Ch 07: Video Memory & Screen Display

Covers direct text manipulation on 80x25 character screens, calculating screen offsets ((Row * 80 + Col) * 2), attribute byte structure (foreground, background, blink bit), and converting binary values to ASCII strings.

264 Questions264 MCQs0 Short Questions0 Long Questions

🎯 Exam Practice Papers

CS401 - Computer Architecture and Assembly Language Programming Examination Practice

Timed practice exam simulation for CS401 - Computer Architecture and Assembly Language Programming.

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📝 Short Q📘 CS401📑 Lec 7🏷️ 7.5. LES and LDS ExampleEasy🔁⭐📄🎓VU🏛️VU

What is the key difference between the LES and LDS instructions in x86 assembly language?

💻 assembly Snippet

lds si, [farPtr]
les di, [farPtr]

❓ MCQ📘 CS401📑 Lec 7🏷️ 7.1. Interrupts and Interrupt HandlingEasy🔁⭐💡📄🎓VU🏛️VU

When a number is divided by zero, a 'Divide-by-Zero' interrupt (Vector 0) is generated. Which statement accurately describes how this interrupt is invoked?

💻 assembly Snippet

MOV BL, 0
DIV BL

A.This interrupt is generated automatically by the CPU
B.INT 0
C.INT 1
D.INT 2

🧠 Long Problem📘 CS401📑 Lec 7🏷️ 7.1. Interrupts and DebuggingHard🔁⭐💡📄🎓VU🏛️VU

Write a complete 8088 assembly language Breakpoint Interrupt Service Routine (INT 3 ISR) that saves the CPU context, accesses the interrupted program's code segment and instruction pointer from the stack, and properly returns execution using the IRET instruction.

💻 assembly Snippet

debugISR:
    push bp
    mov bp, sp
    push ax
    push bx
    push cx
    push dx
    push si
    push di
    push ds
    push es
    sti
    push cs
    pop ds
    mov ax, [bp+4]
    mov es, ax

🧠 Long Problem📘 CS401📑 Lec 7🏷️ 7.1. Interrupts and DebuggingHard🔁⭐💡📄🎓VU🏛️VU

In an 8088 assembly language Breakpoint Interrupt Handler (INT 3 ISR), explain the purpose of decrementing the return IP address saved on the stack, restoring the original opcode, and displaying the saved CPU register context. Complete and annotate the provided code snippet.

💻 assembly Snippet

dec word [bp+2]          ; Decrement return address (IP) on stack
mov di, [bp+2]           ; Load return offset into DI
mov word [opcodepos], di ; Remember return position
mov al, [opcode]         ; Load original opcode
mov [es:di], al          ; Restore original opcode in memory
mov byte [flag], 0       ; Reset flag
call clrscr              ; Clear screen
mov si, 6                ; Pointer to first saved register at bp+6
mov cx, 12               ; Loop count: 12 registers to display
mov ax, 0                ; Screen row 0
mov bx, 5                ; Screen column 5
push ax                  ; Pass row
push bx                  ; Pass column
mov dx, [bp+si]          ; Fetch register value from stack frame

🧠 Long Problem📘 CS401📑 Lec 7🏷️ 7.1. Interrupts and DebuggingHard🔁⭐💡📄🎓VU🏛️VU

In an 8088 assembly language Breakpoint Interrupt Handler (INT 3 ISR), explain the procedure for printing CPU register names and their corresponding values on the display screen. Annotate and complete the provided assembly code snippet that loops through saved register values on the stack and displays them alongside their 4-character register labels.

💻 assembly Snippet

push dx         ; number to be printed
call printnum   ; print the number
sub si, 2       ; point to next register
inc ax          ; next row number
loop l3         ; repeat for the 12 registers

mov ax, 0       ; start from row 0
mov bx, 0       ; start from column 0
mov cx, 12      ; total 12 register names
mov si, 4       ; each name length is 4 chars
mov dx, names   ; offset of first name in dx

push ax         ; row number
push bx         ; column number
push dx         ; offset of string
push si         ; length of string
call printstr   ; print the string
add dx, 4       ; point to start of next string
inc ax          ; new row number

🧠 Long Problem📘 CS401📑 Lec 7🏷️ 7.1. Interrupts and DebuggingHard🔁⭐💡📄🎓VU🏛️VU

In 8088 assembly language debugger development, explain how single-step execution is activated using the Trap Flag (TF) inside an Interrupt Service Routine (ISR), and demonstrate how to install INT 1 (Single-Step Interrupt) and INT 3 (Breakpoint Interrupt) handlers into the Interrupt Vector Table (IVT). Annotate and complete the provided assembly code snippet.

💻 assembly Snippet

or word [bp+6], 0x0100 ; set TF in flags on stack
keywait:
  cmp byte [flag], 0   ; has a key been pressed
  je keywait           ; no, check again
  pop es
  pop ds
  pop di
  pop si
  pop dx
  pop cx
  pop bx
  pop ax
  pop bp
  iret

start:
  xor ax, ax
  mov es, ax           ; point es to IVT base
  mov word [es:1*4], trapisr  ; store offset at 1*4
  mov [es:1*4+2], cs          ; store segment at 1*4+2
  mov word [es:3*4], debugisr ; store offset at 3*4
  mov [es:3*4+2], cs          ; store segment at 3*4+2
  cli                  ; disable interrupts

❓ MCQ📘 CS401📑 Lec 7🏷️ 7.1. Dedicated Interrupt VectorsEasy🔁⭐💡📄🎓VU🏛️VU

Which x86 dedicated CPU interrupt vector is reserved for Arithmetic Overflow (INTO instruction)?

💻 assembly Snippet

INTO

A.INT 4
B.INT 1
C.INT 2
D.INT 3

❓ MCQ📘 CS401📑 Lec 7🏷️ 7.1. Interrupts and Fault ExceptionsEasy🔁⭐💡📄🎓VU🏛️VU

Which of the following is a special type of interrupt fault where the saved return IP points to the same instruction that caused the interrupt rather than the next instruction?

💻 assembly Snippet

DIV BL

A.Divide overflow interrupt
B.Debug interrupt
C.Arithmetic overflow interrupt
D.Change of sign interrupt

❓ MCQ📘 CS401📑 Lec 7🏷️ 7.1. Dedicated Interrupt Vectors and Single-SteppingEasy🔁⭐💡📄🎓VU🏛️VU

In x86 assembly language debugging, the Single-Step Interrupt (INT 1) is ________.

💻 assembly Snippet

PUSHF
POP AX
OR AX, 0x0100
PUSH AX
POPF

A.Like divide by zero interrupt
B.Hardware interrupt
C.Like divide by 1 interrupt
D.Software interrupt

Q10

🧠 Long Problem📘 CS401📑 Lec 7🏷️ 7.2. Interrupt Chaining and TSR ProgrammingMedium🔁⭐💡📄🎓VU🏛️VU

What is interrupt chaining? Describe its purpose and execution mechanism.

💻 assembly Snippet

pushf
call far [old_isr]

Ch 07: Video Memory & Screen Display

CS401 - Computer Architecture and Assembly Language Programming Examination Practice

Mid Term Examination

Final Term Examination

CS401 - Computer Architecture and Assembly Language Programming Examination Practice

Mid Term Examination

Final Term Examination

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