CS250 Midterm 1 Vocab

CS250 Computer Architecture @ Purdue

Personal computer

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 program 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

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

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

A microprocessor containing multiple processors (“cores”) in a single integrated circuit.

Acronym

A word constructed by taking the initial letters of a string of words. For example: RAM is a(n) ____ for Random Access Memory, and CPU is a(n) ____ for Central Processing Unit.

Terabyte

Originally 1,099,511,627,776 (2⁴⁰) bytes, although communications and secondary storage system developers started using the term to mean 1,000,000,000,000 (10¹²) bytes.

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

A program that translates high-level language statements into assembly language statements.

Binary digit

Also called a bit. One of the two numbers in base 2 (0 or 1) that are the components of information.

Instruction

A command that computer hardware understands and obeys.

Assembler

A program that translates a symbolic version of instructions into the binary version.

Assembly language

A symbolic representation of machine instructions.

Machine language

A binary representation of machine instructions.

High-level programming language

A 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

A mechanism through which the computer is fed information, such as a keyboard.

Output device

A mechanism that conveys the result of a computation to a user, such as a display, or to another computer.

Liquid crystal display

A 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

A liquid crystal display using a transistor to control the transmission of light at each individual pixel

Pixel

The smallest individual picture element. Screens are composed of hundreds of thousands to millions of ____s, organized in a matrix.

Integrated circuit

Also called a chip. A device combining dozens to millions of transistors.

Central processor unit

Also called processor. The active parts 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

The component of the processor that performs arithmetic operations.

Control

The component of the processor that commands the datapath, memory, and I/O devices according to the instructions of the program.

Memory

The storage area in which programs are kept when they are running and that contains the data needed by running programs.

Dynamic random access memory

Memory built as an integrated circuit; it provides random access to any location. Access times are 50 nanoseconds and cost per gigabyte in 2020 was $3 to $6.

Cache memory

A small, fast memory that acts as a buffer for a slower, larger memory.

Static random access memory

Also memory built as an integrated circuit, but faster and less dense than DRAM

Instruction set architecture

Also called architecture. An 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.

Application binary interface

The 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 its receiving power.

Nonvolatile memory

A 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

Also called 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

Also called hard disk. A form of nonvolatile secondary memory composed of rotating patters 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 2020 was $0.01 to $0.02.

Flash memory

A 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 2020 was $0.06 to $0.12.

Local area network

A network designed to carry data within a geographically confined area, typically within a single building.

Wide area network

A network extended over hundreds of kilometers that can span a continent.

Transistor

An on.off switch controlled by an electric signal.

Very large-scale integrated circuit

A device containing hundreds of thousands to millions of transistors.

Silicon

A natural element that is a semiconductor.

Semiconductor

A substance that does not conduct electricity well

Silicon crystal ingot

A rod composed of a silicon crystal that is between 8 and 12 inches in diameter and about 12 to 24 inches long.

Wafer

A slice from a silicon ingot no more than 0.1 inches thick, used to create chips.

Defect

A microscopic flaw in a wafer or in patterning steps that can result in the failure of the die containing that defect.

Die

The individual rectangular sections that are cut from a wafer, more informally known as chips.

Yield

The percentage of good dies from the total number of dies on the wafer.

Response time

Also called execution time. The total time required

Throughput

Also called bandwidth. Another measure of performance, it is the number of tasks completed per unit time.

CPU execution time

Also called CPU time. The actual time the CPU spends computing for a specific task.

User CPU time

The CPU time spent in a program itself.

System CPU time

The CPU time spent in the operating system performing tasks on behalf of the program.

Clock cycle

Also called tick, clock tick, clock period, clock, or cycle. The time for one clock period, usually of the processor clock, which runs at a constant rate.

Clock period

The length of each clock cycle

Clock cycle per instruction

Average number of clock cycles per instruction for a program or program fragment.

Instruction count

The number of instructions executed by the program.

Instruction mix

A measure of the dynamic frequency of instructions across one or many programs.

Amdahl’s Law

A 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.

Million instructions per second

A measurement of program execution speed based on the number of millions of instructions. ____ is computed as the instruction count divided by the product of the execution time and 10⁶.

Instruction set

The vocabulary of commands understood by a given architecture.

Stored-program concept

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.

Word

A 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.

Data transfer instruction

A command that moves data between memory and registers.

Address

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

Alignment restriction

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

Binary digit

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

Least significant bit

The rightmost bit in an LEGv8 doubleword.

Most significant bit

The leftmost bit in an LEVv8 doubleword.

Two’s complement

A 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

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.

Biased notation

A notation that represents the most negative value by 00…000_two and the most positive value by 11.11_two, 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.

Instruction format

A 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.

Opcode

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

OR

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

NOT

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.

EOR

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.

Conditional branch

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.

Basic block

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

Branch address table

Also called branch table. A table of addresses of alternative instruction sequences.

Arithmetic Logic Unit

Hardware that performs addition, subtraction, and usually logical operations such as AND and OR.