CLD: clear direction flag so that string pointers auto increment after each string operation. STD: std is used to set the direction flag to a 1 so that SI and/or DI will automatically be decremented to point to the next string element when one of the string instruction executes.
What does CLD mean in assembly language?
Clear Direction Flag (cld) (IA-32 Assembly Language Reference Manual)
What happens when CLD is executed 8086?
CLD Instruction :
This instruction is used to reset the direction flag to zero , so that SI and/or DI can be incremented automatically after execution of string instructions. CLD does not affect any other flag.
What happens when we execute CLD in 8086 * 1 point clear carry flag clear direction flag set Diection flag clear interrupt flag?
CLD — Clear Direction Flag CLD clears the direction flag. No other flags or registers are affected. After CLD is executed, string operations will increment the index registers (SI and/or DI) that they use .
What is BT instruction?
From Wikipedia, the free encyclopedia. The BT x86 assembly language instruction stands for Bit Test and was added to the x86 instruction set with the 80386 processor. BT copies a bit from a given register to the carry flag. Example: copy the third least significant bit from EAX to the carry flag.
What is Movsb Assembly?
The MOVSB ( move string, byte ) instruction fetches the byte at address SI, stores it at address DI and then increments or decrements the SI and DI registers by one.
What is Lodsb Assembly?
The size of the source and destination operands is selected with the mnemonic: LODSB ( byte loaded into register AL ), LODSW (word loaded into AX), or LODSD (doubleword loaded into EAX).
What is the difference between 8085 and 8086 microprocessor?
| Property 8085 Microprocessor 8086 Microprocessor | Data Bus Size 8-Bit 16-Bit | Address Bus Size 16-bit 20-bit | Clock Speed 3MHz Varies in range 5.8 – 10 MHz | Duty Cycle for clock 50% 33% |
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What are assembler directives in 8086?
Introduction: Assembler directives are the directions to the assembler which indicate how an operand or section of the program is to be processed . These are also called pseudo operations which are not executable by the microprocessor.
How many instructions are there in 8086?
Ans. There are 117 basic instructions in the instruction set of 8086.
What is the function of DF flag?
The direction flag is a flag that controls the left-to-right or right-to-left direction of string processing , stored in the FLAGS register on all x86-compatible CPUs. It is bit number 10.
What is the use of interrupt flag?
The Interrupt flag (IF) is a flag bit in the CPU’s FLAGS register, which determines whether or not the (CPU) will respond immediately to maskable hardware interrupts . If the flag is set to 1 maskable interrupts are enabled.
What is the function of trap flag?
A trap flag permits operation of a processor in single-step mode . If such a flag is available, debuggers can use it to step through the execution of a computer program.
What is bit assembly?
BIT (short for “BIT test”) is the mnemonic for a machine language instruction which tests specific bits in the contents of the address specified , and sets the zero, negative, and overflow flags accordingly, all without affecting the contents of the accumulator. ...
How does a bit test work?
Description. Selects the bit in a bit string (specified with the first operand, called the bit base) at the bit-position designated by the bit offset operand (second operand) and stores the value of the bit in the CF flag. ... The processor will ignore the high order bits if they are not zero.
What is the difference between shift and rotate instruction?
Shift and Rotate commands are used to convert a number to another form where some bits are shifted or rotated. Basic difference between “shift” and “rotate” is shift command makes “fall of” bits at the end of register whereas rotate command makes “Wrap around” at the end of the register.
