Computers are made up of two main categories: hardware and software.
Hardware = the physical components installed inside or connected to a computer system.
Software = instructions or data stored electronically (on a hard drive or on a special chip) that tell the hardware what to do.
Key takeaway: hardware = potential; software = instructions that unlock that potential.
Input devices
Input device = any hardware that takes information from outside the computer and transfers it inside where the computer hardware can use it.
Keyboard
Most common input device.
When a key is pressed, an internal scanning chip identifies which key was pressed and sends the appropriate code to the computer.
The code can generate a letter in a word document, a number in a spreadsheet, or a command for the computer.
Mouse
Tracks movements as x, y coordinates and sends signals to the computer.
Movement tracking depends on the type of mouse: optical vs mechanical.
Optical mouse: uses a light source and a sensor to track movement.
Mechanical mouse: uses a trackball that rolls; sensors identify direction of the ball.
Touchscreen
Input from screen tabs; common on smartphones, tablets, and kiosks.
Two main technologies: resistive and capacitive.
Resistive touchscreens:
Use two flexible layers separated by a gap containing an electrical current.
When tapped, outer layer depresses and contacts the inner layer, creating an electrical signal that gives x, y coordinates.
Capacitive touchscreens:
Screen coated with conductive material; electrical current runs through material.
When something conductive (like a finger) touches the screen, sensors identify the touch and generate x, y coordinates.
Used on smartphones, tablets, and some laptops.
Limitation: require a conductive touch; nonconductive objects (gloves, plastic) cannot be used.
Use cases:
Resistive screens: often used in airport or library kiosks because they can be activated with any rigid object or pressure.
Capacitive screens: common in consumer devices but require conductive touch.
Signals from input devices
All input signals are analyzed by a processing device to interpret the information.
Processing devices
Processing device = hardware that analyzes and interprets input information.
Central Processing Unit (CPU)
The brains of the computer.
Processes data according to the software currently running.
Example:
Word processing software: pressing a key makes the letter appear at the cursor location in the document.
A game: the same key could move a character left.
RAM (Random Access Memory)
Used to store processed information for quick access later.
Also used to store running software.
RAM is a type of storage device (per the transcript’s wording) used for short-term storage during operation.
RAM is volatile memory: when power is lost, data in RAM is lost.
Statement in the transcript: RAM is used to store data temporarily for fast access after processing.
Summary point: processing devices = CPU + RAM (and other devices can exist, but these are the core examples given).
Storage devices
Storage device = hardware that stores data temporarily or permanently.
Short-term storage (volatile)
RAM is used for temporary storage of data being processed and for storing running software.
Volatile memory means when power is turned off, data in RAM is lost: D_{ ext{RAM}}(P= ext{off}) = \emptyset
Long-term storage (nonvolatile, persistent)
Data remains even when power is off.
Common long-term storage media:
Hard disk drive (HDD): stores data on rotating disks called platters.
Solid-state drive (SSD): uses memory chips; data is persistent.
Both HDDs and SSDs store large amounts of data and offer relatively fast access, but RAM is faster than both.
Optical storage media: CDs, DVDs, and Blu-ray discs (BDs or BRDs).
Read-only (ROM): information is fixed and cannot be modified or erased; examples include software CD-ROM or DVD-ROM. ROM stands for Read-Only Memory.
Writable discs (recordable): can have information saved to them; examples include CDR, DVD-R, DVD-RW, BD-R, BD-RW.
Additional long-term storage devices:
Flash drives: small portable devices using memory chips; data is persistent.
SD (Secure Digital) cards: used in smartphones, tablets, and digital cameras; nonvolatile memory.
Why use RAM and long-term storage together?
RAM provides extremely fast access to data during active processing.
Long-term storage holds data persistently for future use.
Optical storage details (ROM vs RW)
ROM = Read-Only Memory; read-only discs cannot be modified.
Writable discs include:
CD-R, DVD-R, BD-R (R = Recordable)
DVD-RW, BD-RW (RW = Rewritable)
Access characteristics:
ROM: data fixed at manufacture; no changes.
RW: data can be added/modified after manufacture.
Output devices
Output device = any device that receives data from a computer and presents it in a physical medium.
Monitor (display): visually depicts processed data (e.g., numbers in a spreadsheet or graphics in a game).
Printer: prints processed information onto paper.
Sound card: converts digital information into audible signals (audio output).
Summary: all the devices discussed so far communicate information within a single computer via input, processing, and storage chains, culminating in output.
Networking devices
Networking devices enable communication between multiple computers.
A network = group of two or more connected computers.
To create a network:
A network interface is installed in each computer.
A connecting medium is used to connect computers together.
Connecting mediums can be physical wires or radio signals (wireless).
Networking devices are both input and output devices in practice:
When one computer outputs information, another can input it, and vice versa.
Modular design
Modular design = design approach that standardizes hardware interfaces to create modular hardware components.
Benefits:
Components from different manufacturers can work together (interchangeability).
Historical context:
Early computers often used proprietary hardware; replacements required sending components back to the manufacturer.
Modern implication:
You can install a different brand hard drive or other component and have it work with the system.
Example:
If you want to install another hard disk drive, any brand will work with the computer, thanks to modular and standardized interfaces.
Five main functions of computer hardware (as described in the lesson)
Input: devices like keyboard, mouse, touchscreen gather information from the user and environment.
Processing: CPU and RAM process and manage data according to software.
Storage: RAM for short-term storage; HDD/SSD/optical/flash/SD for long-term storage.
Output: monitor, printer, sound card, and other devices that present data to the user.
Networking: enables communication between multiple computers and sharing of resources.
Connections to broader concepts
Foundational principles:
Hardware provides potential; software provides instructions to realize that potential.
Data flows: input -> processing -> storage (temporary or permanent) -> output.
Networking expands the reach of a computer beyond a single device.
Real-world relevance:
Understanding input devices helps in selecting peripherals and diagnosing input issues.
Knowledge of RAM vs. storage informs performance considerations and upgrade decisions.
Modular design enables easier upgrades and compatibility across brands.
Ethical/philosophical/practical implications:
Modular designs promote consumer choice and reduce vendor lock-in.
Ownership and upgradability impact sustainability and e-waste considerations.
Recap of the five main hardware functions:
Input, Processing, Storage, Output, Networking.
Core takeaway:
Remember the two main computer component categories: hardware and software. Hardware = potential; Software =