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What are assembly language instructions?
Instructions (statements) in assembly language are generally very simple, unlike those in high-level languages. Generally, a mnemonic is a symbolic name for a single executable machine language instruction (an opcode), and there is at least one opcode mnemonic defined for each machine language instruction.
What is AH and AL in assembly language?
The least significant byte of AX can be used as a single 8-bit register called AL, while the most significant byte of AX can be used as a single 8-bit register called AH. These names refer to the same physical register. When referring to registers in assembly language, the names are not case-sensitive.
What is Lea Assembly?
lea — Load effective address. The lea instruction places the address specified by its first operand into the register specified by its second operand. Note, the contents of the memory location are not loaded, only the effective address is computed and placed into the register.
What are the four different types of instructions assembly?
Instruction types include arithmetic, logical, data transfer, and flow control. Instruction modes include kernel and user instructions.
What is xor used for in Assembly?
The XOR instruction performs a bit wise Exclusive OR operation between corresponding bits in the two operands and places the result in the first operand. reg, mem, and immed can be 8, 16, or 32 bits. The XOR instruction can be used to reverse selected bits in an operand while preserving the remaining bits.
What is xor EAX EAX?
xor eax, eax is a faster way of setting eax to zero. This is happening because you’re returning zero. The in instruction is doing stuff with I/O ports. Basically reading a word of data from the port specified dx in and storing it in al .
How are read and write operations performed in memory?
Data input lines provide the information to be stored into the memory, Data output lines carry the information out from the memory. The control lines Read and write specifies the direction of transfer of data. Basically, in the memory organization, there are memory locations indexing from 0 to where l is the address buses.
Where does the read and write in memory take place?
In the above diagram initially, MDR can contain any garbage value and MAR is containing 2003 memory address. After the execution of read instruction, the data of memory location 2003 will be read and the MDR will get updated by the value of the 2003 memory location (3D).
Which is the address register in the memory?
Memory Address Register (MAR) is the address register which is used to store the address of the memory location where the operation is being performed. Memory Data Register (MDR) is the data register which is used to store the data on which the operation is being performed.
How is information stored in a memory unit?
A memory unit stores binary information in groups of bits called words. Data input lines provide the information to be stored into the memory, Data output lines carry the information out from the memory. The control lines Read and write specifies the direction of transfer of data.