main memory with an indication of which process is assigned to each region

Main memory with an indication of which process is

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main memory with an indication of which process is assigned to each region Similar references will appear in I/O and file tables When processes communicate with one another, the process identifier informs the OS of the destination of a particular communication When processes are allowed to create other processes, identifiers indicate the parent and descendents of each process 36 33 34 35 36
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2/12/2020 10 • Contains condition codes plus other status information EFLAGS register is an example of a PSW used by any OS running on an x86 processor Program status word (PSW) • User-visible registers Control and status registers • Stack pointers Consists of the contents of processor registers 37 Figure 3.12 x86 EFLAGS Register X ID = Identification flag X VIP = Virtual interrupt pending X VIF = Virtual interrupt flag X AC = Alignment check X VM = Virtual 8086 mode X RF = Resume flag X NT = Nested task flag X IOPL = I/O privilege level S OF = Overflow flag C DF = Direction flag X IF = Interrupt enable flag X TF = Trap flag S SF = Sign flag S ZF = Zero flag S AF = Auxiliary carry flag S PF = Parity flag S CF = Carry flag 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 0 0 0 0 0 0 0 0 0 I D V I P V I F A C V M R F 0 N T I O P L O F D F I F T F S F Z F 0 A F 0 P F 1 C F 0 S Indicates a Status Flag C Indicates a Control Flag X Indicates a System Flag Shaded bits are reserved 38 Table 3.6 x86 EFLAGS Register Bits Status Flags (condition codes) AF (Auxiliary carry flag) Represents carrying or borrowing between half-bytes of an 8-bit arithmetic or logic operation using the AL register. CF (Carry flag) Indicates carrying out or borrowing into the leftmost bit position following an arithmetic operation. Also modified by some of the shift and rotate operations. OF (Overflow flag) Indicates an arithmetic overflow after an addition or subtraction. PF (Parity flag) Parity of the result of an arithmetic or logic operation. 1 indicates even parity; 0 indicates odd parity. SF (Sign flag) Indicates the sign of the result of an arithmetic or logic operation. ZF (Zero flag) Indicates that the result of an arithmetic or logic operation is 0. Control Flag DF (Direction flag) Determines whether string processing instructions increment or decrement the 16-bit half-registers SI and DI (for 16-bit operations) or the 32-bit registers ESI and EDI (for 32-bit operations). System Flags (should not be modified by application programs) AC (Alignment check) Set if a word or doubleword is addressed on a nonword or nondoubleword boundary. ID (Identification flag) If this bit can be set and cleared, this processor supports the CPUID instruction. This instruction provides information about the vendor, family, and model. RF (Resume flag) Allows the programmer to disable debug exceptions so that the instruction can be restarted after a debug exception without immediately causing another debug exception.
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