Undefined values: Difference between revisions
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=={{header|Z80 Assembly}}==
Nothing is truly "undefined" since any operation will return some 8-bit or 16-bit number. It's more of a question of "does this value mean anything at all." There are actions that will result in "undefined" (read: inconsistent) behavior:
* Reading from the <code>R</code> register (returns some value that relates to dynamic memory refresh)
* Reading from uninitialized memory (returns whatever happens to be there)
* Using <code>IN</code> commands on a port that isn't connected to the CPU, or reading from a write-only port
{{omit from|6502 Assembly}}
{{omit from|68000 Assembly}}
{{omit from|8080 Assembly}}
{{omit from|8086 Assembly}}
{{omit from|ARM Assembly}}
{{omit from|MIPS Assembly}}
{{omit from|X86 Assembly}}
{{omit from|Z80 Assembly}}
{{omit from|GUISS}}
{{omit from|ACL2}}
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