CS401 Final Term Solved Subjective Set 2 by Junaid

Q1. Define Stack Data Structure? 2 marks

Answer: (Page 67) Stack is a data structure that behaves in a first in last out manner. It can contain many elements and there is only one way in and out of the container. When an element is inserted it sits on top of all other elements and when an element is removed the one sitting at top of all others is removed first

Q2. How many broad categories video services are classified? 2 marks

Answer: (Page 149) Video services are classified into two broad categories; graphics mode services and text mode services.

Q3. What is programmer view of processor? 2 marks

Answer: (Page 32) The processor will blindly go there, where we mention even if it contains data and not code

Q4. INT-14-Serial-READ CHARACTER FORM PORT uses which two 8-bit registers to return to result? 2 marks

Answer: (Page 172) Return: AH = line status AL = received character if AH bit 7 clear

Q5. Difference between two instructions? 3 marks

mov byte [num1],5

mov word [num1],5

Answer: In first instruction, The variable num1 is treated as a byte and similarly 5 is also treated as byte. In 2nd instruction, The variable num1 is treated as a word and similarly 5 is also treated as word.

Q6. Write two different modes of video services of BIOS? Differentiate between both modes? 3 Marks

Answer: (Page 149) Video services are classified into two broad categories; graphics mode services and text mode services. In graphics mode a location in video memory corresponds to a dot on the screen. In text mode this relation is not straightforward. The video memory holds the ASCII of the character to be shown and the actual shape is read from a font definition stored elsewhere in memory

Q7. Define Triple Fault? 3 Marks

Q8. Difference between roles of segment-selector and segment-descriptor? 3 Marks

Answer: (Page 175) Role of selector is to select on descriptor from the table of descriptors and the role of descriptor is to define the actual base address.

Q9. How value of Stack pointer (SP) changes after every PUSH or POP instructions? 5 Marks

Answer: (Page 68) Whenever an element is pushed on the stack SP is decremented by two and when we pop from it, it increments by 2 as in case of decrementing stack. A decrementing stack moves from higher addresses to lower addresses as elements are added in it

Q10. 5 Marks

How to write disk sector using INT 13 service?

Answer: (Page 156) INT 13 - DISK - WRITE DISK SECTOR(S) AH = 03h AL = number of sectors to write (must be nonzero)

Return:

Q11. Write down instructions for data movement and arithmetic operations in Motorola 68K Processor? 5 Marks

Answer: (Page 191) Data Movement EXG D0, D2 MOVE.B (A1), (A2) MOVEA (2222).L, A4 MOVEQ #12, D7 Arithmetic ADD D7, (A4) CLR (A3) (set to zero) CMP (A2), D1 ASL, ASR, LSL, LSR, ROR, ROL, ROXL, ROXR (shift operations)

Q12. 5 Marks

How to load program using INT21 service?

Answer: (Page 165) INT 21 - LOAD AND/OR EXECUTE PROGRAM AH = 4Bh AL = type of load (0 = load and execute) DS:DX -> ASCIZ program name (must include extension) ES:BX -> parameter block Return:

AX = error code

Q13. Difference between serial and parallel communication.

Answer: (Page 171) Serial port is a way of communication among two devices just like the parallel port. The basic difference is that whole bytes are sent from one place to another in case of parallel port while the bits are sent one by one on the serial port in a specially formatted fashion.

Q14. Write brief about INT 13 – Extended READ SERVICES

Answer: (Page 157)

INT 13 - INT 13 Extensions - EXTENDED READ

AH = 42h DL = drive number DS:SI -> disk address packet Return:

Q15. Describe briefly INT 3 functionality.

Answer: (Page 133) INT 3 is a Debug Interrupt. INT 3 has a single byte opcode so it can replace any instruction. This allows it to replace any instruction whatsoever. This is also called break point interrupt.

Q16. How to create or Truncate File using INT 21 Service?

Answer: (Page 161)

INT 21 - CREATE OR TRUNCATE FILE

AH = 3Ch

Return:

AX = file handle or error code