Introduction to Machine Language
DEBUG
A software that is classifies as debugger which is used for testing and debugging executable programs
Advantages
It is Free
It is universally available
It is simple to use
It requires relatively little memory
DEBUG COMMANDS
E (Enter)
-enable you to key in data or machine instruction into memory beginning at a specific location address.
E.g -E 0200
D (Display or Dump)
Displays the contents of a portion memory ni hex and ASCII forms starting with the given address
E.g. -D 0200
A (Assemble)
Allows you to create a program in mnemonic or symbolic code.
E.g. -A 0100
T (Trace)
Runs he program in single-step mode. It also displays the new values of the registers and the next instruction to be executed.
E.g -T
G (Go)
Runs the program as a whole in memory an displays the output
E.g. -G
U (Unassemble)
Lists all the instructions contained in the program beginning at the given address. You can also specify the last address location.
E.g. -U 0100
-U 0100 0109
N (Name)
Gives a name to your program, coded as N <path> <filename>
Extention nae is .COM
E.g. -N A:SAMPLE.COM
W (Write)
Saves the program onto disk storage
E.g. -W
BASIC ASSEMBLY INSTRUCTIONS USED IN DEBUG
MOV (Move Data)
Copies and transfers data between two registers, or between an immediate data to a register
Format: MOV <register>, <register>
MOV <register>, <immediate data>
Example: MOV AX, BX
MOV CX, 5083
MOV CL, DL
MOV BL, 33
ADD (Add Data)
Used to get the sum of two registers or a register and an immediate data, and stores the result to the left most register
Format: ADD <register>, <register>
ADD <register>, <immediate data>
Example: ADD CX, BX
ADD AX, 0308
ADD AL, BL
ADD DH, 85
MUL (Multiply Data)
It is used to get the product of a given register and AX register, and stores the result to AX register. If the product is greater than 16 bits, the overflow is stored in DX register.
Format: MUL <register>
Example: MUL CX
DIV (Divide Data)
Used to divide the value of a given register and AX register, stores the quotient to AX and the remainder to DX registers respectively
Format: DIV <register>
Example DIV BX
INC (Increment by One)
Used to increase the value of the register by one (1).
Format: INC register
Example: INC AX
INC CH
DEC (Decrement by One)
Opposite of INC, decreases the value of the register by one (1).
Format: DEC <register>
Example: DEC AX
DEC CH
LOOP (Loop Until Complete)
It controls the execution of a program segment in a specified number of times.
The CX register should contain a count value before starting the loop and automatically decrements by one (1)
If CX is not equal to zero (0), it transfers to its operand address which points to the start of the loop; otherwise it drops to the nest instruction.
Format: LOOP <offset address>
Example: LOOP 0108
CODING ASSEMBLY LANGUAGE IN TASM
Comment
Ignored by the assembler.
Can improve program’s readability and clarity
Begins with a semicolon (
Ways to include comment
Any statement whose first non-block character is a semicolon
Example:
; This program displays Hello, World!
At the end of an instruction
Example:
MOV AX, 8053H ;initializes the value of AX to 8053
Reserved Words
Words in which the assembler assigns a special meaning and it cannot be used as identifiers
Using reserved words for a wrong purpose causes the assembler to generate an error message
Categories of reserved words
Instructions
Statements that will be translated into machine language and executed by the computer.
Examples:
MOV ADD SUB
MUL DIV INC
DEC LOOP CMP
Directives
Statements that give information to the assembler
Sometimes called pseudo-ops
Examples:
TITLE DOSSEG .MODEL
.STACK .DATA .CODE
Rules in Constructing Valid identifier
It must use letters (A...Z, a…z), number (0…9) and/or special characters like underscore (_), question mark (?) and at sign (@).
It must always start with a letter
It must not use reserved words
It must not exceed to 31 character.
Examples of valid identifiers:
neym r2d2
num_1 msg8
Examples of invalid identifiers:
title num-1
4ever
Statement
May begin anywhere on the line
Each line can only contain one statement
Assembly is not case sensitive
Examples:
ADD AX, BX ; uses 2 operands
DEC CX ; uses
RET ; no operand
Most common directives
TITLE
It creates a title (up to 60 characters) of a source listing.
Format:
TITLE <TEXT>
Examples:
TITLE This program displays Kumusta, BUPC!
TITLE PROGRAM1.ASM
.MODEL
It specifies and initializes the memory model before defining any segment
Format:
.MODEL <memory-model>
Examples:
.MODEL TINY
.MODEL SMALL
.MODEL MEDIUM
.STACK
It defines the size of the attack. The default stack size is 1,024 bytes which you can overrule.
Format:
.STACK <size>
Example:
.STACK 0100h
.DATA
It defines and marks the beginning of data segment
Format:
.DATA
Example:
.DATA
.CODE
It defines and marks the code segment which consists of a set of instructions.
Format:
.CODE
Example:
.CODE
START:
Defines the start of program execution
Format:
START:
Examples:
START:
END
It is placed at the last line of the source code
Format:
END
Example:
END START
STRING
Used for descriptive data such as person’s name or simply a message.
It must end with dollar ($) symbol and defined in double quotation marks (“ “).
DB is the conventional format for defining string of any length.
Example:
neym db “Louis Vuitton$”
Numeric Constant
Used to define arithmetic values and memory address.
It is defined with a radix specifier such as d for decimal, b for binary and h for hexadecimal.
Example:
msg db “Bon jour, monsieur!”, 0Ah, 0Dh, “$”
msg db “Bon jour, monsieur!”, 10d, 13d, “$”
msg db “Bon jour, monsieur!”, 00001010b, 00001101b, “$”
Screen Processing
The monitor
A typical video screen has 80 columns numbered form 0 to 79 and 25 rows numbered from 0 to 24.
Clearing the screen in Assembly Approach
Interrupt 10h and function 06h handles the process of clearing the screen and scrolling
Clear all or part of display beginning at any screen location and ending at any higher-numbered location.
Sample code shows how to clear screen code in assembly
MOV AX, 0600h ; AH = 00h (scroll), AL, 00h (Full screen)
MOV BH, 07h ; 0 (BLACK BACKGROUND), 7 (WHITE TEXT COLOR)
MOV CX, 0000h ; CH = 00H (ROW), CL, 00H (COLUMN)
MOV DX, 184Fh ; DH = 18H (ROW), DL=4FH (COLUMN)
INT 10h ; CALL INTERRUPT SERVICE
SETTING THE CURSOR FUNCTION
Interrupt 10h is the BIOS operation for screen handling and function 02h tells the operation to set the cursor
Its position determines where the next character is to be displayed.
MOV AH, 02H ; REQUEST TO SET THE CURSOR POSITION
MOV BH, 00H ; PAGE NUMBER 0
MOV DH, 0AH ; ROW - 10 IN DECIMAL
MOV DL, 08H ; COLUMN = 8 IN DECIMAL
INT 10H
MAY CONTINUATION PA PO ITO, WAIT NYO LANG
Press thanks kung nakatulong,
Accepting Requests for Tutorial in any Programming Languages
DEBUG
A software that is classifies as debugger which is used for testing and debugging executable programs
Advantages
It is Free
It is universally available
It is simple to use
It requires relatively little memory
DEBUG COMMANDS
E (Enter)
-enable you to key in data or machine instruction into memory beginning at a specific location address.
E.g -E 0200
D (Display or Dump)
Displays the contents of a portion memory ni hex and ASCII forms starting with the given address
E.g. -D 0200
A (Assemble)
Allows you to create a program in mnemonic or symbolic code.
E.g. -A 0100
T (Trace)
Runs he program in single-step mode. It also displays the new values of the registers and the next instruction to be executed.
E.g -T
G (Go)
Runs the program as a whole in memory an displays the output
E.g. -G
U (Unassemble)
Lists all the instructions contained in the program beginning at the given address. You can also specify the last address location.
E.g. -U 0100
-U 0100 0109
N (Name)
Gives a name to your program, coded as N <path> <filename>
Extention nae is .COM
E.g. -N A:SAMPLE.COM
W (Write)
Saves the program onto disk storage
E.g. -W
BASIC ASSEMBLY INSTRUCTIONS USED IN DEBUG
MOV (Move Data)
Copies and transfers data between two registers, or between an immediate data to a register
Format: MOV <register>, <register>
MOV <register>, <immediate data>
Example: MOV AX, BX
MOV CX, 5083
MOV CL, DL
MOV BL, 33
ADD (Add Data)
Used to get the sum of two registers or a register and an immediate data, and stores the result to the left most register
Format: ADD <register>, <register>
ADD <register>, <immediate data>
Example: ADD CX, BX
ADD AX, 0308
ADD AL, BL
ADD DH, 85
MUL (Multiply Data)
It is used to get the product of a given register and AX register, and stores the result to AX register. If the product is greater than 16 bits, the overflow is stored in DX register.
Format: MUL <register>
Example: MUL CX
DIV (Divide Data)
Used to divide the value of a given register and AX register, stores the quotient to AX and the remainder to DX registers respectively
Format: DIV <register>
Example DIV BX
INC (Increment by One)
Used to increase the value of the register by one (1).
Format: INC register
Example: INC AX
INC CH
DEC (Decrement by One)
Opposite of INC, decreases the value of the register by one (1).
Format: DEC <register>
Example: DEC AX
DEC CH
LOOP (Loop Until Complete)
It controls the execution of a program segment in a specified number of times.
The CX register should contain a count value before starting the loop and automatically decrements by one (1)
If CX is not equal to zero (0), it transfers to its operand address which points to the start of the loop; otherwise it drops to the nest instruction.
Format: LOOP <offset address>
Example: LOOP 0108
CODING ASSEMBLY LANGUAGE IN TASM
Comment
Ignored by the assembler.
Can improve program’s readability and clarity
Begins with a semicolon (
Ways to include comment
Any statement whose first non-block character is a semicolon
Example:
; This program displays Hello, World!
At the end of an instruction
Example:
MOV AX, 8053H ;initializes the value of AX to 8053
Reserved Words
Words in which the assembler assigns a special meaning and it cannot be used as identifiers
Using reserved words for a wrong purpose causes the assembler to generate an error message
Categories of reserved words
Instructions
Statements that will be translated into machine language and executed by the computer.
Examples:
MOV ADD SUB
MUL DIV INC
DEC LOOP CMP
Directives
Statements that give information to the assembler
Sometimes called pseudo-ops
Examples:
TITLE DOSSEG .MODEL
.STACK .DATA .CODE
Rules in Constructing Valid identifier
It must use letters (A...Z, a…z), number (0…9) and/or special characters like underscore (_), question mark (?) and at sign (@).
It must always start with a letter
It must not use reserved words
It must not exceed to 31 character.
Examples of valid identifiers:
neym r2d2
num_1 msg8
Examples of invalid identifiers:
title num-1
4ever
Statement
May begin anywhere on the line
Each line can only contain one statement
Assembly is not case sensitive
Examples:
ADD AX, BX ; uses 2 operands
DEC CX ; uses
RET ; no operand
Most common directives
TITLE
It creates a title (up to 60 characters) of a source listing.
Format:
TITLE <TEXT>
Examples:
TITLE This program displays Kumusta, BUPC!
TITLE PROGRAM1.ASM
.MODEL
It specifies and initializes the memory model before defining any segment
Format:
.MODEL <memory-model>
Examples:
.MODEL TINY
.MODEL SMALL
.MODEL MEDIUM
.STACK
It defines the size of the attack. The default stack size is 1,024 bytes which you can overrule.
Format:
.STACK <size>
Example:
.STACK 0100h
.DATA
It defines and marks the beginning of data segment
Format:
.DATA
Example:
.DATA
.CODE
It defines and marks the code segment which consists of a set of instructions.
Format:
.CODE
Example:
.CODE
START:
Defines the start of program execution
Format:
START:
Examples:
START:
END
It is placed at the last line of the source code
Format:
END
Example:
END START
STRING
Used for descriptive data such as person’s name or simply a message.
It must end with dollar ($) symbol and defined in double quotation marks (“ “).
DB is the conventional format for defining string of any length.
Example:
neym db “Louis Vuitton$”
Numeric Constant
Used to define arithmetic values and memory address.
It is defined with a radix specifier such as d for decimal, b for binary and h for hexadecimal.
Example:
msg db “Bon jour, monsieur!”, 0Ah, 0Dh, “$”
msg db “Bon jour, monsieur!”, 10d, 13d, “$”
msg db “Bon jour, monsieur!”, 00001010b, 00001101b, “$”
Screen Processing
The monitor
A typical video screen has 80 columns numbered form 0 to 79 and 25 rows numbered from 0 to 24.
Clearing the screen in Assembly Approach
Interrupt 10h and function 06h handles the process of clearing the screen and scrolling
Clear all or part of display beginning at any screen location and ending at any higher-numbered location.
Sample code shows how to clear screen code in assembly
MOV AX, 0600h ; AH = 00h (scroll), AL, 00h (Full screen)
MOV BH, 07h ; 0 (BLACK BACKGROUND), 7 (WHITE TEXT COLOR)
MOV CX, 0000h ; CH = 00H (ROW), CL, 00H (COLUMN)
MOV DX, 184Fh ; DH = 18H (ROW), DL=4FH (COLUMN)
INT 10h ; CALL INTERRUPT SERVICE
SETTING THE CURSOR FUNCTION
Interrupt 10h is the BIOS operation for screen handling and function 02h tells the operation to set the cursor
Its position determines where the next character is to be displayed.
MOV AH, 02H ; REQUEST TO SET THE CURSOR POSITION
MOV BH, 00H ; PAGE NUMBER 0
MOV DH, 0AH ; ROW - 10 IN DECIMAL
MOV DL, 08H ; COLUMN = 8 IN DECIMAL
INT 10H
MAY CONTINUATION PA PO ITO, WAIT NYO LANG
Press thanks kung nakatulong,
Accepting Requests for Tutorial in any Programming Languages
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