Plain-English definitions of the terms that come up most often in CompTIA A+ study, spanning both Core 1 (220-1201) and Core 2 (220-1202). Definitions are simplified for learning; the official objectives are authoritative.
| Term | Definition |
|---|---|
| BIOS / UEFI | Firmware that initialises hardware and starts the boot process; UEFI is the modern replacement for BIOS. |
| POST | Power-On Self-Test: the firmware’s hardware check at startup; failures are often reported as beep codes. |
| CMOS battery | Small motherboard battery that preserves firmware settings and the clock while the PC is unplugged. |
| DIMM / SODIMM | Memory module form factors: full-size DIMMs for desktops, smaller SODIMMs for laptops. |
| DDR | Double Data Rate memory; generations (DDR3/DDR4/DDR5) are keyed differently and do not interchange. |
| HDD | Hard disk drive: mechanical spinning-platter storage; cheap capacity but the slowest internal option. |
| SSD | Solid-state drive: flash storage with no moving parts; far faster and more shock-resistant than an HDD. |
| NVMe / M.2 | NVMe is a flash-storage protocol that runs over PCIe for top speed; M.2 is the compact slot it commonly uses. |
| SATA | The standard interface for connecting internal drives to the motherboard. |
| RAID | Combining drives into one logical volume: RAID 0 stripes, 1 mirrors, 5 adds parity, 10 mirrors and stripes. |
| PSU | Power supply unit: converts wall AC into the regulated DC voltages the components run on. |
| GPU | Graphics processing unit: renders images and video, either as a dedicated card or integrated in the CPU. |
| ESD | Electrostatic discharge: static electricity that can destroy components; prevented with a wrist strap and grounding. |
| RJ45 | The 8-pin connector used for wired Ethernet (RJ11 is the smaller telephone version). |
| TCP | Transmission Control Protocol: connection-oriented transport with acknowledgements and retransmission. |
| UDP | User Datagram Protocol: connectionless, fast transport used where occasional loss is acceptable. |
| IP address | The logical address that identifies a device on a network. |
| Subnet mask | The value that splits an IP address into its network part and its host part. |
| Default gateway | The router address a device uses to reach anything outside its own subnet. |
| DHCP | The service that automatically hands devices an IP address and related settings when they join a network. |
| DNS | The service that resolves human-readable names into IP addresses. |
| NAT | Network Address Translation: lets many private internal addresses share one public address. |
| VPN | Virtual private network: an encrypted tunnel across an untrusted network. |
| SSID | The broadcast name of a wireless network. |
| Access point | A device that bridges wireless clients into a wired network. |
| Hypervisor | Software that runs and manages virtual machines on shared physical hardware. |
| Virtual machine | A complete software computer, with its own operating system, running on a hypervisor. |
| IaaS / PaaS / SaaS | Cloud service models: rented infrastructure, a managed platform, or a finished application. |
| Cloud deployment models | Who the cloud serves: public (shared), private (dedicated), hybrid (a mix), community (a sector). |
| Troubleshooting methodology | CompTIA’s ordered steps: identify, theorise, test, plan and implement, verify, document. |
| NTFS | The standard Windows file system, supporting permissions, encryption and large volumes. |
| Task Manager | The Windows tool showing live processes, performance and startup items. |
| Event Viewer | The Windows tool that stores logs of application crashes, errors and system events. |
| Device Manager | The Windows tool for managing hardware devices and their drivers. |
| Disk Management | The Windows tool for creating, formatting and resizing partitions and volumes. |
| Safe Mode | A Windows startup mode that loads minimal drivers, used to remove faulty updates or malware. |
| Malware | Umbrella term for malicious software: viruses, trojans, ransomware, spyware, rootkits and more. |
| Ransomware | Malware that encrypts a victim’s files and demands payment for their release. |
| Phishing | Fraudulent messages that impersonate trusted senders to steal credentials or data. |
| Social engineering | Manipulating people, rather than technology, to bypass security. |
| MFA | Multi-factor authentication: proving identity with two or more different factors. |
| UAC | User Account Control: the Windows prompt that asks for confirmation before system-level changes. |
| Least privilege | Giving users and accounts only the access they strictly need. |
| BitLocker | Windows full-disk encryption, protecting data if a device is lost or stolen. |
| WPA3 | The current Wi-Fi security standard, replacing WPA2; WEP and WPA are obsolete and insecure. |
| Chain of custody | The documented, unbroken handling of evidence so it remains trustworthy and admissible. |
| AUP | Acceptable use policy: the rules for what users may and may not do on company systems. |
| Change management | The controlled process for changes: request, approval, testing and a rollback plan. |
| PII | Personally identifiable information: data that identifies a person and must be protected. |