Designator: Declare word-sized symbol, word aligned/sized data, or read/write a word of main memory.

VAR
   WORD Symbol < [Count ] >

DAT
   < Symbol > WORD Data < [Count] >

((PUB ┆ PRI))
   WORD [BaseAddress] < [Offset ] >

((PUB ┆ PRI))
   Symbol.WORD < [Offset ] >

• Symbol is the desired name for the variable (Syntax 1) or data block (Syntax 2) or is the existing name of the variable (Syntax 4).
• Count is an optional expression indicating the number of word-sized elements for Symbol (Syntax 1), or the number of word-sized entries of Data (Syntax 2) to store in a data table.
• Data is a constant expression or comma-separated list of constant expressions.
• BaseAddress is an expression describing the word-aligned address of main memory to read or write. If Offset is omitted, BaseAddress is the actual address to operate on. If Offset is specified, BaseAddress + Offset * 2 is the actual address to operate on.
• Offset is an optional expression indicating the offset from BaseAddress to operate on, or the offset from word 0 of Symbol. Offset is in units of words.

Explanation

WORD is one of three multi-purpose declarations (BYTE, WORD, and LONG) that declare or operate on memory. WORD can be used to:

1. declare a word-sized (16-bit) symbol or a multi-word symbolic array in a VAR block, or
2. declare word-aligned, and/or word-sized, data in a DAT block, or
3. read or write a word of main memory at a base address with an optional offset, or
4. access a word within a long-sized variable.

Range of Word

Memory that is word-sized (16 bits) can contain a value that is one of 2¹⁶ possible combinations of bits (i.e., one of 65,536 combinations). This gives word-sized values a range of 0 to 65,535. Since the Spin language performs all mathematic operations using 32-bit signed math, any word-sized values will be internally treated as positive long-sized values. However, the actual numeric value contained within a word is subject to how a computer and user interpret it. For example, you may choose to use the Sign-Extend 15 or Post-Set '~~' operator in a Spin expression to convert a word value that you interpret as "signed" (-32,768 to +32,767) to a signed long value.