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Questions and Answers

What are the two types of variables supported by the compiler?

BYTE and WORD (correct)

INTEGER and FLOAT

BOOLEAN and NULL

STRING and CHAR

What is the purpose of a register?

To keep a number (variable)

What is the primary function of the MOV instruction?

To compare two operands

To copy the second operand to the first operand (correct)

To add two operands

To subtract two operands

What is the significance of the ORG directive?

It instructs the compiler how to handle the source code and calculate the correct address for all variables. Signup and view all the answers

The term "segment" refers to the value stored in a general-purpose register.

False Signup and view all the answers

What is the main purpose of the stack?

Keeping temporary data, return addresses, and flag registers for procedures and interrupts. Signup and view all the answers

The JMP instruction is a conditional jump instruction.

False Signup and view all the answers

What is the purpose of the INT instruction?

To execute a software interrupt Signup and view all the answers

What is the purpose of procedures in assembly language?

To make the code more structured and easier to understand Signup and view all the answers

What is the key difference between a macro and a procedure?

Macros are replaced with actual instructions during the compilation while procedures are blocks of code stored in memory and executed when called. Signup and view all the answers

What is the purpose of using a data table to control external devices?

To store values representing specific states or configurations for the device. Signup and view all the answers

What are the advantages of booting from a floppy disk?

It allows you to keep the existing operating system untouched while making changes to the floppy drive and it's easier to modify its boot record. Signup and view all the answers

What is the purpose of the "#make_boot#" directive?

To create a bootable .com file Signup and view all the answers

What is the main function of the INT 13h instruction?

To read sectors from a floppy disk. Signup and view all the answers

What is the purpose of the "include 'emu8086.inc'" line in the code?

To include a library file with useful macros and procedures for simplifying common assembly tasks. Signup and view all the answers

What happens to all loop instructions when the address of the desired location is too far?

The assembler automatically generates reverse and long jump instructions. Signup and view all the answers

What is the main purpose of the LEA instruction?

To load the effective address of a variable into a register Signup and view all the answers

The CMP instruction is also used to subtract two operands, similar to the SUB instruction.

True Signup and view all the answers

What is the function of the "#fasm#" directive?

This directive indicates that the following code is written for a flat assembler, like FASM, which uses a different syntax and doesn't require the offset directive. Signup and view all the answers

Study Notes

8086 Assembler Tutorial for Beginners (Part 1)

This tutorial is for beginners unfamiliar with assembler.
Knowledge of another programming language (e.g., Basic, C/C++, Pascal) is helpful.
Understanding number representation (hexadecimal, binary) is recommended.

What is Assembly Language?

Assembly language is a low-level programming language.
Requires knowledge of computer structure.
A simple model includes a System Bus (yellow) connecting components.
The CPU is the computer's central processing unit.
Calculations occur inside the CPU.
RAM (Random Access Memory) is where programs are loaded.

Inside the CPU

The CPU contains general-purpose registers (e.g., AX, BX, CX, DX, SI, DI, BP, SP).
These are 16-bit registers, often divided into 8-bit parts (e.g., AX = AH + AL).
Segment registers (CS, DS, ES, SS) specify memory locations.
- CS: points to the segment containing the current program.
- DS: generally points to the segment where variables are defined.
- ES: extra segment register.
- SS: points to the segment containing the stack.
The Instruction Pointer (IP) points to currently executing instructions.
The flags register contains the state of the microprocessor.

Memory Access

Memory locations are accessed using these 4 general registers: BX, SI, DI, BP in combination using the addressing modes.
d8 - stays for 8-bit signed immediate displacement (e.g., 22, 55h, -1).
d16 - stays for 16-bit signed immediate displacement (e.g., 300, 5517h, -259).
Combining registers allows access to a wider range of memory addresses.
Segment and general purpose registers are needed to specify addresses.