbol

Expression

An expression that returns a value to assign the constant

 

Assigned constants consume no program memory because they only serve as a reference to the compiler.

The compiler will replace all occurrences of the symbol with the assigned value.

 

You can use a constant to give a value a more meaningful name.

For example :

 

variable = 1

const optHeaterOn = 1

variable = optHeaterOn

 

The source code is better to read when you assign a constant. Even better when the values change later, for example when HeaterOn becomes 2, you only need to replace 1 line of code.

 

 

See also

ALIAS

 

 

Example

'-----------------------------------------------------------------------------------------

'name                     : const.bas

'copyright                : (c) 1995-2016, MCS Electronics

'purpose                  : demo for constants

'micro                    : Mega48

'suited for demo          : yes

'commercial addon needed  : no

'-----------------------------------------------------------------------------------------

 

$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

 

'dimension some variables

Dim Z As String * 10

Dim B As Byte

 

'assign some constants

'constants dont use program memory

Const S = "test"

Const A = 5                                                 'declare a as a constant

Const B1 = &B1001

 

'or use an expression to assign a constant

Const X =(b1 * 3) + 2

Const Ssingle = Sin(1)

 

 

Print X

Print Ssingle

 

 

B = A

'the same as b = 5

 

Z = S

'the same as Z = "test"

 

Print A

Print B1

Print S

 

 

'you can use constants with conditional compilation

#if A = 5                                                   ' note there is no then

Print "constant a is 5"

#if S = "test"

  Print "nested example"

#else                                                   ' else is optional

#endif

#else

#endif

End