ugBASIC User Manual

   = x OR y

Performs a logical exclusion on two expressions, as a bitwise exclusion. For comparisons managed as a boolean result (TRUE or FALSE), result is TRUE if both expresions evaluate differently each other. The following table shows how result is determined:

'TRUE XOR TRUE = FALSE' 'TRUE XOR FALSE = TRUE' 'FALSE XOR TRUE = TRUE' 'FALSE XOR FALSE = FALSE'

Generally speaking, the XOR operator performs a bitwise comparison of the bits of two numeric expressions and sets the corresponding bit in result according to the previous table.

Note that ugBASIC uses the convention, very common in BASICs of the 1970s and 1980s, of considering Boolean logic as implemented through the so-called “two's complement”.

In other words, the value FALSE is associated with a number composed of all 0s, in terms of bits. The value TRUE is, instead, associated with a number composed of all 1s, again in terms of bits. According to the 2's complement representation, a number composed of all ones is always equivalent to the number -1, regardless of how many bits the number is composed of, while a number composed of all zeros is always equivalent to zero.

According to this convention, there is a coincidence between bitwise and logical operations: in fact, a bitwise XOR, applied to all the bits of the number, will be equivalent to the logical operation. Note that the XOR operator always evaluates both expressions, which can include executing routine calls.

Because the logical and bitwise operators have lower precedence than other arithmetic and relational operators, all bitwise operations must be enclosed in parentheses to ensure accurate results.

If the operands consist of a SIGNED BYTE expression and a numeric expression, converts the SIGNED BYTE expression to a numeric value (-1 for TRUE and 0 for FALSE) and performs a bitwise operation. So, the data type of the result is a numeric type appropriate for the data types of both expressions.

  IF x XOR x THEN: PRINT "never executed" : ELSE : PRINT "always executed": ENDIF

 Xr

• Atari (400/800)
• Atari XL/XE
• Commodore 128 (MOS 8502)
• Commodore 128 (Zilog Z80)
• Commodore 64
• Commodore 64+REU
• TRS-80 Color Computer
• TRS-80 Color Computer 3
• ColecoVision
• Amstrad CPC 664
• Dragon 32
• Dragon 64
• Thomson MO5
• Thomson MO5
• Olivetti Prodest PC128
• Commodore PLUS/4
• SEGA SC-3000
• SEGA SG-1000
• VG-5000
• Commodore VIC-20
• ZX Spectrum 48

If you have encountered a problem using this command, if you think there is a bug or the explanation is unclear, please open an issue for this keyword on GitHub. Thank you!