3.3 Instruction Types

Data movement instructions

	The different instruction types give the machine architecture more power. The following subsections explain
	the different possible instruction categories (Mostafa Abd-El-Barr, Hesham El-Rewini, (2004)).
	These instructions move the data among CPU registers and main memory. Table 3.1 shows the common data
	transfer instructions.

Data movement instructions	Meaning
MOVE	Move data from a given source (a register or a memory) to a given destination
LOAD	Load data from memory to a register
STORE	Store data into memory from a register
PUSH	Store data from a register to stack
POP	Retrieve data from stack into a register

Table 3.1: Data movement instructions (Mostafa Abd-El-Barr, Hesham El-Rewini, (2004)).

3.3 Instruction Types

Arithmetic and logical instructions

	Arithmetic and logical instructions perform arithmetic and logical operation on data in registers or main
	memory.
	Table 3.2 lists the arithmetic and Table 3.3 lists the logical instructions.

Arithmetic instructions	Meaning
ADD	Perform the arithmetic sum of two operands
SUBTRACT	Perform the arithmetic difference of two operands
MULTIPLY	Perform the product of two operands
DIVIDE	Perform the division of two operands
INCREMENT	Add one to the contents of a register
DECREMENT	Subtract one from the contents of a register

Table 3.2: Arithmetic instructions (Mostafa Abd-El-Barr, Hesham El-Rewini, (2004)).

3.3 Instruction Types

Logic instructions	Meaning
AND	Perform the logic AND of two operands
OR	Perform the logic OR of two operands
XOR	Perform the logic XOR of two operands
NOT	Perform the complement of an operand
COMPARE	Perform logical comparison of two operands and set flag accordingly
SHIFT	Perform logical shift (right or left) of the content of a register
ROTATE	Perform logical shift (right or left) with wraparound of the content of a register

Table 3.3: Logic instructions (Mostafa Abd-El-Barr, Hesham El-Rewini, (2004)).

3.3 Instruction Types

Control instructions

	Control (sequencing) instructions are used to change the instructions execution sequence by changing the
	program counter register contents.
	This type of instructions has the following categories: unconditional jump, conditional jump and call subroutine.
	The unconditional jump changes the execution sequence to a new address which holds the next instruction
	to be executed.
	The unconditional jump changes the PC contents to this new address.
	The conditional jump will perform the jump based on the condition of the flag bits.
	Table 3.4 has some flag examples.
	The flags may change based on the result of the execution of every instruction.

3.3 Instruction Types

Flag name	Meaning
Negative(N)	Set to 1 if the result of the most recent operation is negative, it is 0 otherwise
Zero(Z)	Set to 1 if the result of the most recent operation is 0, it is 0 otherwise
Overflow(V)	Set to 1 if the result of the most recent operation causes an overflow, it is 0 otherwise
Carry(C)	Set to 1 if the most recent operation results in a carry, it is 0 otherwise

Table 3.4: Examples of conditional flags (Mostafa Abd-El-Barr, Hesham El-Rewini, (2004)).

	The third type is calling a subroutine which causes the execution sequence to jump to the first instruction of
	this subroutine.

3.3 Instruction Types

Input/output instructions

	Input/output instructions are used to perform data transfer from/to peripheral devices.
	The INPUT instruction is used to transfer data from the input device to the processor.
	The OUTPUT instruction is used to transfer data from the processor to the output device.