Data Manipulation Instructions in Computer Organization

Data Manipulation Instructions Data manipulation instructions perform operations on data and provide computational capabilities for the computer. The data manipulation instructions in a typical computer are usually divided into three basic types as follows.

1. Arithmetic instructions
2. Logical and bit manipulation instructions
3. Shift instructions

Let’s discuss them one by one.

1. Arithmetic instructions: The four basic operations are addition, subtraction, multiplication, and division. Most computers provide instructions for all four operations. Typical Arithmetic Instructions –

Name	Mnemonic	Example	Explanation
Increment	INC	INC B	It will increment the register B by 1    B<-B+1
Decrement	DEC	DEC B	It will decrement the register B by 1   B<-B-1
Add	ADD	ADD B	It will add contents of register B to the contents of the  accumulator  and store the result in the accumulator   AC<-AC+B
Subtract	SUB	SUB B	It will subtract the contents of register B from the contents of the  accumulator  and store the result in the accumulator AC<-AC-B
Multiply	MUL	MUL B	It will multiply the contents of register B with the contents of the  accumulator and store the result in the accumulator AC<-AC*B
Divide	DIV	DIV B	It will divide the contents of register B with the contents of the  accumulator and store the quotient in the accumulator AC<-AC/B
Add with carry	ADDC	ADDC B	It will add the contents of register B and the carry flag with the contents of the accumulator and store the result in the  accumulator AC<-AC+B+Carry flag
Subtract with borrow	SUBB	SUBB B	It will subtract the contents of register B and the carry flag from  the contents of the accumulator and store the result in the  accumulator AC<-AC-B-Carry flag
Negate(2’s complement)	NEG	NEG  B	It will negate a value by finding 2’s complement of its single operand. This means simply operand by -1. B<-B’+1

1. Logical and Bit Manipulation Instructions: Logical instructions perform binary operations on strings of bits stored in registers. They are helpful for manipulating individual bits or a group of bits. Typical Logical and Bit Manipulation Instructions –

Name	Mnemonic	Example	Explanation
Clear	CLR	CLR	It will set the accumulator to 0  AC<-0
Complement	COM	COM A	It will complement the accumulator AC<-(AC)’
AND	AND	AND B	It will AND the contents of register B with the contents of accumulator and store  it in the accumulator AC<-AC AND B
OR	OR	OR B	It will OR the contents of register B with the contents of accumulator and store it in the accumulator AC<-AC OR B
Exclusive-OR	XOR	XOR B	It will XOR the contents of register B with the contents of the accumulator and  store it in the accumulator AC<-AC XOR B
Clear carry	CLRC	CLRC	It will set the carry flag to 0 Carry flag<-0
Set carry	SETC	SETC	It will set the carry flag to 1 Carry flag<-1
Complement carry	COMC	COMC	It will complement the carry flag Carry flag<- (Carry flag)’
Enable interrupt	EI	EI	It will enable the interrupt
Disable interrupt	DI	DI	It will disable the interrupt

1. Shift Instructions: Shifts are operations in which the bits of a word are moved to the left or right. Shift instructions may specify either logical shifts, arithmetic shifts, or rotate-type operations. Typical Shift Instructions –

Name	Mnemonic
Logical shift right	SHR
Logical shift left	SHL
Arithmetic shift right	SHRA
Arithmetic shift left	SHLA
Rotate right	ROR
Rotate left	ROL
Rotate right through carry	RORC
Rotate left through carry	ROLC

For Shift Instructions, refer to this Reference for Shift Instructions