What are the flag bits in the control flag register?
The flag bits are changed to 0 or 1 depending upon the value of result after arithmetic or logical operations. 8086 has 16-bit flag register, and there are 9 valid flag bits….Status Flags.
| Flag Bit | Function |
|---|---|
| O | The overflow flag is set to 1 when the result of a signed operation is too large to fit. |
What is 32 bit register?
Data Registers Four 32-bit data registers are used for arithmetic, logical, and other operations. These 32-bit registers can be used in three ways − As complete 32-bit data registers: EAX, EBX, ECX, EDX. Lower halves of the 32-bit registers can be used as four 16-bit data registers: AX, BX, CX and DX.
What is the function of SI and DI register?
These registers are usually used to process arrays or strings. SI is called source index and DI is destination index. As the name follows, SI is always pointed to the source array and DI is always pointed to the destination. This is usually used to move a block of data, such as records (or structures) and arrays.
Which flag of 80386 in flag register controls string operations?
The control flag DF of the EFLAGS register controls string instructions. DF (Direction Flag, bit 10) Setting DF causes string instructions to auto-decrement; that is, to process strings from high addresses to low addresses.
Which flag is not in 80386?
The Intel 80386, part 3: Flags and condition codes
| Flag | Clear/Set | Notes |
|---|---|---|
| ZF | nz/zr | |
| AF | na/ac | Not used by C code |
| PF | pe/po | Not used by C code |
| CF | nc/cy |
How do you set a flag to one direction?
Set Direction Flag (std)
- Operation. 1 -> DF.
- Description. Sets the direction flag to 1, causing all subsequent string operations to decrement the index registers, (E)SI and/or (E)DI, used during the operation.
- Example. Set the direction flag: std.