System information

3.5.6 Control Instructions
The four remaining instructions, categorized as control instructions, are the following:
-HLT halts the 8080 processor.
-DI disables the interrupt system.
-EI enables the interrupt system.
-NOP means no operation.
3.6 Error Messages
When errors occur within the assembly-language program, they are listed as singlecharacter flags
in the leftmost position of the source listing. The line in error is also echoed at the console so that
the source listing need not be examined to determine if errors are present. The error codes are
listed in the following table.
Table 3-9. Error Codes
Error Code Meaning
D Data error: element in data statement cannot be placed in the specified data area.
E Expression error: expression is ill-formed and cannot be computed at assembly time.
L Label error: label cannot appear in this context; might be duplicate label.
N Not implemented: features that will appear in future ASM versions. For example, macros
are recognized, but flagged in this version.
O Overflow: expression is too complicated (too many pending operators) to be computed
and should be simplified.
P Phase error: label does not have the same value on two subsequent passes through the
program.
3.5 Operation Codes CP/M Operating System Manual
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