2. Definitions

Question 1

instruction set

Answer 1

The vocabulary of commands understood by a given architecture.

Question 2

stored-program concept

Answer 2

The idea that instructions and data of many types can be stored in memory as numbers and thus be easy to change, leading to the stored-program computer.

Question 3

doubleword

Answer 3

Another natural unit of access in a computer, usually a group of 64 bits; corresponds to the size of a register in the LEGv8 architecture.

Question 4

word

Answer 4

A natural unit of access in a computer, usually a group of 32 bits.

Question 5

data transfer instruction

Answer 5

A command that moves data between memory and registers.

Question 6

address

Answer 6

A value used to delineate the location of a specific data element within a memory array.

Question 7

alignment restriction

Answer 7

A requirement that data be aligned in memory on natural boundaries.

Question 8

binary digit. Also called binary bit.

Answer 8

One of the two numbers in base 2, 0 or 1, that are the components of information.

Question 9

least significant bit

Answer 9

The rightmost bit in an LEGv8 doubleword.

Question 10

most significant bit

Answer 10

The leftmost bit in an LEGv8 doubleword.

Question 11

one’s complement

Answer 11

A notation that represents the most negative value by 10 … 000(two)* and the most positive value by 01 … 11(two), leaving an equal number of negatives and positives but ending up with two zeros, one positive (00 … 00(two)) and one negative (11 … 11(two)). The term is also used to mean the inversion of every bit in a pattern: 0 to 1 and 1 to 0.
* As in, base 2.

Question 12

biased notation

Answer 12

A notation that represents the most negative value by 00 … 000(two) and the most positive value by 11 … 11 , with 0 typically having the value 10 … 00(two), thereby biasing the number such that the number plus the bias has a non-negative representation.

Question 13

instruction format

Answer 13

A form of representation of an instruction composed of fields of binary numbers.

Question 14

machine language

Answer 14

Binary representation used for communication within a computer system.

Question 15

hexadecimal

Answer 15

Numbers in base 16.

Question 16

opcode

Answer 16

The field that denotes the operation and format of an instruction.

Question 17

AND

Answer 17

A logical bit-by-bit operation with two operands that calculates a 1 only if there is a 1 in both operands.

Question 18

OR

Answer 18

A logical bit-by-bit operation with two operands that calculates a 1 if there is a 1 in either operand.

Question 19

NOT

Answer 19

A logical bit-by-bit operation with one operand that inverts the bits; that is, it replaces every 1 with a 0, and every 0 with a 1.

Question 20

EOR

Answer 20

A logical bit-by-bit operation with two operands that calculates the Exclusive OR of the two operands. That is, it calculates a 1 only if the values are different in the two operands.

Question 21

conditional branch

Answer 21

An instruction that tests a value and that allows for a subsequent transfer of control to a new address in the program based on the outcome of the test.

Question 22

basic block

Answer 22

A sequence of instructions without branches (except possibly at the end) and without branch targets or branch labels (except possibly at the beginning).

Question 23

branch address table. Also called branch table.

Answer 23

A table of addresses of alternative instruction sequences.

Question 24

procedure

Answer 24

A stored subroutine that performs a specific task based

on the parameters with which it is provided.

Question 25

branch-and-link instruction

Answer 25

An instruction that branches to an address and simultaneously saves the address of the following instruction in a register (LR or X30 in LEGv8).

Question 26

return address

Answer 26

A link to the calling site that allows a procedure to return to the proper address; in LEGv8 it is stored in register LR (X30).

Question 27

caller

Answer 27

The program that instigates a procedure and provides the necessary parameter values.

Question 28

callee

Answer 28

A procedure that executes a series of stored instructions based on parameters provided by the caller and then returns control to the caller.

Question 29

stack

Answer 29

A data structure for spilling registers organized as a last-in-first-out queue.

Question 30

stack pointer

Answer 30

A value denoting the most recently allocated address in a stack that shows where registers should be spilled or where old register values can be found. In LEGv8, it is register SP.

Question 31

program counter (PC)

Answer 31

The register containing the address of the instruction in the program being executed.

Question 32

push/pop (stack)

Answer 32

``` push = Add element to stack. pop = Remove element from stack. ```

Question 33

global pointer

Answer 33

The register that is reserved to point to the static area.

Question 34

procedure frame. Also called activation record.

Answer 34

The segment of the stack containing a procedure’s saved registers and local variables.

Question 35

frame pointer

Answer 35

A value denoting the location of the saved registers and local variables for a given procedure.

Question 36

text segment

Answer 36

The segment of a UNIX object file that contains the machine language code for routines in the source file.

Question 37

PC-relative addressing

Answer 37

An addressing regime in which the address is the sum of the program counter (PC) and a constant in the instruction.

Question 38

addressing mode

Answer 38

One of several addressing regimes delimited by their varied use of operands and/or addresses.

Question 39

data race

Answer 39

Two memory accesses form a data race if they are from different threads to the same location, at least one is a write, and they occur one after another.

Question 40

assembly language

Answer 40

A symbolic language that can be translated into binary machine language.

Question 41

pseudoinstruction

Answer 41

A common variation of assembly language instructions often treated as if it were an instruction in its own right.

Question 42

symbol table

Answer 42

A table that matches names of labels to the addresses of the memory words that instructions occupy.

Question 43

linker. Also called link editor.

Answer 43

A systems program that combines independently assembled machine language programs and resolves all undefined labels into an executable file.

Question 44

executable file

Answer 44

A functional program in the format of an object file that contains no unresolved references. It can contain symbol tables and debugging information. A “stripped executable” does not contain that information. Relocation information may be included for the loader.

Question 45

loader

Answer 45

A systems program that places an object program in main memory so that it is ready to execute.

Question 46

dynamically linked libraries (DLLs)

Answer 46

Library routines that are linked to a program during execution.

Question 47

Java bytecode

Answer 47

Instruction from an instruction set designed to interpret Java programs.

Question 48

Java Virtual Machine (JVM)

Answer 48

The program that interprets Java bytecodes.

Question 49

Just In Time compiler (JIT)

Answer 49

The name commonly given to a compiler that operates at runtime, translating the interpreted code segments into the native code of the computer.

Question 50

object-oriented language

Answer 50

A programming language that is oriented around objects rather than actions, or data versus logic.

Question 51

loop-unrolling

Answer 51

A technique to get more performance from loops that access arrays, in which multiple copies of the loop body are made and instructions from different iterations are scheduled together.

Question 52

public (Java)

Answer 52

A Java keyword that allows a method to be invoked by any other method.

Question 53

protected (Java)

Answer 53

A Java keyword that restricts invocation of a method to other methods in that package.

Question 54

package (Java)

Answer 54

Basically a directory that contains a group of related classes

Question 55

static method (Java)

Answer 55

A method that applies to the whole class rather than to an individual object. It is unrelated to static in C.

Question 56

general-purpose register (GPR)

Answer 56

A register that can be used for addresses or for data with virtually any instruction.

Question 57

accumulator

Answer 57

Archaic term for register. On-line use of it as a synonym for “register” is a fairly reliable indication that the user has been around quite a while.

Question 58

load-store architecture. Also called register-register architecture.

Answer 58

An instruction set architecture in which all operations are between registers and data memory may only be accessed via loads or stores.