Ch 09: Software Interrupts and DOS/BIOS Services

Covers IVT structure (256 vectors x 4 bytes each = 1KB), pushing flags and CS:IP during interrupt invocation, hooking existing software interrupts, and invoking DOS function calls for disk and character I/O.

174 Questions174 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.

Showing 71 – 80 of 174 Questions

Page 8 of 18

Q71

❓ MCQ📘 CS401📑 Lec 9🏷️ 9.1. Interfacing and Peripherals (DB-9 Serial Port Pinout: Ring Indicator Pin 9)Easy🔁⭐💡📄🎓VU🏛️VU

On a standard 9-pin DE-9 / DB-9 serial RS-232 connector, which pin number is assigned to RI (Ring Indicator)?

Q72

📝 Short Q📘 CS401📑 Lec 9🏷️ 9.1. Interfacing and Peripherals (Input and Output Peripheral Categories)Easy💡📄🎓VU🏛️VU

Briefly categorize and describe the two primary hardware device classifications used in personal computer systems.

Q73

❓ MCQ📘 CS401📑 Lec 9🏷️ 9.1. DOS and BIOS Services (DOS INT 21h Service 0Ah Input Buffer Structure)Easy🔁⭐💡📄🎓VU🏛️VU

When calling DOS `INT 21h` Service `0Ah` (Buffered Keyboard Input), in which byte position of the input buffer is the number of characters actually read returned?

💻 assembly Snippet

; Buffer layout: [Byte 0: Max Size | Byte 1: Actual Count | Byte 2+: String Data]

A.third
B.fourth
C.first
D.second

Q74

❓ MCQ📘 CS401📑 Lec 9🏷️ 9.1. Interfacing and Peripherals (DB-9 Serial Port Pinout: DataSet Ready Pin 6)Easy🔁⭐💡📄🎓VU🏛️VU

On a standard 9-pin DE-9 / DB-9 serial RS-232 connector, which pin number is assigned to DSR (DataSet Ready)?

Q75

❓ MCQ📘 CS401📑 Lec 9🏷️ 9.1. Interfacing and Peripherals (DB-9 Serial Port Pinout: Transmitted Data Pin 3)Easy🔁⭐💡📄🎓VU🏛️VU

On a standard 9-pin DE-9 / DB-9 serial RS-232 connector, which pin number is assigned to TD (Transmitted Data / TXD)?

Q76

📝 Short Q📘 CS401📑 Lec 9🏷️ 9.1. Interfacing and Peripherals (BIOS INT 14h Serial Read Return Registers AH and AL)Easy⭐💡📄🎓VU🏛️VU

Which two 8-bit registers are used by BIOS `INT 14h` Service `02h` (Read Character from Serial Port) to return the result character and line status?

💻 assembly Snippet

mov ah, 02h ; Service 02h: Read character from serial port
mov dx, 0   ; COM1
int 14h     ; AH = Line Status, AL = Character received

Q77

📝 Short Q📘 CS401📑 Lec 9🏷️ 9.1. Interfacing and Peripherals (Device Driver Definition and Function)Easy⭐💡📄🎓VU🏛️VU

What is a device driver in operating systems and computer architecture, and what is its primary function?

Q78

🧠 Long Problem📘 CS401📑 Lec 9🏷️ 9.1. Interfacing and Peripherals (DOS Device Driver Header and Request Header Layout)Hard⭐💡📄🎓VU🏛️VU

Describe the header layout and operational mechanism of a device driver file in DOS, including the device attribute word, strategy routine, interrupt routine, and request header.

💻 assembly Snippet

; DOS Device Driver Header Structure
driver_header:
    next_driver: dd 0xFFFFFFFF ; Pointer to next driver
    dev_attr:    dw 0x8000     ; Device attribute word (Bit 15 = Character device)
    strategy:    dw strat_routine ; Offset to Strategy Routine
    interrupt:   dw intr_routine  ; Offset to Interrupt Routine
    units:       db 0          ; Number of units (0 for character devices)
    reserved:    times 7 db 0  ; Reserved padding zeroes

Q79

🧠 Long Problem📘 CS401📑 Lec 9🏷️ 9.1. Interfacing and Peripherals (Device Drivers Necessity, RAM Disk, and CONFIG.SYS)Hard⭐💡📄🎓VU🏛️VU

Why are device drivers necessary in a computer system given that the system BIOS already contains software routines to communicate with hardware peripherals? Explain with an example such as a RAM Disk driver and how drivers are loaded in DOS.

💻 assembly Snippet

; Example CONFIG.SYS line to load a DOS device driver:
DEVICE=C:\DOS\RAMDRV.SYS 2048 512 64

Q80

❓ MCQ📘 CS401📑 Lec 9🏷️ Programmable Interrupt Controller (8259) and IRQ LinesEasy⭐📄🎓VU🏛️VU

Which Hardware Interrupt Request (IRQ) line on the Programmable Interrupt Controller (8259) is assigned to serial communication port COM2?

💻 assembly Snippet

; Unmasking IRQ 3 for COM2 in PIC mask register
in  al, 0x21
and al, 0xF7    ; Clear bit 3 (IRQ 3 enable)
out 0x21, al

A.IRQ 2
B.IRQ 3
C.IRQ 4
D.IRQ 5

Ch 09: Software Interrupts and DOS/BIOS Services

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

📖 Related CS401 - Computer Architecture and Assembly Language Programming Curriculum Units