Intel 80C196NU 用户手册
8XC196NP, 80C196NU USER’S MANUAL
4-2
Table 4-2 lists the equivalent operand-type names for both C programming and assembly lan-
guage.
guage.
4.1.1
BIT Operands
A BIT is a single-bit variable that can have the Boolean values, “true” and “false.” The architec-
ture requires that BITs be addressed as components of BYTEs or WORDs. It does not support the
direct addressing of BITs.
ture requires that BITs be addressed as components of BYTEs or WORDs. It does not support the
direct addressing of BITs.
4.1.2
BYTE Operands
A BYTE is an unsigned, 8-bit variable that can take on values from 0 through 255 (2
8
–1). Arith-
metic and relational operators can be applied to BYTE operands, but the result must be interpret-
ed in modulo 256 arithmetic. Logical operations on BYTEs are applied bitwise. Bits within
BYTEs are labeled from 0 to 7; bit 0 is the least-significant bit. There are no alignment restric-
tions for BYTEs, so they may be placed anywhere in the address space.
ed in modulo 256 arithmetic. Logical operations on BYTEs are applied bitwise. Bits within
BYTEs are labeled from 0 to 7; bit 0 is the least-significant bit. There are no alignment restric-
tions for BYTEs, so they may be placed anywhere in the address space.
4.1.3
SHORT-INTEGER Operands
A SHORT-INTEGER is an 8-bit, signed variable that can take on values from –128 (–2
7
) through
+127 (+2
7
–1). Arithmetic operations that generate results outside the range of a SHORT-INTE-
GER set the overflow flags in the processor status word (PSW). The numeric result is the same
as the result of the equivalent operation on BYTE variables. There are no alignment restrictions
on SHORT-INTEGERs, so they may be placed anywhere in the address space.
as the result of the equivalent operation on BYTE variables. There are no alignment restrictions
on SHORT-INTEGERs, so they may be placed anywhere in the address space.
Table 4-2. Equivalent Operand Types for Assembly and C Programming Languages
Operand Types
Assembly Language Equivalent
C Programming Language Equivalent
BYTE
BYTE
unsigned char
SHORT-INTEGER
BYTE
char
WORD
WORD
unsigned int
INTEGER
WORD
int
DOUBLE-WORD
LONG
unsigned long
LONG-INTEGER
LONG
long
QUAD-WORD
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