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A+ Core 1 220-1201 cheat sheet

Every exam tip and key term from the free A+ Core 1 lessons, by domain. Use your browser's Print to save it as a PDF.

Domain 1: Mobile devices (13%)

Exam tips

A part that fits is not always a part that works: an M.2 SATA drive in an NVMe-only slot or DDR5 in a DDR4 board will fail. Soldered RAM means no upgrade path.
Dim image visible with a flashlight means backlight (or inverter on CCFL). OLED has no backlight, so that diagnosis does not apply. Good image with bad touch points to the digitizer.
Match the control to the threat: shoulder surfing means privacy screen; laptop stolen from a desk means cable lock; lost device data means encryption plus remote wipe; convenient sign-in means biometrics with a PIN fallback.
USB-C is a connector shape, not a guarantee of features. Questions often hinge on a port or cable that does not support video, charging or Thunderbolt. Lightning is Apple-only; micro-USB is the older non-reversible one.
When an accessory seems dead, check the simple things first: power or battery, pairing, a function-key toggle, privacy settings and whether the correct device is selected in the OS or app.
Match the technology to the scenario: accessories use Bluetooth, tap-to-pay and badges use NFC, sharing a phone's cellular connection is tethering or a hotspot, and fast local network access is Wi-Fi.
Airplane mode kills all transmitting radios, but Wi-Fi and Bluetooth can be turned back on individually. eSIM is embedded and provisioned by QR code or app. IMEI identifies the device; IMSI identifies the subscriber.
GPS is accurate but needs a sky view and is receive-only. Cellular location works indoors but is coarse. Per-app location permissions are the privacy control the exam expects you to recommend.
Full wipe for corporate devices; selective or enterprise wipe for BYOD. MAM protects apps and data without controlling the whole device, which suits personal phones.
For multiple devices, choose IMAP or an Exchange-style account, not POP3. Authenticator apps are stronger than SMS codes, but they must be migrated before a phone is wiped.

Key terms

SODIMM: Small outline dual inline memory module, the short memory module used in laptops and small form factor PCs.
Soldered RAM: Memory permanently attached to the motherboard that cannot be upgraded or replaced separately.
M.2: A small card form factor for SSDs and wireless cards that can carry SATA or PCIe signals depending on the slot.
NVMe: Non-Volatile Memory Express, a storage protocol that runs over PCIe lanes and is much faster than SATA.
B+M key: An M.2 edge with two notches, typical of M.2 SATA SSDs.
ZIF connector: Zero insertion force connector with a latch that clamps a flat ribbon cable.
Antenna leads: Thin coaxial cables that connect the wireless card to antennas in the display bezel.
LCD: Liquid crystal display, a panel that uses crystals as light shutters and needs a separate backlight.
OLED: Organic light-emitting diode display in which each pixel emits its own light, so no backlight is needed.
Backlight: The light source behind an LCD panel, usually LEDs in modern screens.
Inverter: A board in older CCFL-backlit laptops that supplies high-voltage power to the fluorescent lamp.
Digitizer: The touch-sensing layer that converts finger or pen contact into screen coordinates.
Bezel: The frame around the display that holds the webcam, microphones and wireless antennas.
Burn-in: A permanent faint ghost image on an OLED screen caused by long display of static content.
Biometrics: Authentication based on a physical trait such as a fingerprint or face.
Windows Hello: The Windows feature that allows sign-in with face, fingerprint or a device PIN.
Privacy screen: A filter or built-in mode that narrows a display's viewing angle so people to the side cannot read it.
Shoulder surfing: Watching someone's screen or keyboard to steal information or credentials.
NFC: Near-field communication, a radio that works over a few centimeters for payments, badges and security keys.
Cable lock: A steel cable that secures a laptop to furniture through its security slot.
Full-disk encryption: Encryption of an entire drive so data is unreadable without the key if the device is stolen.
USB-C: A small, reversible connector that can carry USB data, power delivery, video and Thunderbolt depending on the port.
USB Power Delivery: A USB charging standard that negotiates higher power levels over USB-C.
Alternate mode: A USB-C feature that sends non-USB signals such as DisplayPort video over the connector.
Lightning: Apple's proprietary 8-pin reversible connector used on many iPhones and accessories.
Micro-USB: An older, small, non-reversible connector common on earlier Android phones and small gadgets.
Docking station: A device that gives a laptop power, video, network and many ports through one connection.
Port replicator: A simpler device that duplicates a laptop's ports without the extras of a full dock.
Passive stylus: A capacitive pen that mimics a fingertip and needs no power or pairing.
Active stylus: A powered pen that talks to a compatible digitizer for pressure sensitivity, palm rejection and buttons.
Default audio device: The output or input the operating system uses unless an app chooses another.
UVC: USB Video Class, a standard driver model that lets most USB webcams work without extra software.
Trackpad: The touch-sensitive pointing surface on a laptop, also called a touchpad.
Palm rejection: A feature that ignores accidental contact from the hand while typing or writing.
Drawing pad: An external pressure-sensitive tablet used with a pen, usually needing a vendor driver.
Pairing: The one-time process of linking two Bluetooth devices so they trust and reconnect to each other.
Discoverable mode: A state in which a Bluetooth device advertises itself so another device can find and pair with it.
Hotspot: A phone acting as a Wi-Fi access point to share its cellular data connection.
Tethering: Sharing a phone's cellular connection with another device over Wi-Fi, USB or Bluetooth.
SSID: Service set identifier, the name of a Wi-Fi network.
MAC randomization: A privacy feature that makes a device use a different hardware address on each Wi-Fi network.
LTE: Long Term Evolution, the technology behind most 4G cellular service.
5G: The newer cellular generation with higher potential speed, lower latency and more device capacity.
Airplane mode: A setting that turns off all transmitting radios at once; Wi-Fi and Bluetooth can usually be re-enabled individually.
Data roaming: Using another carrier's network outside your home area, often at extra cost.
SIM: Subscriber identity module, a removable card that identifies the subscriber to the carrier.
eSIM: An embedded SIM built into the device and provisioned with a carrier profile by QR code or app.
IMEI: International Mobile Equipment Identity, a unique number that identifies the phone hardware.
IMSI: International Mobile Subscriber Identity, the subscriber identifier stored on the SIM or eSIM profile.
GPS: Global Positioning System, a receive-only satellite system that calculates position from signal timing.
GNSS: Global navigation satellite system, the general name for GPS and similar satellite positioning systems.
Trilateration: Working out a position from the distances to several known points, such as satellites.
Cellular location: An approximate position estimated from the cell towers a phone can hear.
Wi-Fi positioning: Estimating location by matching nearby Wi-Fi networks against a database of known locations.
A-GPS: Assisted GPS, which downloads satellite data over a network to get a faster first fix.
Location permission: A per-app setting that controls whether and when an app may read the device's location.
MDM: Mobile device management, centralized control of whole devices, including settings, apps and wipe.
MAM: Mobile application management, protecting and controlling only managed work apps and their data.
Enrollment: The process of bringing a device under management, which installs a management profile.
BYOD: Bring your own device, a program that lets employees use personal devices for work.
Compliance policy: Rules a device must meet, such as encryption and OS version, before it may access company resources.
Full wipe: A remote reset that erases everything and returns the device to factory settings.
Selective wipe: A remote action that removes only corporate apps, accounts and data, also called an enterprise wipe.
IMAP: Internet Message Access Protocol, which keeps mail on the server and syncs it across devices.
POP3: Post Office Protocol version 3, which downloads mail to one device and may remove it from the server.
Exchange ActiveSync: A Microsoft protocol that syncs mail, calendar, contacts and tasks and can apply device policies.
CalDAV and CardDAV: Standard protocols for syncing calendars and contacts.
Cloud sync: A service that keeps files, photos and backups in online storage and synchronizes them across devices.
TOTP: Time-based one-time password, a short code that changes every few seconds and is generated by an authenticator app.
SIM swapping: Fraud in which an attacker gets a victim's phone number moved to another SIM to receive their SMS codes.

Domain 2: Networking (23%)

Exam tips

Pair secure and insecure versions: Telnet 23 vs SSH 22, HTTP 80 vs HTTPS 443. DHCP and SNMP use UDP; DNS is mostly UDP but also TCP. SMB is 445 and RDP is 3389.
Router means between networks (IP); switch means within a network (MAC). Managed switch equals VLAN support. A PoE injector powers one device when the switch cannot. ONT means fiber, cable modem means coax, DSL means phone line.
Memorize the band per standard: a is 5 GHz, b and g are 2.4 GHz, n is both, ac is 5 GHz, ax is 2.4 and 5 GHz plus 6 GHz as Wi-Fi 6E. 2.4 GHz means longer range but more interference; 5 and 6 GHz mean more speed but shorter range.
Match the symptom to the service: names fail but IPs work means DNS; 169.254 addresses mean DHCP; central Wi-Fi logins mean RADIUS; many security features in one box means UTM; spreading load across servers means load balancer.
Port forwarding needs a fixed internal address, so pair it with a static IP or DHCP reservation. Prefer port forwarding over the SOHO DMZ host setting. Choose WPA3, or WPA2 with AES, and disable WPS and UPnP.
169.254.x.x means the client could not reach DHCP. Memorize the three private ranges, especially that 172.16 to 172.31 is private but 172.32 is not. Local works but remote fails means gateway; IPs work but names fail means DNS.
A is IPv4, AAAA is IPv6, CNAME is an alias to another name, MX is mail with the lowest priority number preferred. SPF, DKIM and DMARC are all TXT records. VLANs separate traffic on switches; VPNs encrypt traffic across the internet.
High latency is the classic weakness of traditional geostationary satellite. DSL slows with distance. Cable is shared with neighbors. Fixed wireless needs line of sight to a tower. Fiber is fastest and most reliable where available.
Scale clues decide the answer: person, building, city, country. SAN is the odd one out because it is about storage, not distance, and it gives servers block storage, unlike file-sharing NAS.
Crimper for plugs on cable ends, punchdown for patch panels and jacks, toner probe to find a cable, cable tester to verify wiring, loopback plug to test a port by itself, Wi-Fi analyzer for channels and signal.

Key terms

TCP: Transmission Control Protocol, a connection-oriented transport with handshakes, acknowledgments and retransmission.
UDP: User Datagram Protocol, a connectionless transport that is fast but does not guarantee delivery.
Three-way handshake: The SYN, SYN-ACK, ACK exchange TCP uses to open a connection.
Port number: A number that identifies a specific service or application on a host.
SSH: Secure Shell, encrypted remote command-line access on TCP 22.
SMB: Server Message Block, Windows file and printer sharing on TCP 445.
RDP: Remote Desktop Protocol, graphical remote access to Windows on TCP 3389.
SNMP trap: An unsolicited alert a managed device sends to a management station on UDP 162.
Router: A Layer 3 device that forwards packets between different networks using IP addresses.
Switch: A Layer 2 device that forwards frames within a LAN using MAC addresses.
Managed switch: A configurable switch that supports features such as VLANs, port security and monitoring.
Access point: A device that connects wireless clients to the wired network.
Patch panel: A passive rack panel where in-wall cables terminate and patch cables connect to switches.
PoE injector: A device that adds Power over Ethernet to a single cable when the switch cannot supply power.
ONT: Optical network terminal, the device that converts a fiber connection to Ethernet at the customer premises.
802.11: The IEEE family of standards that defines Wi-Fi.
Non-overlapping channels: Channels that do not share frequencies; on 2.4 GHz these are 1, 6 and 11 in most regions.
Channel bonding: Combining adjacent channels into a wider channel for more throughput.
DFS: Dynamic frequency selection, which moves 5 GHz Wi-Fi off channels where radar is detected.
MIMO: Multiple input, multiple output, using several antennas at once to increase throughput.
OFDMA: A Wi-Fi 6 technique that splits a channel so one transmission can serve several clients.
RFID: Radio-frequency identification, which reads tags wirelessly for tracking and access.
DNS server: A server that resolves hostnames to IP addresses.
DHCP server: A server that automatically assigns IP addresses and related settings to clients.
Syslog: A standard for sending log messages to a central collector.
AAA: Authentication, authorization and accounting, the framework for controlling and recording access.
RADIUS: Remote Authentication Dial-In User Service, a protocol that centralizes authentication for networks and VPNs.
Proxy server: A server that makes web requests on behalf of clients and can cache, filter and log them.
UTM: Unified threat management, one appliance combining firewall, intrusion prevention, antivirus, filtering and VPN.
Load balancer: A device that distributes incoming requests across multiple servers and skips unhealthy ones.
DHCP scope: The range of IP addresses a DHCP server can hand out.
DHCP reservation: A setting that always gives the same IP address to a device based on its MAC address.
NAT: Network address translation, which lets many private addresses share one public address.
Port forwarding: A rule that sends inbound traffic on a specific port to a specific internal host.
DMZ host: A SOHO router setting that forwards all unsolicited inbound traffic to one internal device.
Screened subnet: A separate, firewalled network segment for public-facing servers.
UPnP: Universal Plug and Play, which lets devices open router port forwards automatically.
SAE: Simultaneous Authentication of Equals, the WPA3 Personal handshake that resists offline password guessing.
IPv4: A 32-bit address written as four decimal numbers separated by dots.
IPv6: A 128-bit address written as eight groups of hexadecimal digits separated by colons.
Private address: An address from 10.0.0.0/8, 172.16.0.0/12 or 192.168.0.0/16 that is not routed on the internet.
APIPA: Automatic Private IP Addressing, a 169.254.x.x address Windows assigns itself when DHCP fails.
Subnet mask: A value that separates the network portion of an address from the host portion.
Default gateway: The local router address that a device sends traffic to for other networks.
Link-local address: An IPv6 address starting with fe80 that works only on the local segment.
A record: A DNS record that maps a hostname to an IPv4 address.
AAAA record: A DNS record that maps a hostname to an IPv6 address.
CNAME record: A DNS alias that points one name to another name.
MX record: A DNS record naming the mail servers for a domain, with the lowest priority number preferred.
SPF: Sender Policy Framework, a TXT record listing servers allowed to send mail for a domain.
DKIM: DomainKeys Identified Mail, which signs messages and publishes the verification key in a TXT record.
DMARC: A TXT record that sets the policy and reporting for mail that fails SPF and DKIM alignment.
VLAN: A virtual LAN that logically separates devices on shared switch hardware.
Latency: The delay for data to travel to its destination and back.
Fiber: Internet service that carries data as light through glass strands, offering high, often symmetrical speeds.
Cable internet: Internet delivered over the coaxial cable TV network using a cable modem.
DSL: Digital subscriber line, internet over telephone copper whose speed drops with distance.
Geostationary satellite: A satellite in very high orbit that stays over one spot, causing high latency.
LEO satellite: A low Earth orbit satellite in a large constellation that provides lower-latency service.
WISP: Wireless internet service provider, delivering fixed wireless service to a directional antenna with line of sight.
PAN: Personal area network, the devices around one person, such as Bluetooth accessories.
LAN: Local area network, devices within one building or site.
WLAN: Wireless LAN, the part of a LAN connected by Wi-Fi.
MAN: Metropolitan area network, linking sites across a city or large campus.
WAN: Wide area network, connecting networks across regions, countries or continents.
SAN: Storage area network, a dedicated network giving servers block-level access to shared storage.
NAS: Network-attached storage, a device on the LAN that shares files with users.
Crimper: A tool that attaches a connector such as RJ45 to the end of a cable.
Cable stripper: A tool that removes cable jacket and insulation without damaging the conductors.
Punchdown tool: A tool that seats and trims wires in patch panels, keystone jacks and 110 blocks.
Toner probe: A tone generator and probe used to locate a specific cable in a bundle.
Cable tester: A device that checks continuity and wiring order, finding opens, shorts and crossed pairs.
Loopback plug: A plug that connects a port's transmit to its receive so the port can test itself.
Wi-Fi analyzer: A tool that shows wireless networks, channels, signal strength and interference.
Network tap: An inline device that copies all traffic on a link to a monitoring port.

Domain 3: Hardware (25%)

Exam tips

TN is fastest and cheapest, IPS has the best color and viewing angles, VA has the best contrast among LCDs. OLED has no backlight and can burn in. Mini-LED is a better LCD backlight with local dimming. Always run native resolution.
VGA is the only analog-only video connector in the list. Cat 6 carries 10 Gbps only to about 55 meters; Cat 6a reaches 100 meters. Plenum is required in air-handling spaces. Thunderbolt uses the USB-C shape, but not every USB-C port is Thunderbolt.
DDR generations, and DIMM versus SODIMM, are never interchangeable. Dual channel needs matched modules in the correct slots. ECC needs board and CPU support. Heavy paging-file use is a sign to add physical RAM.
Know minimum drives and fault tolerance: RAID 0 (2, none), RAID 1 (2, one), RAID 5 (3, one), RAID 6 (4, two), RAID 10 (4, one per mirrored pair). RAID is not a backup.
Size order from large to small is ATX, microATX, Mini-ITX, and smaller boards fit bigger cases. Graphics cards go in PCIe x16. LGA puts the pins in the socket, PGA puts them on the CPU. A newer CPU on an older board may need a firmware update first.
Match the symptom to the setting: VM will not start means VT-x or AMD-V; cannot boot from USB means boot order; Windows 11 blocked means TPM 2.0 or Secure Boot; clock resets mean the CMOS battery. A TPM protects one computer's keys; an HSM protects many keys for an organization.
A 32-bit OS cannot run 64-bit software. ARM needs native or emulated apps. Threads are logical, cores are physical. Always apply fresh thermal paste when reinstalling a heat sink, and treat shutdowns under load as a cooling problem first.
After adding a graphics card, plug the monitor into the card, not the motherboard. Check PSU wattage and PCIe power connectors for power-hungry GPUs. Capture cards bring video in; graphics cards send video out. Always confirm in Device Manager and install drivers.
12 V powers the big consumers; 3.3 V and 5 V power board logic, memory and USB. Check the manual voltage switch on older PSUs when changing countries. Redundant PSUs are for servers and are hot-swappable. Never open a PSU; replace it.
Garbled output points to the wrong driver. A printer asking for different paper points to tray settings. Confidential documents left on the tray point to secure print. Give network printers a static IP or reservation so they do not move.
Memorize the laser order: processing, charging, exposing, developing, transferring, fusing, cleaning. Carbon or multipart forms always mean an impact printer. Direct thermal needs special paper and fades; thermal transfer uses a ribbon and lasts.

Key terms

TN: Twisted nematic, a fast and inexpensive LCD panel with narrow viewing angles and weaker color.
IPS: In-plane switching, an LCD panel with the best color accuracy and wide viewing angles.
VA: Vertical alignment, an LCD panel with strong contrast that sits between TN and IPS.
Mini-LED: An LCD backlight made of many tiny LEDs in local dimming zones for higher contrast.
Native resolution: The physical pixel grid of a panel, which gives the sharpest image.
Refresh rate: How many times per second a display redraws the image, measured in hertz.
Color gamut: The range of colors a display can reproduce, measured against standards such as sRGB or DCI-P3.
Nit: A unit of brightness equal to one candela per square meter.
Thunderbolt: A high-speed interface for data, video and power that uses the USB-C connector in modern versions.
DisplayPort: A digital video and audio interface common on PCs that supports daisy-chaining with MST.
VGA: Video Graphics Array, a blue 15-pin analog-only video connector.
Cat 6a: Twisted pair cable that supports 10 Gbps up to 100 meters.
T568A and T568B: The two wiring standards for RJ45; the same on both ends makes a straight-through cable.
Plenum cable: Fire-resistant, low-smoke cable required in air-handling spaces.
Single-mode fiber: Fiber that uses a laser and a narrow core for very long distances.
Active adapter: An adapter with electronics that converts signals, such as digital to analog VGA.
DDR: Double data rate, memory that transfers data twice per clock cycle.
DIMM: Dual inline memory module, the full-length memory stick used in desktops.
SODIMM: Small outline DIMM, the shorter module used in laptops and small form factor PCs.
Dual channel: A mode in which two matched modules in the correct slots are accessed in parallel for more bandwidth.
ECC memory: Error-correcting code memory that detects and corrects single-bit errors, requiring board and CPU support.
Paging file: The Windows file on disk used as virtual memory when physical RAM runs low.
Virtual memory: Storage space the operating system uses as an extension of RAM.
RPM: Revolutions per minute, the spin speed of an HDD's platters.
NVMe: Non-Volatile Memory Express, a fast SSD protocol that runs over PCIe lanes.
M key: An M.2 notch position used by PCIe x4 NVMe drives.
B key: An M.2 notch position used for SATA and PCIe x2 devices; SATA drives often have B and M notches.
RAID 5: Striping with distributed parity across at least three drives, surviving one failure.
RAID 6: Striping with double parity across at least four drives, surviving two failures.
RAID 10: Mirrored pairs striped together, needing at least four drives and using half the capacity.
SDXC: A high-capacity SD card class that requires a reader supporting it.
ATX: Advanced Technology eXtended, the full-size motherboard form factor with up to seven expansion slots.
microATX: A smaller square form factor with up to four expansion slots that fits most ATX cases.
Mini-ITX: A compact motherboard form factor, typically with one expansion slot and two memory slots, for small PCs.
PCIe: Peripheral Component Interconnect Express, the serial expansion bus whose slots come in x1, x4, x8 and x16 lane widths.
LGA: Land grid array, a socket design where the pins are in the socket and the CPU has flat pads.
PGA: Pin grid array, a socket design where the pins are on the CPU and fit into holes in the socket.
Front-panel header: Motherboard pins that connect the case's power button, reset button and indicator LEDs.
Standoff: A raised spacer that holds the motherboard off the metal case so it cannot short circuit.
UEFI: Unified Extensible Firmware Interface, the modern replacement for BIOS that supports GPT drives and Secure Boot.
POST: Power-on self-test, the firmware's hardware check that runs each time the computer starts.
Secure Boot: A UEFI feature that allows only signed, trusted boot loaders and drivers to run at startup.
TPM: Trusted Platform Module, a secure crypto processor in one computer that stores keys and supports features like BitLocker.
HSM: Hardware security module, a dedicated device for generating and protecting cryptographic keys at scale.
Boot order: The sequence of devices the firmware tries when looking for an operating system to start.
CMOS battery: A small coin-cell battery that keeps the firmware clock and settings when the PC is unplugged.
x64: The 64-bit extension of the x86 architecture used by Intel and AMD processors, also called x86-64 or AMD64.
ARM: A power-efficient RISC processor architecture used in phones, tablets and many modern laptops.
Core: An independent physical processing unit inside a CPU.
Hyper-Threading: Intel's technology that lets one physical core run two threads; AMD's equivalent is SMT.
Integrated graphics: A graphics processor built into the CPU that shares system memory.
Thermal paste: A compound that fills microscopic gaps between a CPU and heat sink to improve heat transfer.
Thermal throttling: A CPU automatically lowering its speed to reduce heat when it gets too hot.
GPU: Graphics processing unit, the processor on a graphics card that renders images and handles parallel workloads.
Capture card: A card or external device that records or streams video from an external source into the PC.
Sound card: An expansion card that provides higher-quality or additional audio inputs and outputs.
NIC: Network interface card, which connects a computer to a wired or wireless network.
PCIe power connector: An extra power cable from the PSU, such as 6-pin or 8-pin, used by high-power graphics cards.
SFP: Small form-factor pluggable, a module slot on some NICs that accepts fiber or copper transceivers.
PSU: Power supply unit, which converts AC wall power into the DC voltages a computer uses.
Auto-switching PSU: A power supply that automatically accepts input voltages across the 110 to 240 V range.
12 V rail: The PSU output that powers the CPU, graphics card, fans and drive motors.
24-pin ATX connector: The main power connector from the PSU to the motherboard.
Modular PSU: A power supply whose cables can be detached so only needed cables are installed.
Redundant power supply: Two or more hot-swappable PSUs in one system so it keeps running if one fails.
Wattage rating: The maximum continuous power a PSU can deliver to components.
Multifunction device: A device that combines printing, scanning, copying and often faxing.
Print driver: Software that translates application output into a language the printer understands, such as PCL or PostScript.
Duplex: Printing on both sides of the paper, automatically or with manual flipping.
Tray settings: Configuration that tells the printer what paper size and type are loaded in each tray.
Print server: A server that shares printers, manages queues and distributes drivers centrally.
Secure print: A feature that holds a job until the user authenticates at the printer to release it.
Cloud printing: Printing through an online service that relays jobs to a printer from any location or device.
Imaging drum: The photosensitive cylinder in a laser printer that holds the charged image of the page.
Fuser: The laser printer assembly that melts toner into paper with heat and pressure.
Maintenance kit: A set of wear parts, usually a fuser and rollers, replaced at a set page count in a laser printer.
Print head: The inkjet component that sprays ink droplets through tiny nozzles onto the paper.
Direct thermal: Printing that darkens heat-sensitive paper without ink, as in receipt printers.
Impact printer: A printer, such as dot matrix, that strikes a ribbon against paper and can print multipart forms.
Filament: The plastic strand fed through a heated extruder in the most common type of 3-D printer.

Domain 4: Virtualization and cloud computing (11%)

Exam tips

Match the goal to the purpose: suspicious file means sandbox, trying changes safely means test/development, one app without installing means application virtualization, and an old program on an outdated operating system means a legacy VM kept isolated.
Type 1 runs on the hardware (bare metal) and is for servers and data centers; Type 2 runs on top of an operating system and is for desktops and testing. Hyper-V is Type 1 even when enabled from Windows.
NAT shares the host's address (outbound works, inbound is hard); bridged gives the VM its own address on the LAN (use for servers); internal isolates VMs from everything else (use for labs). Leave RAM for the host.
Snapshots are for quick rollback, backups are for recovery; they are not interchangeable. Patch each guest and the hypervisor, and patch templates and powered-off VMs as soon as they start. Disable shared clipboard and folders for untrusted content.
Containers share the host kernel and are lightweight and fast; VMs each run a full operating system with stronger isolation. If the question needs a different operating system from the host or maximum isolation, choose a VM.
VDI is on premises and your organization runs the infrastructure; DaaS is the same idea hosted by a cloud provider. Both need reliable network connections. Non-persistent desktops reset at logoff; persistent desktops keep changes.
Deployment models answer who uses and owns it: public (anyone), private (one organization), hybrid (a mix) and community (a group with shared needs). Do not confuse them with the service models IaaS, PaaS and SaaS.
Remember the layers: IaaS means you manage the operating system and up, PaaS means you manage only your code and data, SaaS means you just use the application. Whatever the model, the customer always owns its data and user access.
Elasticity is about quickly scaling with demand; metered is about paying for what you use; high availability is about surviving failures; multitenancy is about many customers sharing one instance. File sync is convenient but is not a backup.

Key terms

Virtual machine: A software-based computer with its own virtual hardware and operating system running on a physical host.
Host: The physical computer whose hardware is shared among virtual machines.
Guest: An operating system running inside a virtual machine.
Sandbox: An isolated, disposable environment for running untrusted software without risk to the host.
Application virtualization: Running a single application isolated from the operating system, often streamed from a server.
Snapshot: A saved point-in-time state of a VM that you can revert to.
Legacy system: An old operating system or application still in use, often no longer supported with updates.
Hypervisor: Software that creates, runs and isolates virtual machines by sharing physical hardware among them.
Type 1 hypervisor: A bare-metal hypervisor installed directly on hardware, used in data centers and servers.
Type 2 hypervisor: A hosted hypervisor that runs as an application on top of a normal operating system.
Bare metal: Running directly on the physical hardware without a general-purpose operating system underneath.
KVM: Kernel-based Virtual Machine, a Type 1 hypervisor built into the Linux kernel.
VT-x / AMD-V: Intel and AMD hardware virtualization features that must be enabled in firmware for hypervisors.
vCPU: A virtual processor assigned to a VM, backed by the host's physical cores and threads.
SLAT: Second level address translation, a CPU feature (Intel EPT, AMD RVI) that speeds memory handling for VMs.
Dynamically expanding disk: A virtual disk that grows as data is written instead of reserving all its space up front.
NAT networking: A VM network mode where the VM shares the host's IP address to reach outside networks.
Bridged networking: A VM network mode that connects the VM directly to the physical network with its own IP address.
Internal networking: A VM network mode that lets VMs communicate only with each other, isolated from outside networks.
Isolation: The separation the hypervisor maintains between VMs and between VMs and the host.
VM escape: An attack in which code in a guest breaks out through a hypervisor flaw to reach the host or other VMs.
Guest patching: Applying operating system and application updates inside each VM, as on a physical computer.
VM sprawl: An uncontrolled growth of VMs that are poorly tracked, managed or patched.
Template: A master VM image used to create new VMs, which must itself be kept up to date.
Container: An isolated package of an application and its dependencies that shares the host operating system's kernel.
Kernel: The core of an operating system that manages hardware, memory and processes.
Container image: A read-only template containing an application and everything it needs, used to start containers.
Container engine: Software such as Docker or containerd that builds, runs and isolates containers.
Microservices: An application design that splits software into small, independently deployable services.
Orchestration: Automated management of many containers across hosts, as done by tools such as Kubernetes.
VDI: Virtual desktop infrastructure, which hosts user desktops as VMs in a data center and delivers them over the network.
DaaS: Desktop as a service, virtual desktops hosted and managed by a cloud provider for a subscription fee.
Connection broker: The VDI component that authenticates users and connects them to the right virtual desktop.
Persistent desktop: A virtual desktop assigned to one user that keeps their changes between sessions.
Non-persistent desktop: A virtual desktop rebuilt from a master image at each login, with changes discarded at logoff.
Thin client: A low-powered device designed mainly to connect to remote desktops and applications.
Public cloud: Cloud infrastructure owned by a provider and shared by many unrelated customers over the internet.
Private cloud: Cloud infrastructure used exclusively by one organization, on premises or hosted on dedicated hardware.
Hybrid cloud: A combination of deployment models, such as private and public, connected to work together.
Community cloud: Cloud infrastructure shared by several organizations with common requirements or concerns.
Cloud bursting: Using public cloud capacity when on-premises or private resources reach their limit.
Deployment model: A description of who owns, uses and hosts a cloud environment.
IaaS: Infrastructure as a service, providing virtual machines, storage and networking while the customer manages the operating system and above.
PaaS: Platform as a service, providing a managed runtime and operating system so customers deploy only code and data.
SaaS: Software as a service, providing a complete application managed entirely by the provider.
Shared responsibility model: The division of security and management duties between cloud provider and customer, which varies by service model.
Lift and shift: Moving existing servers to cloud VMs with little or no redesign, typically using IaaS.
Middleware: Software such as web servers and database engines that sits between the operating system and applications.
Metered utilization: Billing based on measured use of resources such as compute time, storage and data transfer.
Rapid elasticity: The ability to scale resources out or in quickly, often automatically, to match demand.
High availability: Designing services with redundancy and failover so they keep running despite failures.
Multitenancy: One instance of infrastructure or software serving many customers while keeping their data separate.
Dedicated resources: Physical cloud hardware reserved for a single customer rather than shared.
File synchronization: Keeping copies of files consistent across devices and cloud storage automatically.
SLA: Service level agreement, a contract that defines expected service levels such as uptime.

Domain 5: Hardware and network troubleshooting (28%)

Exam tips

Remember the order: identify, theorize, test, plan and implement, verify, document. Back up before making changes. If a theory fails, form a new one or escalate. Documentation is always the last step.
Clock resets mean the CMOS battery. Shutdowns under load mean overheating or a weak PSU. Beeps mean POST errors, so look up the vendor's codes. Burning smell means unplug immediately. Swollen capacitors mean replace the board or PSU, never repair it.
Any sign of drive failure means back up first. Clicking means HDD mechanical failure. A S.M.A.R.T. warning predicts failure. Degraded RAID still runs but has no protection, so replace the drive quickly. RAID is not a backup.
Dim image seen with a flashlight means backlight failure. Blurry text means non-native resolution. A ghost image means burn-in. Projector overheating means filters and ventilation. For no image, check power, input source and cable before replacing hardware.
A swollen battery means stop using and charging immediately and have it replaced. Check software before hardware: app battery usage, airplane mode and settings. For slow charging, try a known-good cable and charger first. Never charge a wet device.
Smudging or toner rubbing off means the fuser or paper type setting. Garbled output means the driver. Repeating marks mean the drum or a roller. A stuck queue means restart the Print Spooler. Multiple sheets feeding means a worn separation pad.
169.254.x.x means DHCP was not reached. Duplicate address warnings mean an IP conflict; keep statics outside the DHCP pool. Jitter hurts voice and video. For wireless trouble, think range, channel, band and interference. Port flapping points to cables or NICs.
Match the tool to the question: RAM means Windows Memory Diagnostic, drive health means CrystalDiskInfo, logs mean Event Viewer, drivers mean Device Manager, IP settings mean ipconfig, reachability means ping, path means tracert, names mean nslookup, cable wiring means cable tester, voltage means multimeter.

Key terms

Troubleshooting methodology: CompTIA's six-step structured process for diagnosing and resolving problems.
Theory of probable cause: A reasoned guess about what is causing a problem, tested before acting on it.
Question the obvious: Checking simple causes such as power and cables before complex ones.
Escalation: Passing a problem to a more experienced technician or specialist team when it cannot be resolved at the current level.
Preventive measures: Actions taken after a fix to stop the problem from happening again.
Documentation: Recording symptoms, cause, actions and outcome so knowledge is kept and reused.
POST: Power-on self-test, the firmware's check of essential hardware at startup.
Beep code: A pattern of beeps from the firmware that identifies a hardware problem during POST.
BSOD: Blue screen of death, a Windows stop error that halts the system and shows a stop code.
Swollen capacitor: A bulging or leaking capacitor that indicates a failing motherboard or power supply.
CMOS battery: A coin cell battery that keeps the firmware clock and settings when the PC is unplugged.
Thermal shutdown: An automatic power-off triggered when a component exceeds a safe temperature.
POST card: An expansion card that displays POST diagnostic codes on boards without built-in diagnostics.
S.M.A.R.T.: Self-Monitoring, Analysis and Reporting Technology, which tracks drive health indicators and predicts failure.
Click of death: Repeated clicking from an HDD whose heads cannot read the platters, signaling imminent failure.
Degraded RAID: A redundant array that has lost a drive and still runs but without its fault tolerance.
Rebuild: The process of restoring a RAID array's redundancy onto a replacement drive.
Boot order: The firmware setting that determines which device the system tries to start from first.
TRIM: A command that tells an SSD which blocks are no longer in use so it can manage them efficiently.
Native resolution: The number of physical pixels in a display panel, which gives the sharpest image.
Backlight: The light source behind an LCD panel that makes the image visible.
Dead pixel: A pixel that never lights, appearing as a permanent black dot.
Stuck pixel: A pixel that remains one color regardless of the image displayed.
Burn-in: A lasting ghost of a static image on a display, mainly OLED and plasma.
Keystone correction: A projector adjustment that corrects a trapezoid-shaped image caused by projecting at an angle.
Input source: The display setting that selects which connector, such as HDMI or DisplayPort, supplies the image.
Charge cycle: One full discharge and recharge of a battery's capacity, which gradually reduces battery health.
Swollen battery: A lithium-ion battery that has expanded due to gas buildup, creating a fire and safety hazard.
Cursor drift: A pointer that moves on the screen without user input, often from touchpad issues.
Liquid contact indicator: A small sticker inside a device that changes color when exposed to liquid.
Airplane mode: A setting that turns off the device's wireless radios.
Battery saver: A mode that reduces background activity and performance to extend battery life.
Fuser: The laser printer component that melts toner into paper with heat and pressure.
Ghosting: Faint repeated images on a page, usually from incomplete drum cleaning or a worn drum.
Print Spooler: The Windows service that queues print jobs and sends them to the printer.
Pickup roller: The roller that grabs paper from the tray and feeds it into the printer.
Separation pad: A part that ensures only one sheet feeds at a time, preventing multiple-sheet jams.
Toner density: A setting that controls how much toner is applied, affecting how dark prints appear.
APIPA: Automatic Private IP Addressing, a self-assigned 169.254.x.x address used when DHCP cannot be reached.
IP conflict: Two devices on the same network using the same IP address, disrupting connectivity.
Latency: The time it takes data to travel to a destination and back, measured in milliseconds.
Jitter: Variation in latency that disrupts real-time services such as voice and video calls.
SSID: Service set identifier, the name of a wireless network.
Port flapping: A switch port rapidly and repeatedly changing between up and down states.
Interference: Radio noise from other devices or networks that degrades wireless performance.
Windows Memory Diagnostic: A built-in Windows tool that tests RAM for errors during a restart.
CrystalDiskInfo: A third-party utility that displays a drive's S.M.A.R.T. health data.
Event Viewer: A Windows tool that displays system, application and security logs.
Device Manager: A Windows tool that lists hardware devices and manages their drivers.
tracert: A command that shows each router hop on the path to a destination.
nslookup: A command that queries DNS to check how names resolve to IP addresses.
Cable tester: A device that checks network cables for continuity, shorts and correct wiring.
Multimeter: An instrument that measures voltage, resistance and continuity.

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