CompTIA A+ Core 1 (220-1101) Cheat Sheet 2026 — Ports, Connectors, Hardware & Troubleshooting

Domain 1: Mobile Devices (15%)

• Laptop Components: LCD/OLED display, inverter (older CCFL), Wi-Fi antenna wires (route around screen), webcam, microphone, keyboard, trackpad, battery (Li-Ion), DC jack, RAM (SO-DIMM), SSD/HDD (2.5").
• Mobile Display Types: IPS (best color, no viewing angle issue), OLED (deep blacks, each pixel self-lights), TN (cheap, poor viewing angle), AMOLED (OLED variant, mobile).
• Mobile Connectivity: Wi-Fi (802.11 a/b/g/n/ac/ax), Bluetooth (pairing, discoverable mode), NFC (tap to share, 4 cm range), hotspot/tethering, USB-C charging.
• iOS vs Android: iOS = closed ecosystem, Apple App Store, iTunes/Finder for backup. Android = open, Google Play, APK sideloading, MDM enrollment.
• Wearable Devices: Smartwatches, fitness trackers. Sync via Bluetooth to phone. ECG, SpO2, fall detection sensors.
• Mobile Sync Methods: Sync to cloud (iCloud, Google), sync to desktop (iTunes/Finder, Android File Transfer). Synchronize contacts, email, photos, calendar.

Domain 2: Networking Technology (20%)

• OSI Model (top to bottom): Application, Presentation, Session, Transport, Network, Data Link, Physical. All People Seem To Need Data Processing.
• TCP vs UDP: TCP = reliable, ordered, three-way handshake. UDP = fast, no guarantee, no order (streaming, gaming, DNS, VoIP).
• Common Ports: See port table below. Memorize all of them.
• IPv4 Classes: Class A (1-126), Class B (128-191), Class C (192-223), Class D (multicast 224-239), Class E (experimental 240-255).
• Private IP Ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16 (APIPA).
• Subnet Mask: /24 = 255.255.255.0 (254 usable hosts). /16 = 255.255.0.0 (65,534 hosts). /30 = 255.255.255.252 (2 usable hosts).
• Cable Types: Cat 5e (1 Gbps, 100 m), Cat 6 (10 Gbps up to 55 m), Cat 6a (10 Gbps, 100 m), Cat 7/8 (higher shielding).
• Connectors: RJ-45 (Ethernet), RJ-11 (phone), LC/SC/ST (fiber), BNC (coaxial), F-type (coax TV/cable).
• Wireless Standards: 802.11ac (Wi-Fi 5, 5 GHz, up to 3.5 Gbps), 802.11ax (Wi-Fi 6, 2.4+5 GHz, up to 9.6 Gbps), 802.11be (Wi-Fi 7, tri-band).
• Network Devices: Router (Layer 3, routes between networks), Switch (Layer 2, MAC table), Hub (Layer 1, broadcasts), Access Point (wireless bridge), Firewall (filters traffic).
• DHCP: Assigns IP, subnet mask, gateway, DNS automatically. DORA process: Discover, Offer, Request, Acknowledge.
• DNS: Domain Name System. Resolves domain names to IP addresses. A record (IPv4), AAAA (IPv6), CNAME (alias), MX (mail), PTR (reverse).

Domain 3: Hardware (25%)

• Motherboard Form Factors: ATX (standard), Micro-ATX (smaller), Mini-ITX (smallest common), ITX.
• CPU Sockets: Intel: LGA 1700 (current), LGA 1200. AMD: AM5 (current), AM4, sTR5 (Threadripper).
• RAM Types: DDR4 (3200 MHz common), DDR5 (4800+ MHz, newer). SO-DIMM for laptops. ECC for servers. Dual/quad channel for performance.
• Storage: HDD (spinning platters, SATA, slowest), SATA SSD (2.5", 6 Gbps), NVMe SSD (M.2 slot, PCIe, fastest, up to 7000 MB/s). eMMC (budget laptops, embedded).
• GPU: Integrated (Intel UHD, AMD Radeon) vs Dedicated (NVIDIA RTX, AMD Radeon RX). PCIe x16 slot. VRAM (GDDR6/GDDR6X).
• Power Supply (PSU): ATX 24-pin motherboard, 4/8-pin CPU, 6/8-pin PCIe. Wattage must exceed total component draw. 80 PLUS ratings (Bronze, Gold, Platinum, Titanium).
• Cooling: Air (heatsink + fan), Liquid (AIO closed-loop, custom loop), Thermal paste (between CPU and heatsink). Case fans: intake (front), exhaust (rear/top).
• BIOS/UEFI: BIOS = legacy, 16-bit. UEFI = modern, GUI, secure boot, GPT disks (drives > 2 TB), fast boot.
• Expansion Cards: PCIe x1 (small), x4, x8, x16 (GPU). Legacy: PCI, AGP.
• Printers: Inkjet (liquid ink, photo quality), Laser (toner, fast, fuser unit), Thermal (receipts, heat-sensitive paper), 3D (additive manufacturing, PLA/ABS filament).

Domain 4: Virtualization & Cloud Computing (10%)

• Virtualization: Hypervisor creates VMs. Type 1 (bare-metal: VMware ESXi, Hyper-V, Proxmox). Type 2 (hosted: VirtualBox, VMware Workstation).
• VM Resources: vCPU, vRAM, virtual disk (VHD/VHDX), virtual NIC, virtual switch.
• Cloud Models: SaaS (software: Gmail, Office 365), PaaS (platform: Heroku, App Engine), IaaS (infrastructure: EC2, Azure VM).
• Cloud Deployment: Public (shared infrastructure), Private (dedicated), Hybrid (mix of both), Community (shared by orgs with common goals).
• Client-Side Virtualization: VMs for testing, legacy apps, sandbox. Resource-heavy — needs enough host RAM and CPU.

Domain 5: Hardware & Network Troubleshooting (30%)

This is the largest domain. You must know the structured troubleshooting methodology and common symptoms-to-cause mappings.

• Troubleshooting Methodology: 1. Identify the problem → 2. Establish a theory → 3. Test the theory → 4. Establish a plan of action → 5. Verify full functionality → 6. Document findings.
• No Power: Check outlet, power cable, PSU switch, PSU voltage switch (115V/230V), motherboard LED, front panel connectors.
• No Display: Check monitor power, cable connection, input source, GPU seated, RAM seated, beep codes, BIOS reset (CMOS battery).
• Overheating: Check fans spinning, thermal paste, dust buildup, case airflow, heatsink mounting, temperature in BIOS.
• POST Beep Codes: 1 short = normal. Continuous = RAM error. 1 long 2 short = video error. 1 long 3 short = memory issue (AMI BIOS).
• Slow Performance: Check Task Manager for CPU/RAM/Disk usage. Malware scan. Check startup programs. Defragment HDD (not SSD). Check free disk space.
• No Network: Check cable, link lights, IP config (ipconfig), ping loopback (127.0.0.1), ping gateway, ping 8.8.8.8, nslookup, check DHCP.
• Intermittent Network: Check cable for damage, EMI sources, switch port, wireless interference, driver updates.
• Printer Issues: Paper jam, toner low, fuser failure (paper not fusing), streaks (drum or toner), garbled output (driver issue), network printer offline (check IP/port).

Common Port Numbers

Connector Quick Reference

Frequently Asked Questions