CHAPTER 2: Computer Abstract / Tech Flashcards
personal computer (PC)
A computer designed for use by an individual, usually incorporating a graphics display, a keyboard, and a mouse
server
A computer used for running larger programs for multiple users, often simultaneously, and typically accessed only via a network
supercomputer
A class of computers with the highest performance and cost; they are configured as servers and typically cost tens to hundreds of millions of dollars
embedded computer
A computer inside another device used for running one predetermined application or collection of software
personal mobile devices (PMD)
small wireless devices to connect to the Internet; they rely on batteries for power, and software is installed by downloading apps. Conventional examples are smart phones and tablets
cloud computing
large collections of servers that provide services over the Internet; some providers rent dynamically varying numbers of servers as a utility
Software as a Service (SaaS)
delivers software and data as a service over the Internet, usually via a thin program such as a browser that runs on local client devices, instead of binary code that must be installed, and runs wholly on that device. Examples include web search and social networking
multicore microprocessor
microprocessor containing multiple processors (“cores”) in a single integrated circuit
acroynm
word constructed by taking the initial letters of a string of words. For example: RAM is an acronym for Random Access Memory, and CPU is an acronym for Central Processing Unit
terabyte (TB)
1,099,511,627,776 (240) bytes, although communications and secondary storage systems developers started using the term to mean 1,000,000,000,000 (1012) bytes
tebibyte (TiB)
240 bytes, defining terabyte (TB) to mean 1012 bytes. The figure below shows the full range of decimal and binary values and names
systems software
software that provides services that are commonly useful, including operating systems, compilers, loaders, and assemblers
operating system
supervising program that manages the resources of a computer for the benefit of the programs that run on that computer
compiler
program that translates high-level language statements into assembly language statements
binary digit (bit)
one of the two numbers in base 2 (0 or 1) that are the components of information
instruction
command that computer hardware understands and obeys
assembly
program that translates a symbolic version of instructions into the binary version
assembly language
symbolic representation of machine instructions
machine language
binary representation of machine instructions
high-level programming language
portable language such as C, C++, Java, or Visual Basic that is composed of words and algebraic notation that can be translated by a compiler into assembly language
input device
mechanism through which the computer is fed information, such as a keyboard
output device
mechanism that conveys the result of a computation to a user, such as a display, or to another computer
consumer-oriented embedded applications
- dependability should be achieved through simplicity - emphasis on doing on function as perfectly as possible
touchscreen
people are electrical conductors, if an insulator like glass is covered with a transparent conductor, touching distorts the electrostatic field of the screen, which results in a change in capacitance
input device
mechanism through which the computer is fed information, such as a keyboard
output device
mechanism that conveys the result of a computation to a user, such as a display, or to another computer
liquid crystal display (LCD)
display technology using a thin layer of liquid polymers that can be used to transmit or block light according to whether a charge is applied
active matrix display
liquid crystal display using a transistor to control the transmission of light at each individual pixel
pixel
smallest individual picture element. Screens are composed of hundreds of thousands to millions of pixels, organized in a matrix
integrated circuit (chip)
device combining dozens to millions of transistors
central processor unit (CPU)
active part of the computer, which contains the datapath and control and which adds numbers, tests numbers, signals I/O devices to activate, and so on
datapath
component of the processor that performs arithmetic operations
memory
storage area in which programs are kept when they are running and that contains the data needed by the running programs
dynamic random access memory (DRAM)
memory built as an integrated circuit; it provides random access to any location. Access times are 50 nanoseconds and cost per gigabyte in 2012 was $5 to $10
cache memory
small, fast memory that acts as a buffer for a slower, larger memory
static random access memory (SRAM)
memory built as an integrated circuit, but faster and less dense than DRAM
instruction set architecture (architecture)
- abstract interface between the hardware and the lowest-level software that encompasses all the information necessary to write a machine language program that will run correctly, including instructions, registers, memory access, I/O, and so on
- most important example of abstraction
application binary interface (ABI)
user portion of the instruction set plus the operating system interfaces used by application programmers. It defines a standard for binary portability across computers
implementation
Hardware that obeys the architecture abstraction
volatile memory
Storage, such as DRAM, that retains data only if it is receiving power
nonvolatile memory
form of memory that retains data even in the absence of a power source and that is used to store programs between runs. A DVD disk is nonvolatile
main memory (primary memory)
memory used to hold programs while they are running; typically consists of DRAM in today’s computers.
secondary memory
nonvolatile memory used to store programs and data between runs; typically consists of flash memory in PMDs and magnetic disks in servers
magnetic disk (hard disk)
form of nonvolatile secondary memory composed of rotating platters coated with a magnetic recording material. Because they are rotating mechanical devices, access times are about 5 to 20 milliseconds and cost per gigabyte in 2012 was $0.05 to $0.10
flash memory
nonvolatile semiconductor memory. It is cheaper and slower than DRAM but more expensive per bit and faster than magnetic disks. Access times are about 5 to 50 microseconds and cost per gigabyte in 2012 was $0.75 to $1.00
transistor
on/off switch controlled by an electric signal
Very large-scale integrated (VLSI) circuit
device containing hundreds of thousands to millions of transistors
wafer
slice from a silicon ingot no more than 0.1 inches thick, used to create chips
defect
microscopic flaw in a wafer or in patterning steps that can result in the failure of the die containing that defect
die
individual rectangular sections that are cut from a wafer, more informally known as chips
yield
percentage of good dies from the total number of dies on the wafer
response time (execution time)
total time required for the computer to complete a task, including disk accesses, memory accesses, I/O activities, operating system overhead, CPU execution time, and so on
throughput (bandwidth)
measure of performance, it is the number of tasks completed per unit time
performance
the inverse of execution time
CPU execution time
- actual time the CPU spends computing for a specific task
- only valid and unimpeachable measure of performance
User CPU time
CPU time spent in a program itself
system CPU time
CPU time spent in the operating system performing tasks on behalf of the program
clock cycle (tick, clock tick, clock period, clock, or cycle)
time for one clock period, usually of the processor clock, which runs at a constant rate
clock period
length of each clock cycle
clock cycles per instruction (CPI)
average number of clock cycles per instruction for a program or program fragment
instruction count
number of instructions executed by the program
instruction mix
measure of the dynamic frequency of instructions across one or many programs
workload
set of programs run on a computer that is either the actual collection of applications run by a user or constructed from real programs to approximate such a mix. A typical workload specifies both the programs and the relative frequencies
benchmark
program selected for use in comparing computer performance
pitfall: improvement is affected by how much time a feature is used
Expecting the improvement of one aspect of a computer to increase overall performance by an amount proportional to the size of the improvement
amdahl’s law
rule stating that the performance enhancement possible with a given improvement is limited by the amount that the improved feature is used. It is a quantitative version of the law of diminishing returns
fallacy: Computers at low utilization use little power
non energy-proportional computing
fallacy: Designing for performance and designing for energy efficiency are unrelated goals
it is often the case that hardware or software optimizations that take less time save energy overall even if the optimization takes a bit more energy when it is used
pitfall: Using a subset of the performance equation as a performance metric
- nearly all proposed alternatives to the use of time as the performance metric have led eventually to misleading claims, distorted results, or incorrect interpretations
- common mistake is to use only two of the three factors to compare performance
million instructions per second (MIPS)
- measurement of program execution speed based on the number of millions of instructions. MIPS is computed as the instruction count divided by the product of the execution time and 106
- MIPS = instruction count/(execution time x 10^6)
- cannot compare computers with different instruction sets using MIPS
- if a new program executes more instructions but each instruction is faster, MIPS can vary independently from performance
- varies between programs on the same computer; thus, a computer cannot have a single MIPS rating
