CHAPTER 3: Instructions Flashcards
instruction set
vocabulary of commands understood by a given architecture
stored-program concept
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
word
natural unit of access in a computer, usually a group of 32 bits
doubleword
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
Design Principle 2: Smaller is faster
- a very large number of registers may increase the clock cycle time simply because it takes electronic signals longer when they must travel farther
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data transfer instruction
command that moves data between memory and registers
address
value used to delineate the location of a specific data element within a memory array
data transfer instruction
command that moves data between memory and registers
address
value used to delineate the location of a specific data element within a memory array
memory
is just a large, single-dimensional array, with the address acting as the index to that array, starting at 0
alignment restriction
requirement that data be aligned in memory on natural boundaries
binary number
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least significant bit
rightmost bit in an LEGv8 doubleword
most significant bit
leftmost bit in an LEGv8 doubleword
two’s complement
signed number representation where a leading 0 indicates a positive number and a leading 1 indicates a negative number. The complement of a value is obtained by complementing each bit (0 → 1 or 1 → 0), and then adding one to the result
one’s complement
notation that represents the most negative value by 10 … 000two and the most positive value by 01 … 11two, leaving an equal number of negatives and positives but ending up with two zeros, one positive (00 … 00two) and one negative (11 … 11two). The term is also used to mean the inversion of every bit in a pattern: 0 to 1 and 1 to 0
biased notation
notation that represents the most negative value by 00 … 000two and the most positive value by 11 … 11two, with 0 typically having the value 10 … 00two, thereby biasing the number such that the number plus the bias has a non-negative representation
instruction format
form of representation of an instruction composed of fields of binary numbers
machine language
binary representation used for communication within a computer system
hexadecimal
Numbers in base 16 that are easy to convert to binary
opcode
field that denotes the operation and format of an instruction
and
logical bit- by-bit operation with two operands that calculates a 1 only if there is a 1 in both operands
mask
“conceals” some bits
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or
logical bit-by-bit operation with two operands that calculates a 1 if there is a 1 in either operand
not
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
EOR (exclusive or)
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