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
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.
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.
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.
Clear Direction flag. SI and DI will be incremented by chain instructions: CMPSB, CMPSW, LODSB, LODSW, MOVSB, MOVSW, STOSB, STOSW.
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.
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.
#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():
increment and decrement operations ie INC and DEC
The debug flag in the 8086/8088 microprocessor causes one instruction to be executed, followed immediately by a debug interrupt. The flag then gets turned off, so you get get nested debug interrupts. This is used by a debugger program to single step a process that it is debugging (the debugee, so to speak).
Flag pole you can pull down on the string and the flag will raise up
Clear direction flag (CLD) means that index registers will be incremented when looping through a string. Opposite of STD (set direction flag), which means the index registers of the string will be decremented when looping.