GCBASIC documentation
Variables Operations

Syntax:

    Variable = data

Explanation:
Variable will be set to data.
data can be either a fixed value (such as 157), another variable, or a sum.
All unknown byte variables are assigned Zero. A variable with the name of Forever is not defined by GCBASIC and therefore defaults to the value of zero.
If data is a fixed value, it must be an integer between 0 and 255 inclusive.
If data is a calculation, then it may have any of the following operands:

    + (add)
    - (subtract, or negate if there is no value before it)
    * (multiply)
    / (divide)
    % (modulo)
    & (and)
    | (or)
    # (xor)
    ! (not)
    = (equal)
    <> (not equal)
    < (less than)
    > (greater than)
    <= (less than or equal)
    >= (more than or equal)

The final six operands are for checking conditions. They will return FALSE (0) if the condition is false, or TRUE (255) if the condition is true.
The And, Or, Xor and Not operators function both as bitwise and logical operators.
GCBASIC understands order of operations. If multiple operands are present, they will be processed in this order:

    Brackets
    Unary operations (not and negate)
    Multiply/Divide/Modulo
    Add/Subtract
    Conditional operators
    And/Or/Xor

There are several modes in which variables can be set. GCBASIC will automatically use a different mode for each calculation, depending on the type of variable being set. If a byte variable is being set, byte mode will be used; if a word variable is being set, word mode will be used. If a byte is being set but the calculation involves numbers larger than 255, word mode can be used by adding [WORD] to the start of one of the values in the calculation. This is known as casting - refer to the Variables article for more information.

And with other operations

The order of operations, comparison operations have a higher precedence than boolean operations.  GCBASIC behaves the same way as most other languages.  Source code like this (randomly taken from glcd_ili9326.h) works.

if GLCDfntDefaultSize = 2 and CurrCharRow = 7 then

It is an easy mistake to compare values and get the precendent incorrect.  Generally, if you can use an individual bit check, that is generally the best way to go. These are a lot simpler for the compiler to deal with and result in much nicer assembly.

This works using the correct order of precendence.

    if (H_Byte & 0x10) = 0x10 Then ...

    'or, using the individual bit check to do the same
    if H_Byte.4 Then

This will fail as the order of precendence as shown below.

    if H_Byte & 0x10 = 0x10 Then ...

    'the code above equates. This is not achieve the testing of the H_byte.4
    if H_Byte & ( 0x10 = 0x10 ) Then ...

Divide or division

GCBASIC support division.

When using division you will get accurate results, within the limitations of integer numbers, by completing any multiplication first and the division last.   But, you may have issues with variables overflowing - ensure your variable type are correct for the calculation type.

If you that calculation a division, the compiler will use the long division routine, if the value may overflow, and then fit the result into a word.   This code provides the correct result, again within the limitations of integer numbers:

    dim L1s as word
    dim L1p as word
    L1s = 6547200 / L1p

Division also sets the global system variable SysCalcTempX to the remainder of the division.  However the following simple rules apply.

If you prefer, you can add Let to the start of the line.   It will not alter the execution of the program, but is included for those who are used to including it in other BASIC dialects.

Example:

    'This program is to illustrate the setting of variables.
    Chipmunk = 46        'Sets the variable Chipmunk to 46
    Animal = Chipmunk    'Sets the variable Animal to the value of the variable Chipmunk
    Bear = 2 + 3 * 5     'Sets the variable Bear to the result of 2 + 3 * 5, 17.
    Sheep = (2 + 3) * 5  'Sets the variable Sheep to the result of (2 + 3) * 5, 25.
    Animal = 2 * Bear    'Sets the variable Animal to twice the value of Bear.

    LargeVar = 321       'LargeVar must be set as a word - see DIM.
    Temp = LargeVar / [WORD]5 'Note the use of [WORD] to ensure that the calculation is performed correctly

Setting Explicit Bits of a Variable/Register:

GCBASIC supports the method setting a specific bit of a variable or register. Use the following method:

    'variable.bit method
    myByteVariable.0 = 1   'will set bit 0 to 1
    myByteVariable.1 = 0   'will set bit 1 to 0
    myByteVariable.2 = 1   'will set bit 2 to 1

To set more than one bit in one command GCBASIC supports the bits method.

GCBASIC also supports setting specific bits of a variable or register. Use the following method:

    'variable.bitS method
    SPLLEN, IRCF3, IRCF2, IRCF1, IRCF0 = b'01111'
    ' would generate ASM [for your specific microcontroller like the following.
    ' bcf OSCTUNE,PLLEN,ACCESS
    ' bsf OSCCON,IRCF2,ACCESS
    ' bsf OSCCON,IRCF1,ACCESS
    ' bsf OSCCON,IRCF0,ACCESS

This method is limited to literal values. You cannot use value from another variable as the setting value (at v0.98.00).

Setting Explicit Bits of a Variable/Register with Error Handling

To set more than one bit in one command GCBASIC supports the bits method.

GCBASIC also supports setting specific bits of a variable or register with error handling. Use this method to prevent errors when a specified bit does not exist.

The [canskip] prefix will handle the error condition when a specific bit or specific bits do not exist. The following example shows the usage.

    [canskip] SPLLEN, IRCF3, IRCF2, IRCF1, IRCF0 = b'01111'

This method is limited to literal values. You cannot use value from another variable as the setting value (at v0.98.00).

This example shows how the error handler compares to not have the [canskip] prefix

      ' Of these two lines, only the first compiles:
      [canskip] SPLLEN, IRCF3, IRCF2, IRCF1, IRCF0 = b'01111'    'first line with error handler
      SPLLEN, IRCF3, IRCF2, IRCF1, IRCF0 = b'01111'              'second line with no error handler

      'Second line produces this message:
      'samevar.gcb (16): Error: Bit IRCF3 is not a valid bit and cannot be set

Setting a String - set a string with Escape characters

An example showing how to set a string to an escape sequence for an ANSI terminal.  You can `Dim`ension a string and then assign the elements similar to setting array elements.

    dim line2 as string
    line2 =  27, "[", "2", "H", 27, "[","K"
    HSerPrint line2

Will send the following to the terminal. <esc>[2H<esc>[K

For more help, see: Variables