Architecture 02

Question 1

What is assembly language?

Answer 1

A given assembly language uses the instruction set and operands from a single processor. Thus, many assembly languages exist, one for each processor.

Question 2

What is an assembler?

Answer 2

Converts assembly language for ISA to more detailed object code.

Question 3

What is a compiler?

Answer 3

Software that converts high-level program into low level instructions for specific machine, and is not (usually) needed at run time.

Question 4

What is an interpreter?

Answer 4

Software that reads a high-level program and carries it out. This is done at run time.

Question 5

What is a linker?

Answer 5

• Combines object code files together to make an executable program that can actually run.
• It incorporates necessary library object code files.
• It determines memory offsets for functions in different files.

Question 6

What is a loader?

Answer 6

• Software that loads programs and libraries into memory to prepare them for execution
• It’s provided by the OS
• Which also provides access to hardware resources

Question 7

What is a register?

Answer 7

A small, high-speed hardware storage device found in a processor. A register has a fixed size and supports two basic operations: fetch and store.

Question 8

What is a general-purpose register?

Answer 8

• Used as a temporary storage mechanism
• There are usually only a small number of them
• Each register is usually the size of an integer.

Question 9

What is meant by “orthogonality”?

Answer 9

An ISA is orthogonal if each instruction perform a unique task without overlapping with other instructions.

Question 10

What is an operand?

Answer 10

Things the CPU can apply operations to, like registers

Question 11

What is meant by register-memory?

Answer 11

• At least one instruction argument can come straight from memory
• More expressive, less need to find registers to store things in

Question 12

What is meant by register-register (load-store)?

Answer 12

• All operations work between registers
• Only data transfer operations access memory
• Separation of memory access and arithmetic functions makes design simpler

Question 13

Explain what is meant by an operation taking 3 operands

Answer 13

• Operation specifies both inputs and an output location
• e.g Add x to y, store in z
• Instructions get longer, more memory access required

Question 14

Explain what is meant by an operation taking 2 operands

Answer 14

• Result replaces one input

* e.g Add x to y, changing y

Question 15

Explain what is meant by an operation taking 1 operand

Answer 15

• All operations modify an “accumulator”

* e.g Add x to the “accumulator”

Question 16

Explain what is meant by an operation taking 0 operands

Answer 16

• Manipulating the stack directly

* e.g Replace the top two numbers of the stack by their sum

Question 17

What is an opcode?

Answer 17

• Short for operation code, refers to the exact operation to be performed
• Each operation must be given a unique opcode by the ISA (i.e integer addition might be 5)

Question 18

What are the advantages of having fixed-length instructions over variable-length instructions?

Answer 18

• Variable length instructions instructions require complex hardware to fetch and decode
• Fixed length instructions are easy to fetch and decode, and the hardware can compute the location of the next instruction easily.