Ch 07: Video Memory & Screen Display

Covers direct text manipulation on 80x25 character screens, calculating screen offsets ((Row * 80 + Col) * 2), attribute byte structure (foreground, background, blink bit), and converting binary values to ASCII strings.

264 Questions264 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 181 – 190 of 264 Questions

Page 19 of 27

Q181

📝 Short Q📘 CS401📑 Lec 7🏷️ LODS (Load String) Instruction and Loop ProcessingMedium🔁⭐💡📄🎓VU🏛️VU

Describe the LODS (Load String) instruction in 8088 assembly language, detailing source segment/index register usage, and explain why LODS is typically used inside a loop rather than with the REP prefix.

💻 assembly Snippet

cld
process_loop:
    lodsb
    cmp al, 0
    jz end_loop
    ; Process character in AL
    jmp process_loop
end_loop:

Q182

📝 Short Q📘 CS401📑 Lec 7🏷️ SCAS (Scan String) Instruction and Search PrefixesHard🔁⭐💡🌟📄🎓VU🏛️VU

Explain the operation of the SCAS (Scan String) instruction in 8088 assembly language, detailing register usage, flag updates, and how it combines with REPE/REPNE prefixes for string searching.

💻 assembly Snippet

mov di, string_ptr
mov al, 0
mov cx, 0xFFFF
cld
repne scasb

Q183

📝 Short Q📘 CS401📑 Lec 7🏷️ MOVS (Move String) Instruction and Memory Block CopyingEasy🔁⭐💡📄🎓VU🏛️VU

Describe the MOVS (Move String) instruction in 8088 assembly language, detailing source and destination register mappings, byte/word variants, and block copy execution using the REP prefix.

💻 assembly Snippet

cld
mov cx, 100
rep movsb

Q184

📝 Short Q📘 CS401📑 Lec 7🏷️ CMPS (Compare String) Instruction and String ComparisonsMedium🔁⭐💡📄🎓VU🏛️VU

Explain the CMPS (Compare String) instruction in 8088 assembly language, detailing register usage, subtraction operation, flag updates, and how REPE/REPNE prefixes enable string comparison.

💻 assembly Snippet

cld
mov cx, 10
repe cmpsb

Q185

📝 Short Q📘 CS401📑 Lec 7🏷️ REP (Repeat) Prefix MechanicsEasy🔁⭐💡📄🎓VU🏛️VU

Explain the function of the unconditional REP (Repeat) prefix in 8088 string instructions, detailing CX register handling, flag preservation, and loop termination.

💻 assembly Snippet

mov cx, 50
rep stosb

Q186

🧠 Long Problem📘 CS401📑 Lec 7🏷️ Conditional String Prefixes: REPE/REPZ vs REPNE/REPNZHard🔁⭐💡🌟📄🎓VU🏛️VU

Compare the conditional string repetition prefixes REPE (REPZ) and REPNE (REPNZ) in 8088 assembly language, detailing dual termination conditions and usage with CMPS and SCAS.

💻 assembly Snippet

repe cmpsb
repne scasb

Q187

🧠 Long Problem📘 CS401📑 Lec 7🏷️ LODS String Processing and Video Memory Rendering SubroutineHard⭐💡🌟📄🎓VU🏛️VU

Write a complete 8088 assembly subroutine using the LODSB instruction to fetch characters sequentially from a null-terminated string at DS:SI and print them directly to VGA text mode video memory at ES:DI.

💻 assembly Snippet

print_string:
    cld
next_char:
    lodsb
    cmp al, 0
    jz done
    mov [es:di], al
    mov byte [es:di+1], 0x07
    add di, 2
    jmp next_char
done:
    ret

Q188

📝 Short Q📘 CS401📑 Lec 7🏷️ LODS and STOS Subroutine Pairing for Block ProcessingMedium🔁⭐💡📄🎓VU🏛️VU

Why is combining the LODS instruction with the REP prefix considered ineffective, and how are LODS and STOS paired inside a loop for string processing?

💻 assembly Snippet

cld
process_loop:
    lodsb
    mov ah, 0x07
    stosw
    loop process_loop

Q189

🧠 Long Problem📘 CS401📑 Lec 7🏷️ String Length Calculation using REPNE SCASBHard🔁⭐💡🌟📄🎓VU🏛️VU

Explain how the SCASB instruction combined with the REPNE prefix calculates the length of a null-terminated string, and why DI points past the null character upon loop termination.

💻 assembly Snippet

mov di, string_data
mov al, 0
mov cx, 0xFFFF
cld
repne scasb
sub di, string_data
dec di

Q190

📝 Short Q📘 CS401📑 Lec 7🏷️ LES and LDS Far Pointer Loading InstructionsMedium🔁⭐💡📄🎓VU🏛️VU

Explain the operation, syntax, and register mechanics of the LES and LDS instructions in 8088 assembly language.

💻 assembly Snippet

les di, [far_ptr]
lds si, [far_ptr]

Ch 07: Video Memory & Screen Display

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