Why DAA Instruction Is To Be Written Just After Add Instruction?

The DAA (Decimal Adjust after Addition) instruction

allows addition of numbers represented in 8-bit packed BCD code

. It is used immediately after normal addition instruction operating on BCD codes. This instruction assumes the AL register as the source and the destination, and hence it requires no operand.

What is the purpose of DAA instruction?

The DAA instruction is only useful when it follows an ADD instruction that

adds (binary addition) two 2-digit, packed BCD values and stores a byte result in the AL register

. The DAA instruction then adjusts the contents of the AL register to contain the correct 2-digit, packed BCD result.

Why DAA instruction is to be written just after add sub instructions?

The DAA (Decimal Adjust after Addition) instruction

allows addition of numbers represented in 8-bit packed BCD code

. It is used immediately after normal addition instruction operating on BCD codes. This instruction assumes the AL register as the source and the destination, and hence it requires no operand.

What happens when DAA instructions is executed?

The DAA instruction then

adjusts the contents of the AL register to contain the correct 2-digit, packed BCD result

. If a decimal carry is detected, the CF and AF flags are set accordingly. This instruction executes as described above in compatibility mode and legacy mode.

Which addressing mode is used in instruction DAA?

Which addressing mode is used in instruction DAA?

Immediate Addressing Mode

: In the type of addressing mode, the operand is available directly in the instruction itself. If the operand data involved is of 8-bits then the instruction is of two bytes.

What is the full form of DAA?

What is BCD number?

In computing and electronic systems, binary-coded decimal (BCD) is

a class of binary encodings of decimal numbers where each digit is represented by a fixed number of bits

, usually four or eight. Sometimes, special bit patterns are used for a sign or other indications (e.g. error or overflow).

Under what circumstances does DAA instruction set the carry flag?

DAA must always follow the addition of two pairs of packed decimal numbers (one digit in each half-byte) to obtain a pair of valid packed decimal digits as results. The carry flag is set

if carry was needed

.

How many Byte instruction is daa?

Summary − So this instruction DAA requires

1-Byte

, 1-Machine Cycle (Opcode Fetch) and 4 T-States for execution as shown in the timing diagram.

How many bits is 8086?

1) The 8086 is a

16-bit

microprocessor. The term “16-bit” means that its arithmetic logic unit, internal registers and most of its instructions are designed to work with 16-bit binary words. 2) The 8086 has a 16-bit data bus, so it can read data from or write data to memory and ports either 16 bits or 8 bits at a time.

When a word operand is multiplied with ax the result is stored in which register?

The multiplicand should be in

the AX register

, and the multiplier is a word in memory or another register. For example, for an instruction like MUL DX, you must store the multiplier in DX and the multiplicand in AX. The resultant product is a doubleword, which will need two registers.

Which instruction affects maximum number of flags?

XRA

affects the maximum number of flags as it affects all the flags.

Which of the following is 3 Byte instruction?

Three-byte instruction is the type of instruction in which the first 8 bits indicates the

opcode

and the next two bytes specify the 16-bit address. The low-order address is represented in second byte and the high-order address is represented in the third byte.

What is the immediate addressing mode?

Immediate—Immediate addressing is not really an addressing mode into memory; rather, it is

an instruction format that directly includes the data to be acted on as part of the instruction

. This form of operand access simplifies the instruction execution cycle since no additional fetches are required.

Which register pair is used to indicate memory?

H and L register pair

is used to act as memory pointer and it holds 16 bit address of memory location.

What is direct addressing mode?

Direct addressing mode means that

the value for a given instruction in assembly programming is pointed to by a given value

. This means the value is variable, based on what is stored in memory at a given address.