Ch 04: Bit Manipulation and Shifts

Covers bitwise logic manipulations, clearing/setting/toggling specific bits, arithmetic vs logical shifts, fast multiplication and division algorithms by powers of 2, and extended-precision math.

198 Questions198 MCQs0 Short Questions0 Long Questions

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CS401 - Computer Architecture and Assembly Language Programming Examination Practice

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

Showing 191 – 198 of 198 Questions

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Q191

📝 Short Q📘 CS401📑 Lec 4🏷️ 4.2. Bit Manipulation & ShiftingEasy⭐💡📄🎓VU🏛️VU

Summarize the core loop logic of the Shift-and-Add Binary Multiplication Algorithm and explain the role of the Carry Flag (CF) during each iteration.

💻 assembly Snippet

; Shift-and-Add Core Loop
shr cx, 1       ; Shift multiplier LSB into CF
jnc skip_add    ; If CF == 0, skip addition
add ax, bx      ; Add multiplicand if CF == 1
skip_add:
shl bx, 1       ; Shift multiplicand left for next bit weight

Q192

📝 Short Q📘 CS401📑 Lec 4🏷️ 4.2. Bit Manipulation & ShiftingHard⭐💡📄🎓VU🏛️VU

Why does multiplying two 16-bit numbers require 32-bit register space and 32-bit shifting/addition operations, and what occurs if a 16-bit multiplicand is shifted in 16-bit registers?

💻 assembly Snippet

; Zero-extending 16-bit multiplicand into 32-bit DX:AX space
mov ax, [multiplicand] ; Lower 16 bits in AX
xor dx, dx             ; Upper 16 bits cleared in DX (DX:AX = 32-bit multiplicand)

Q193

📝 Short Q📘 CS401📑 Lec 4🏷️ 4.2. Bit Manipulation & ShiftingMedium⭐💡📄🎓VU🏛️VU

What is meant by a 'valuable bit' in binary extended shift operations, and how does zero-extension protect valuable bits during multi-bit left shifts?

💻 assembly Snippet

; Zero-extension protects valuable bits during shifting
; Initial 32-bit space: 0000 0000 0000 0000 | 1000 0000 0000 0001 b
; Shifting left moves '1' bits into upper word without bit loss

Q194

📝 Short Q📘 CS401📑 Lec 4🏷️ 4.2. Bit Manipulation & ShiftingMedium⭐💡📄🎓VU🏛️VU

How is 32-bit extended left shifting performed on a doubleword in 16-bit 8086 assembly language using SHL and RCL?

💻 assembly Snippet

; Extended 32-bit Left Shift Example
num1 dd 40000
shl word [num1], 1    ; Shift lower 16-bit word left (MSB -> CF)
rcl word [num1+2], 1  ; Rotate upper 16-bit word left through carry (CF -> LSB)

Q195

📝 Short Q📘 CS401📑 Lec 4🏷️ 4.3. Extended OperationsEasy⭐💡📄🎓VU🏛️VU

What is the ADC (Add with Carry) instruction in 8086 assembly language, how does it differ from ADD, and how is it used for multi-word (32-bit) addition?

💻 assembly Snippet

; 32-bit Extended Addition (DX:AX + CX:BX)
add ax, bx    ; Add lower 16 bits (AX = AX + BX, sets CF if carry)
adc dx, cx    ; Add upper 16 bits + CF (DX = DX + CX + CF)

Q196

📝 Short Q📘 CS401📑 Lec 4🏷️ 4.3. Extended OperationsMedium⭐💡📄🎓VU🏛️VU

How does extended subtraction operate in 8086 assembly language using SUB and SBB (Subtract with Borrow)?

💻 assembly Snippet

; 32-bit Extended Subtraction (DX:AX - CX:BX)
sub ax, bx    ; Subtract lower 16 bits (sets CF if borrow needed)
sbb dx, cx    ; Subtract upper 16 bits and borrow (DX = DX - CX - CF)

Q197

📝 Short Q📘 CS401📑 Lec 4🏷️ 4.3. Extended OperationsMedium⭐💡📄🎓VU🏛️VU

Write an 8086 assembly language code snippet to add two 32-bit doubleword variables ('src' and 'dest') in memory using ADD and ADC, and explain how carry propagation works between lower and upper words.

💻 assembly Snippet

; 32-Bit DoubleWord Addition Memory Example
dest: dd 40000
src:  dd 80000

mov ax, [src]          ; Load lower 16 bits of src
add word [dest], ax    ; Add lower 16 bits of dest and src (sets CF)
mov ax, [src+2]        ; Load upper 16 bits of src
adc word [dest+2], ax  ; Add upper 16 bits + CF into dest+2

Q198

📝 Short Q📘 CS401📑 Lec 4🏷️ 4.3. Extended OperationsMedium⭐💡📄🎓VU🏛️VU

How does the SBB (Subtract with Borrow) instruction function in multi-word extended subtraction, and what dual roles does the Carry Flag (CF) perform during addition and subtraction?

💻 assembly Snippet

; 32-Bit DoubleWord Subtraction Example
mov ax, [src]          ; Load lower 16 bits of src
sub word [dest], ax    ; Subtract lower words (sets CF if borrow needed)
mov ax, [src+2]        ; Load upper 16 bits of src
sbb word [dest+2], ax  ; Subtract upper words minus borrow (dest+2 = dest+2 - ax - CF)

Ch 04: Bit Manipulation and Shifts

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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