The Intel 8086 processor is a 16-bit microprocessor that debuted in 1978. It was one of the first processors to introduce the x86 architecture, which later became popular and forms the basis of many modern processors. The 8086 is an example of a CISC (Complex Instruction Set Computer) processor, which has a rich instruction set that allows complex operations to be performed in a single cycle.

The 8086 processor has a number of features that have defined its architecture:

* Registers : The processor has 14 main registers, including general purpose registers (AX, BX, CX, DX, SI, DI, BP, SP), segment registers (CS, DS, SS, ES) and an instruction pointer (IP) register.

* Memory addressing : The processor uses segmented memory addressing, which means that all 8086 memory is divided into segments (up to 1 MB of memory). Memory addresses are created by a 16-bit segment register and a 16-bit offset register.

* Duty cycle : The 8086 operates on the principle of clock cycles, in which it performs read, write and instruction execution operations.

The 8086 processor executes instructions in various modes:

* Real-mode : This is the mode in which the processor performs operations without memory virtualisation and without memory protection.

* Protection mode : This mode is more advanced and allows memory to be managed in a more secure way (although the 8086 processor did not support it directly, but in later versions, such as the 80286, this mode was introduced).

Below I present some examples of assembler language programs for the 8086 processor. These examples illustrate basic operations performed by the processor, such as register manipulation, port input/output and basic conditional jumps.

JMP main		;
 
	DB 90		;
	DB D8		;
	DB 24		;
	DB 48		;
 
main:
	MOV DL,02	; ustawienie DL na pierwszym adresie danych w RAM
			; Turn off all the traffic lights.
	MOV AL,0	; Copy 00000000 into the AL register.
	OUT 01		; Send AL to Port One (The traffic lights).
 
start:
	MOV AL,[DL]	; pobranie wartości spod adresu DL
	OUT 01		;		
	INC DL		;
	CMP DL,5	;
	JZ end		;
	JMP start	; Jump back to the start.
end:
	END		; Program ends.

* The programme loads data from memory and sends it to the port (simulating traffic light control).

* Values are stored in memory and the processor sends them to the corresponding port using an `OUT` instruction.

* The program stops when the number of data sent reaches 5.

Start:
	MOV	AL,B6	; 1111 1010
	OUT	02	; Send the data in AL to Port 02
 
	MOV	AL,0B	; 0000 0000
	OUT	02	; Send the data in AL to Port 02
 
	JMP	Start
 
	END

* The program sets the value `B6` in the AL register and then sends it to port 02.

* It then sets the value `0B` in the AL register and sends it to port 02 again.

* The program repeats these operations indefinitely.

start:
 
	IN	03	; Input from Port 03
	AND	AL,1	; Mask off left seven bits
	JZ	Cold	; If the result is zero, turn the heater on
	JMP	Hot	;
 
Cold:
	MOV	AL,80	; Code to turn the heater on
	OUT	03	; Send code to the heater
	JMP start	;
Hot:
	MOV	AL,0	; Code to turn the heater off
	OUT	03	; Send code to the heater
	JMP start	;
 
	JMP start	;
 
END

* The program reads data from port 03 and checks that the youngest bit is set to 0 (which may mean that the temperature is too low).

* Depending on the result, the program turns the heater on or off by sending the appropriate code to port 03.

JMP Start
 
	DB	1		;
	DB 	"I AM KACPER" 	; 
	DB 	0		;
 
 
Start:
 
	MOV 	BL,02 		; 02 adres początku danych
	MOV 	CL,C0 		; C0 adres początku danych wyświetlacza
 
Rep1:
 
	MOV 	AL,[BL]		; z komórki w pamięci o adresie BL pobieram wartość do rejestru AL
	MOV 	DL,[BL]		; z komórki w pamięci o adresie DL pobieram wartość do rejestru AL
	PUSH 	AL		;
	MOV 	[CL],DL		; z rejestru DL zapisuje wartość w pamięci o adresie CL
	CMP 	AL,0 		; czy ostatni element ? 5 to ostatni adres komórki w której są dane 
	JZ 	continue 	; jesli tak, to skocz do start, zaczynamy od poczatku
	INC 	BL 		; jesli nie, to wez kolejny element
	INC 	CL		; zwiększam adres danych wyświetlacza
	JMP 	Rep1 		; skok na poczatek
 
continue:
 
	MOV 	CL,D0 		; C0 adres początku danych wyświetlacza
 
Rep2:
 
	POP 	AL		;
	MOV 	[CL],AL		; z rejestru DL zapisuje wartość w pamięci o adresie CL
	CMP 	AL,1 		; czy ostatni element ? 5 to ostatni adres komórki w której są dane 
	JZ 	end 		; jesli tak, to skocz do start, zaczynamy od poczatku
	INC 	BL 		; jesli nie, to wez kolejny element
	INC 	CL		; zwiększam adres danych wyświetlacza
	JMP 	Rep2 		; skok na poczatek
 
end:
	end

* The programme displays the words „I AM KACPER” on the screen.

* Moves data from one memory cell to another using registers and memory manipulation instructions.

The SMZ32V50 simulator was used to execute the above programs. It is a tool that enables the emulation of the operation of the 8086 processor, allowing the testing and debugging of programs in assembler. This simulator can emulate the operation of input/output ports and memory, making it an ideal tool for learning and testing code for this type of processor.

smz32v50.exe

The 8086 processor was a pioneer in many aspects of computer architecture. Thanks to its simplicity and flexibility, programming in the assembler of this processor is still a valuable learning resource for those who want to understand the basics of computers. The examples of the above programs show how to use the processor's instructions to perform a variety of operations such as register manipulation, interaction with input/output ports and simple control structures.