Computer Science Test 2

Gate

Device that performs basic operation on electrical signals

Circuit

Gates combined to perform more complicated tasks

Boolean Expressions

uses boolean algebra to express two-valued logic

Logic Diagrams

graphical representation of a circuit with gate symbols

Truth tables

table showing all possible input and output values

NOT gate

accepts one input and returns the complementary signal

AND gate

accepts two inputs and outputs 1 only if both are 1

OR gate

accepts two inputs and outputs 1 if at least one is 1

XOR gate

accepts two inputs and outputs 1 if inputs are different

NAND gate

accepts two inputs and outputs 0 if both are 1

NOR gate

accepts two inputs and outputs 1 if both are 0

three-input AND gate

produces output of 1 only if all inputs are 1

transistor

acts are wire or resistor based on input voltage level

collector

terminal of a transistor

base

terminal of a transistor

emitter

terminal of a transistor

combinational circuit

output determined by input values

sequential circuit

output determined by input values and existing state

circuit equivalence

two circuits producing same output for identical input

Boolean Algebra

applies mathematical principles to design circuits

adders

special circuits for binary addition

half adder

computers sum of two bits and produces carry bit

full adder

takes carry-in value into account

Multiplexer(MUX)

routes input data based on input control signals

sequential circuit

circuit that stores information and uses output as input

S-R latch

circuit that stores a single binary digit

Integrated Circuit(IC)

silicon piece with embedded gates or transistors

Central processing unit(CPU)

most important IC in a computer system

NOT Gate

AND gate

OR Gate

XOR Gate

NAND gate

NOR gate

Admiral Grace Murray Hopper

Illustrated sizes in perspective

Coil of wire

Nearly 1,000 feet long

Distance traveled by an electron in a space microsecond

short piece of wire

travels in a space nonsecond

bag of grains of pepper

travels in a space picosecond

Intel Processor

“Faster is better“ applies here. A higher clock speed(GHz) generally indicates better performance for a processor, so a 2.66 GHz processor is better than a slower one

SDRAM

“Bigger is better“ applies to the size(4GB) if you need more memory for your tasks. However, “Faster is better“ also applies to the speed(800 MHz) because a higher memory speed can improve overall system performance

500GB SATA at 5400 RPM

“bigger is better“ applies to the storage size if you need more storage capacity. However “Faster is better“ applies to the transfer rate because a higher transfer rate because a higher transfer rate means faster data access and transfer speeds

Flat screen dot pitch

“smaller is better“ applies here. A smaller dot pitch means that the pixels on the screen are closer together, resulting in a sharper and more detailed display

What is an Intel Processor speed?

2.66 GHz

What is a SDRAM speed?

800 MHz

What is a SDRAM size

4GB

What is an 500 GB SATA at 5400RPM transfer rate?

300 MB per second

What is a Flat screen dot pitch size for pixels?

0.28mm

Memory

collection of cells with unique physical addresses

most computers are byte-addressable

“Little-endian“ bit numbering

Arithmetic/Logic Unit

Performs functions such as addition and subtraction as well as AND, OR, and NOT

Registers

special storage units in ALUs

Input Unit

a device through which data and programs from the outside world enter the computer system

Name 3 Input Units

Keyboard, mouse, microphone

Keyboard

an input unit that allows users to input text and commands into a computer by pressing keys

Mouse

input device that allows users to move a cursor on the screen and interact with graphical user interfaces by clicking icons, buttons, and other elements

Mircophone

an input device that converts sound waves into electrical signals, allowing users to input audio data, such as voice recordings or voice commands into a computer

output unit

a device through which results stored in the computer memory are made available outside the computer system

Name 2 output units

monitor and printer

Monitor

an output unit that displays visual information including text, images, videos, and user interfaces to the user. it provides a visual representation of the computers output

Printer

output device that produces physical copies of digital documents, images, or other content. converts electronic data into a printed form on paper or other media

control unit

organizing force int he computer

Instruction Register(IR)

contains the executing instruction

Program Counter(PC)

contains the address of the next instruction

Central Processing Unit(CPU)

ALU and control unit

Bus

communication system transferring data between components

What does “bus“ connect?

connection between CPU, memory, I/O devices, and possibly other components(hard disk drive)

what is an N-bit processor?

this could refer to registers, ALU, addresses, or data bus

Fetch-Execute Cycle

fetch the next instruction

decode the instruction

get data if needed

execute the instruction

store the result of the instruction in memory

Why is it called a cycle?

it represents a repetitive and continuous sequence of operations that a computer’s central processing unit performs to execute instructions stored in memory

Random Access Memory(RAM)

each location can be accessed and changed; is volatile

Read Only Memory(ROM)

each location can be accessed but not changed; is not volatile

What does volatile mean?

the characteristic of the memory where data stored in RAM is temporary and is lost when the power to the computer is turned off or when the system is restarted

Why is it necessary to have secondary storage devices?

by providing persistent, high-capacity storage for data, software, and backups

Examples of secondary storage devices

Hard Disk Drive, Solid-State Drive, USB Flash Drive, External Hard Drive

Hard Disk Drive

one of the most common types of secondary storage devices. They provide high-capacity storage using spinning magnetic disks to store data. are found in desktop and laptop computers as well as external drives

Solid-State Drive

uses flash memory to store data. They are faster and more durable than HDDs but typically offer less storage capacity. are commonly used in laptops and desktops, and they are also available as external drives

USB Flash Drive

are portable secondary storage devices that connect to a computer's USB port. They are small, lightweight, and offer a convenient way to transfer and store data

External Hard Drive

connects to a computer via USB, Thunderbolt, or other interfaces. they are commonly used for backup, storage expansion, and data transfer

Magnetic Tape

first mass auxiliary storage device

The major problems with tape drivers

slow access speed, physical tape damage, limited random access, obsolete technology data deregulation

Magnetic Disks Access time

typically ranges from 2 to 15 milliseconds

seek time

time to read/write

latency

time for the second to be in position

transfer rate

rate at which data moves from the disk to memory

Optical Disks

CD, DVD, Blu-ray

CD

compact disk with laser reading

CD-ROM

CD read-only memory

CD-DA

CD digital audio

CD-WORM

CD write once, read many

RW or RAM

both read from and written to

DVD

Digital Versatile Disk, used for storing audio and video

Blu-ray

higher capacity DVD allowing higher resolution video, etc.

Flash Memory

nonvolatile, can be erased and rewritten

supports USB. mass storage standard

Touch screen

a computer monitor that responds to the touch of a finger or stylus

Resistive touch screen

two layer of conductive material, touch location determined by contact

capacitive touch screen

laminate conducts electricity, touch location determined by comparing current flow

Infrared touch screen

horizontal and vertical beams of infrared light, touch location determined by beam break

Surface Acoustic Wave(SAW)

high-frequency sound waves, touch location determined. by interruption

embedded systems

computers dedicated to perform specific functions

parallel computing

four forms: bit-level, instruction-level, data-level, task-level