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In the 8086 microprocessor, the Direction Flag (DF) is used for string manipulation instructions. It determines the direction in which string operations proceed: if DF is set (DF = 1), the operations are performed from high memory addresses to low (decrementing); if DF is clear (DF = 0), the operations proceed from low to high memory addresses (incrementing). This allows for flexibility in how strings are processed in memory.
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What is flag manipulation instructions?
flag manipulation instructions are which changes the flag conditions for example STC - set the carry flag STI - set the interrupt flag so interrupts will be enabled SATISH MN
What is the use of direction flag and Trace flag in 8086?
The direction flag (DF) controls the direction of repeated string instructions. The trap flag (TF) executes one instruction and then executes a debug (INT 1) instruction so that a debugger can single step through a program.
What type of flags in 8086 and 8088 microprocessor and their uses.?
There are nine flags in the 8086/8088.SF - Sign Flag - The result is negativeZF - Zero Flag - The result is zeroAF - Auxillary Carry Flag - A BCD carry occurredPF - Parity Flag - Indicates the oddness or evenness of the number of bitsCF - Carry Flag - An unsigned carry occurredOF - Overflow Flag - A signed overflow/carry occurredDF - Direction Flag - Controls the direction of repeated string operationsIF - Interrupt Flag - Enables or disables interruptsTF - Trace Flag - Controls the debug single step interruptIn general, most of these flags are set as a result of some arithmetic or logical instruction and can be tested using the conditional branch instructions. Exceptions are DF, which controls the directionality of repeated string operations, IF, which controls interrupts, and TF, which controls debugging.
what type of flags in 8086 and 8088 microprocessor and their uses?
There are nine flags in the 8086/8088.SF - Sign Flag - The result is negativeZF - Zero Flag - The result is zeroAF - Auxillary Carry Flag - A BCD carry occurredPF - Parity Flag - Indicates the oddness or evenness of the number of bitsCF - Carry Flag - An unsigned carry occurredOF - Overflow Flag - A signed overflow/carry occurredDF - Direction Flag - Controls the direction of repeated string operationsIF - Interrupt Flag - Enables or disables interruptsTF - Trace Flag - Controls the debug single step interruptIn general, most of these flags are set as a result of some arithmetic or logical instruction and can be tested using the conditional branch instructions. Exceptions are DF, which controls the directionality of repeated string operations, IF, which controls interrupts, and TF, which controls debugging.
What is CLD in 8086?
Clear Direction flag. SI and DI will be incremented by chain instructions: CMPSB, CMPSW, LODSB, LODSW, MOVSB, MOVSW, STOSB, STOSW.
Enlist the types of flags in 8086?
The 8086 microprocessor has several types of flags, categorized into two main groups: status flags and control flags. Status flags include the Zero Flag (ZF), Sign Flag (SF), Parity Flag (PF), Carry Flag (CF), and Overflow Flag (OF), which indicate the outcome of arithmetic and logical operations. Control flags include the Direction Flag (DF), which determines the direction of string operations, and the Interrupt Flag (IF), which enables or disables interrupts. Additionally, there is a Trap Flag (TF) used for single-step debugging.
When does the overflow flag in 8086 set?
In the 8086/8088, the overflow flag is set when the result of an arithmetic instruction exceeds the bounds of the signed representation of a number. This is not the same as the carry flag, which is used for the unsigned representation. Both flags get set as needed. You decide which one to pay attention to.
Show bitwise psw of 8085 and 8086 and explain the function of each flag with an example?
The Program Status Word (PSW) for the 8085 and 8086 microprocessors consists of various flags that indicate the status of operations. In the 8085, the flags include the Sign Flag (S), Zero Flag (Z), Auxiliary Carry Flag (AC), Parity Flag (P), and Carry Flag (CY). For example, if an operation results in a negative value, the Sign Flag is set, while if the result is zero, the Zero Flag is set. In 8086, the PSW includes similar flags but adds the Overflow Flag (OF), which indicates an overflow in signed arithmetic operations.
Which bit of flag register can be changed directly in assembly language?
In assembly language, the Zero Flag (ZF) can be directly affected by certain instructions, such as comparisons (e.g., CMP) and arithmetic operations. Other flags, like the Carry Flag (CF) or Sign Flag (SF), are typically modified by specific instructions and cannot be set or cleared directly. The Control Flag bits, such as the Interrupt Flag (IF), can be manipulated using specific instructions like CLI and STI. Overall, while some flags can be influenced indirectly through operations, direct manipulation is limited.
What are the functions of execution unit in 8086 Intel?
Basically the function of execution unit in 8086 is to perform all arithmetic and logic operations.It tells the Bus Interface unit(BIU) where to fetch instructions and data from.It has 4 components:Control circuitry,ALU,Flag registers and general purpose registers. 1.control circuits-it directs all the internal operations. 2.ALU-performs all logic operations. 3.general purpose registers-used to store data during execution. 4.flag registers-it has a 16bit flag register containing 9 flags that are set for certain conditions during any operation.Ex.carry flag(whenever there is a carry). It also has a decoder to decode the fetched instructions.
How is parity flag affected with the or instruction in 8086 microprocessor?
In the 8086 microprocessor, the parity flag (PF) is affected by the OR instruction based on the result of the operation. The parity flag is set if the number of set bits (1s) in the result is even; it is cleared if the number of set bits is odd. Therefore, after executing an OR instruction, the parity flag reflects the parity of the result of the logical OR operation performed on the operands.
How do you write a program to check the string of a given grammar?
#include<stdio.h> #include<conio.h> #include<string.h> void main() { char string[50]; int flag,count=o; clrscr(); printf("The grammar is: S->aS, S->Sb, S->ab\n"); printf("Enter the string to be checked:\n"); gets(string); if(string[0]=='a') { flag=0; for(count=1;string[count-1]!='\0';count++) { if(string[count=='b']) { flag=1; continue; } else if((flag==1)&&(string[count]=='a')) { printf("The string does not belong to the specified grammar"); break; } else if(string[count=='a']) continue; else if(flag==1)&&(string[count]='\0')) { printf("The string accepted"); break; } else { printf("String not accepted"); } getch():
