Q. What is the main difference between 16 bit and 32 bit versions of C/C++ while using in line assembler.

Ans The 32-bit applications are written using Microsoft Visual C/C++ for windows and the 16-bit applications are written using Microsoft C/C++ for DOS. The main difference is that Visual C/C++ for windows is more common today, but does not easily call DOS functions such as INT21H.

Q. Explain data addressing modes (with examples) available in microprocessors.

Ans, Direct Mode:
• Instruction includes memory access.
• CPU accesses that location in memory.
Example:
LDAC 5
Reads the data from memory location 5, and stores the data in the CPU’s accumulator.

Indirect Mode:
• Address specified in instruction contains address where the operand resides.
Example:
LDAC @5 or LDAC (5)
Retrieves contents of location 5, uses it to access memory address.

Register Direct and Register Indirect Modes
• Does not specify a memory address. Instead specifies a register.
Example:
LDAC R
Where R is a register containing the value 5.The instruction copies the value 5 from register and into the CPU’s accumulator.

Immediate Mode
• The operand specified in this mode is the actual data it self.
Example:
LDAC #5
Moves the value 5 into the accumulator.

Implicit Mode
• Does not exactly specify an operand. Instruction implicitly specifies the operand because it always applies to a specific register.
Example:
CLAC
Clears the accumulator, and sets value to zero. No operands needed.

Relative Mode
• Operand supplied is an offset, not the actual address. Added to the contents of the CPU’s program counter register to generate the required address.
Example:
LDAC $5 is located at memory location 10, and it takes up two blocks of memory.
Thus the value retrieved for this instruction will be 12 + 5, and will be stored in the accumulator

Index Mode and Base Address Mode
• Address supplied by the instruction is added to the contents of an index register.
• Base address mode is similar except, the index register is replaced by a base address register.
Example:
LDAC 5(X) where X = 10
Reads data from location (5 + 10) = 15 and stores it in the accumulator.

Q. (i) Convert binary number in two's compliment form 0100 1000
(ii) Convert hexadecimal BCH to decimal

Ans. 01001000 => 10111000
BCH =>1011 1100 => 188.

Q. Write a Program in assembly language to find the largest of n numbers stored in the memory.

Ans
MOV AX, 0000
MOV SI, 0200
MOV CX, [SI]
BACK : INC SI
INC SI
CMP AX, [SI]
JAE GO
MOV AX, [SI]
GO: LOOP BACK
MOV [0251], AX
INT 3.

Q. Write an assembly language program to find one’s complement and two’s complement of an 8-bit number

Ans One’s complement of an 8-bit number
LDA 2501H
CMA
STA 2502H
HLT.
Two’s complement of an 8-bit number
LDA 2501H
CMA
INR A
STA 2502H
HLT.