8086 Assembly Language Programming

8086 Programming in Assembly Language

• The 8086 processor uses a variety of programming languages, including machine language, assembly language, and high-level languages.
• Machine language uses binary codes to represent instructions the microprocessor executes.
• Assembly language utilizes mnemonics (short, symbolic representations) for instructions.
• Programs in assembly language require translation to machine language (using an assembler).
• High-level languages are more English-like and use statements that often represent many machine code instructions.

Programmer's View of the Microcomputer

• The programmer views the microcomputer as a processor interacting with memory and input/output (I/O) devices via a bus interface.
• Memory components include RAM, SRAM, DRAM, ROM, PROM, EPROM, and EEPROM.
• I/O devices can be serial (e.g., serial port), parallel (e.g., parallel port), or others (e.g., keypad, display, hard disk).

Addressing Modes

• Addressing modes describe how operands are accessed and used in instructions.
• The effective address computation depends on the operands.
• Instructions can be categorized into sequential control flow instructions and control transfer instructions.
• Sequential instructions execute in sequence, while control transfer instructions alter the execution flow to a new part of the program.
• Different addressing modes exist for sequential and control-transfer instructions including immediate, direct, register, register indirect, indexed, register relative, and relative based indexed, along with addressing in intersegment and intrasegment instructions.

Instruction Set Overview

• 8086 instructions are categorized into six main types.
• Data transfer instructions move data between registers/memory locations and I/O ports.
• Arithmetic instructions perform calculations (add, subtract, multiply, divide, etc.).
• Bit manipulation instructions modify individual bits within data.
• String instructions handle strings of data in memory.
• Program execution transfer instructions control the flow of execution (jumps, calls, returns).
• Processor control instructions manage processor state (flags, halt, wait).

Assembler Directives

• Directives instruct the assembler how to process the program, not executed directly.
• Examples include ASSUME, specifying segment associations, DB (define byte), allocating memory, EQU assigning symbolic names to values, END to mark the program's end, processor directives such as EVEN, EXTRN, GLOBAL, INCLUDE, LENGTH, OFFSET, ORG and NAME.

Program Examples

• Examples illustrate how to use different instructions and directives to write programs that perform specific tasks, like adding numbers, processing strings and making arithmetic calculations by converting temperatures.