Assembly Language Programming

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Questions and Answers

What is the purpose of the PROC directive in assembly language?

The PROC directive is used to identify the start of a procedure.

How is the type of procedure specified after the PROC directive?

The type of procedure is specified using the terms 'near' or 'far' after the PROC directive.

What does the FAR term indicate when used with the PROC directive?

The FAR term indicates that the procedure is located in a segment with a different name from the one that contains the calling instructions.

How is the ENDP directive used in assembly language?

The ENDP directive is used to indicate the end of a procedure to the assembler. Signup and view all the answers

What is the purpose of using the ENDP directive along with the PROC directive?

The ENDP directive, along with the PROC directive, is used to 'bracket' a procedure. Signup and view all the answers

Explain the purpose of the INT instruction in BIOS or DOS.

The INT instruction is used to invoke subroutines within BIOS or DOS by saving CS:IP and flags on the stack and going to the subroutine associated with the specified interrupt number. Signup and view all the answers

What is the format of the INT instruction and what is the range of the interrupt number?

The format of the INT instruction is INT xx, where xx is the interrupt number in the range of 00-FFH, providing a total of 256 interrupts. Signup and view all the answers

What are the widely used interrupts associated with INT 10H and INT 21H used for?

INT 10H is used for screen video communication, while INT 21H is used for requesting various services from DOS. Signup and view all the answers

Explain the requirements for using the services of INT 10H and INT 21H.

Before requesting the services of INT 10H and INT 21H, certain registers must have specific values depending on the function being requested. Signup and view all the answers

What is the function of INT 10H Function 06 and what are the specific register values required for this function?

INT 10H Function 06 is used for scrolling the window and clearing it. The specific register values required are AL for the number of lines to scroll, BH for the attribute of blank rows, CH and CL for the upper row and left column, and DH and DL for the lower row and right column. Signup and view all the answers

What is the purpose of the PROC directive in assembly language?

The PROC directive is used to identify the start of a procedure. Signup and view all the answers

How is the type of procedure specified after the PROC directive?

The type of procedure is specified by using the term near or the term far after the PROC directive. Signup and view all the answers

What does the FAR term indicate when used with the PROC directive?

The FAR term indicates that the procedure is located in a segment with a different name from the one that contains the instructions which call the procedure. Signup and view all the answers

What is the purpose of the ENDP directive in assembly language?

The ENDP directive is used to indicate the end of a procedure to the assembler. Signup and view all the answers

How is the ENDP directive used in conjunction with the PROC directive?

The ENDP directive is used with the PROC directive to 'bracket' a procedure. Signup and view all the answers

Study Notes

PROC Directive in Assembly Language

Defines a procedure or function within an assembly language program.
Specifies the type of procedure (e.g., near or far) immediately after the PROC keyword.
"FAR" indicates that the procedure can be called from a different segment; it includes both a segment and an offset.

ENDP Directive

Marks the end of a procedure defined by the PROC directive.
Used to define the scope of the procedure, allowing the assembler to know where the procedure concludes.
Essential for maintaining structure and organization in assembly code.

INT Instruction in BIOS or DOS

Performs software interrupts to access BIOS or DOS services.
INT instruction format: INT <interrupt_number>; the range of interrupt numbers is typically 00H to FFH.

Common Interrupts

INT 10H: Handles video display services (graphics and text operations).
INT 21H: Provides file handling and DOS service functions (input/output operations).

Requirements for INT 10H and INT 21H

Registers must be set up with the correct values before invoking the interrupt.
Specific function numbers selected through specific registers dictate the desired service.

INT 10H Function 06

Used for direct screen manipulation, specifically to scroll the window up in text mode.
Required register values:
- AH = 06H to indicate the scroll up function.
- AL = number of lines to scroll.
- BH = character attribute for filling spaces if under-scrolling occurs.
- CX = starting line number.
- DX = ending line number.

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Description

Test your knowledge of PROC (PROCEDURE) directive in assembly language programming with this quiz. Explore the usage and syntax of PROC directive, as well as its role in defining and organizing procedures within a program.