CS401 Paper

Assembly Language Paper – CS401

1. Division by zero is done by which interrupt.
2. Define Hardware Interrupt & I/O ports (5 marks)
3. Five BIOS video services used in text mode (3 marks)
4. DOS allocate memory for program execution and then de-allocate, explain memory management in DOS (10 marks)

1. BL contains 5 decimal then after right shift , BL will become

 3v
 2.5v
 5v
 10v
2. 8 * 16 font is stored in ________ bytes.

 3v
 4v
 8v
 16v
3. In DOS input buffer , number of characters actually read on return is stored in

 First bytev
 Second bytev
 Third bytev
 Fourthv byte
4. IRQ 0 has priority

 Lowv
 Highv
 Highestv
 Mediumv
5. Thread registration code initialize PCB and add to linked list so that _____ will give it turn.
 Assemblerv
 Linkerv
 Schedulerv
 Debuggerv
6. Traditional calling conventions are in ______ number
 1v
 2v
 3v
 4v
7. VESA VEB 2.0 is standard for
v High Resolution Mode
 Lowv Resolution Mode
 Very High Resolution Modev
 Mediumv Resolution Mode
8. To clear direction flag which instruction is used

 Cldv
 Clrdv
 Cl dfv
 Clr dfv
9. In STOSW instruction , When DI is cleared , SI is

v Incremented by 1
 Incremented by 2v
v Decremented by 1
 Decremented by 2v
10. Interrupt that is used in debugging with help of trap flag is

 INT 0v
 INT 1v
 INT 2v
 INT 3v
11. INT for arithmetic overflow is
 INT 1v
 INT 2v
 INT 3v
 INT 4v
12. IRQ referred as

 Eight Input signalsv
 One Inputv signal
 Eight Output signalsv
 One output signalv


13. IRQ for keyboard is _________
14. IRQ for sound card is _____________
15. IRQ for floppy disk is _____________
16. IRQ with highest priority is
 Keyboardv IRQ
 Timer IRQv
 Sound Cardv
 Floppy Diskv


17. Pin for parallel port ground is
 10-18v
 18-25v
 25-32v
 32-39v
18. The physical address of Interrupt Descriptor Table (IDT) is stored in
 GDTRv
 IDTRv
 IVTv
 IDTTv
19. Execution of “RET 2” results in?
20. CX register is
 Count registerv
 Datav register
 Index registerv
 Base registerv
21. OUT instruction uses _______ as source register.
22. IN DB-9 connector the Data Set ready pin is at
 5v
 6v
 7v
 8v
23. If two devices uses same IRQ then there is
v IRQ collision
 IRQ conflictv
 IRQ dropv
24. VESA organizes 16 bit color for every pixel in ratio
 5:5:5v
 5:6:5v
 6:5:6v
 5:6:7v

There was fill in blanks question with 10 marks. The choice was given at bottom.

25. Serial Port is also accessible via ______ ports, _________ is accessible via ports 3F8-3FF while _______ is accessible via 2F8 -2FF.
The first register at 3F8 is the _________ holding register if written to and the receiver ______ register if read from.
Other register of our interest include 3F9 whose ______ must be set to enable received data available interrupt and ________ must be set to enable transmitter holding register empty interrupt.
(Transmitter, COM 1 , I/O ports , COM2. bit 0 , Buffer , 3FA)