Week 5

Question 1

Characteristics of HLL

Answer 1

One to many translation, hardware independent, application orientation, strongly omits hardware details, designed for programmer productivity, source code requiring translation is written in HLL

Question 2

Characteristics of LLL

Answer 2

One to one translation, hardware dependent, systems programming orientation, few abstractions, special purpose, assembly code(LLL) is the result of translation by a compiler

Question 3

Assembly Language

Answer 3

1. Translated by an assembler
2. Many assembly languages exist as it uses the instruction set and operands from a single processor, share the same fundamental structure.
3. Programmer can switch between assembly languages quickly
4. A single statement corresponds to a single machine instruction

Question 4

Assembly Language Syntax

Answer 4

label: op result, operand1, operand2, … ; comment

Question 5

Label (Assembly Language)

Answer 5

1. Symbolic for the memory address pointing to the location storing this instruction
2. Optional label used for branching

Question 6

Op (Assembly Language)

Answer 6

Mnemonic for the operation to perform; one of the possible instructions

Question 7

Operand (Assembly Language)

Answer 7

Specifies an operand for the instruction; usually a pointer or immediate value

Question 8

Operand Order

Answer 8

Target register on the left, source register on the right

Question 9

Register Names

Answer 9

Example of naming register 10: $10, R10, r10

Question 10

Memory Pointer Syntax

Answer 10

Example of loading a register (r2) from memory at the location pointed to by register r1: ldr r2, (r1)

Question 11

Operand Types

Answer 11

Immediate, Reference to register, Reference to memory

Question 12

Block Comment

Answer 12

Explain purpose of and detail register and memory use for a code section

Question 13

Line comment

Answer 13

Explain purpose of one instruction

Question 14

Conditional Execution

Answer 14

Code that may or may not be executed depending on a certain condition

Question 15

Branch Instruction

Answer 15

if (expression) {
PC(Current Instruction ptr) + Offset: This is the branch target addy
else {
PC = PC + sizeof(instr.(usually 4 bytes))

Question 16

Offset

Answer 16

Bytes between Branch instruction first byte and target instruction first byte

Question 17

Assembler

Answer 17

Translates assembly language programs into binary code for the processor to execute

Question 18

Assembler vs. Compiler

Answer 18

Similarities: Both translate a source program into equivalent binary code
Differences: Compiler has more freedom to choose which values are stored in registers and allocation of variables to memory, whereas an assembler is a one-to-one translation

Question 19

Two-pass Algorithm

Answer 19

Assembler follows this: First pass stores label names and its relative memory address in a symbol table; also stores locations for each statement. The second pass constructs machine code bit strings by using labels & locations calculated by first pass

Question 20

One-pass Algorithm

Answer 20

Compilers follow this: Compilation is intensive and declaring and defining is much more readable

Question 21

Fall through instruction

Answer 21

Default next instruction after a branch instruction

Question 22

Where is increment for a for loop in assembly

Answer 22

After the code that performs the body

Question 23

Overhead

Answer 23

Additional computational work that occurs due only to the use of a fixed iteration loop

Question 24

jsr

Answer 24

Saves the current location and branches to a subroutine at a specified location

Question 25

ret

Answer 25

Causes the processor to return to the previously saved location

Question 26

Amdahl’s Law

Answer 26

Speedup Overall = Original Execution Time / Execution time using enhancement

Question 27

fe

Answer 27

Fraction enhanced, the portion of the original execution sped up; 0 <= fe <= 1

Question 28

Se

Answer 28

Speedup when the enhancement is in use; Se = Time to execute fe without enhancement / Time to execute fe with use of enhancement

Question 29

Where is HLL in the compilation process?

Answer 29

source code requiring translation is written with HLL

Question 30

Where is assembly in the compilation process?

Answer 30

assembly code is the result of translation by COMPILER

Question 31

List 3 problems that occur from manual offset computation:

Answer 31

1) Programmer error in offset calculation breaks program
2) programmer deletes or inserts an instruction between branch and target (offset must be revised because number of bytes between branch and target has changed)
3) Programmer productivity and happiness decline

Question 32

knowing that jsr occupies locations 0x0C - 0x0F in memory, what is the sign magnitude decimal offset value and using it to go to label3, if label3 occupies locations 0x18 - 0x1B?

Answer 32

+12 (Week 5 slide 27 for more examples)

Question 33

Two-pass makes _____ references

Answer 33

forward references (undefined references), not an error; they resolve eventually

Question 34

assembly branches when previous compare is _____

Answer 34

false

Question 35

How do you fetch sequentially next fast?

Answer 35

1) Dedicate hardware outside the ALU to speed the computation of the pointer to the most common next machine instruction, call it the Default Next Instruction Pointer
2) Design the Default_Next_Instruction_Pointer circuit for a processor with a 4-byte, fixed-length machine instruction format