Exam 1

direct addressing visualized

(EA) = (A)

ACC

(accumulator machine) has one processor register, requires load/operate/store instructions

ALU

(arithmetic logic unit) functional unit that executes arithmetic and logical computations (has no registers)

CPU

(central processing unit) two parts: 1) datapath: data registers (temp memory), and function units 2) control logic: sequencing of datapath actions

DRAM

(dynamic random access memory) one-dimensional, main memory

von Neumann cycle

(fetch/execute cycle) 1) fetch instruction from memory 2) fetch data required by instruction 3) execute instruction 4) store results in memory 5) repeat

MAR

(memory address register) CPU register in the bus interface unit that contains the ADDRESS of the memory word that should be read or written

MDR

(memory data register) CPU register in the bus interface unit that contains the VALUE that has been read from or should be written to memory

ROM

(read-only memory) "bootstrap" loader programs and basic I/O

SRAM

(static random access memory) cache memory

IR

- (instruction register) - holds current instruction

PSR

- (processor status register) - indicates results of previous operations (flags)

What changes in the prefixes of binary measurement?

- add an "i" to each regular prefix symbol - take the first two letters of the prefix and add "bi"

indirect addressing

- address field points to memory cell containing the address (pointer to) of the operand

direct addresing

- addressing mode in which the instruction holds the address of the operand (memory word containing the data which is to be accessed) - used for global variable in HLL - PROS: single memory reference to access data, more flexible than immediate

instruction

- basic unit of work in a program - composed of opcode and (possibly) one or more operands

immediate addressing

- instruction contains the value to be used - located in the address field of the instruction - stored in memory immediately after the instruction opcode - kind of like using a constant in HHL - PROS: fast, no memory reference needed - CONS: not flexible, value fixed at compile time

assembler

- program that takes assembly instructions and converts to machine code - creates an object file

assembly language

- symbolic, low-level language of instructions that are mnemonic codes for corresponding machine language instructions - translated by an assember into machine language and is in approximately one-to-one correspondence - instructions composed of opcodes and operands

What does the assembler do on the first pass?

1) increment a location counter for each statement 2) collect label definitions into symbol table w/ corresponding location counter values

What does the assembler do on the second pass?

1) using symbol table, it translates assembly language statements to machine code

M U N P F A powers:

10 ^ -3 -6 -9 -12 -15 -18 (3--)

K M G T P E powers:

10 ^ 3 6 9 12 15 18 (3++)

Ki Mi Gi Ti Pi Ei powers:

2 ^ 10 20 30 40 50 60 (10++)

Why do assemblers have a two pass structure?

Because of forward references.

Why do forward references require a two-pass structure?

Because you encounter a "use" before its "definition" and thus cannot immediately translate the label into its memory address.

PC (program counter)

CPU register that contains the ADDRESS of the memory word from which the next instruction will be FETCHED (points to next instruction)

indirect addressing visualized

EA = (A)

What is the acronym for the big prefixes?

K M G T P E (Karen Made Great Time Pissingoff Eugene)

What is the acronym for the small prefixes?

M U N P F A (Many Unnecessary Names Provide Funny Acronyms)

Who originated the stored program concept?

Mauchly and Eckert

Who was credited with the store program concept?

Von Neumann

mnemonics

abbreviation for an operation

pseudo-op

assembly language statement that doesn't generate a machine instruction, but instead acts as a directive to the assembler

object code

code produced by compiler / assembler

address

consecutive binary integers (unsigned)

symbol table

first pass of accumulator - collects label definitions (variables) and assigns memory address based on counter

register

holds an instruction, storage address or data

branch

if accumulator value (some comparison to 0) branch to given label address

load

instruction that will make a copy of the value in a specified memory word and place it into the accumulator (or other register)

Ki Mi Gi Ti Pi Ei prefixes:

kibi mebi gibi tebi pebi exbi

K M G T P E prefixes:

kilo mega giga tera peta exa

What is the increment for all opcodes add, sub, load, store, and halt?

loc increment 2: add, sub, load, store loc increment 1: halt

load/store machine

machine design that contains a register file and for which the arithmetic/logic instructions identify the registers as sources/destinations rather than memory locations

M U N P F A prefixes:

milli micro nano pico femto atto

opcode

mnemonic name in assembly language or a number in an executable that identifies the operation

operand

name of register and/or info needed to generate memory address

stack machine

operands are on a stack, & push from memory / pop into memory

memory

physical device that stores information temporarily or permanently - contains series of bits grouped into addressable units - data is accessed in memory by naming memory addresses

store

stores value in accumulator at given memory address

label

symbolic name in an assembly program that is used to access data or as a branch target

machine language

the binary form of a program that is directly executed by the computer

K M G T P E numeric values:

thousand million billion trillion quadrillion quintillion

interpreter

translates and executes all at once

compiler

translates statements written in HLL into assembly

word

two-part, defines a symbol address and the value stored at the address

(loc) location counter

variable in the assembler program that contains the ADDRESS at which the next instruction or data word will be PLACED