CompTIA A+ Core 1 (220-1101) — One-Hour Cram Sheet

High-yield facts across all five domains · built for a final review pass

90 questions max 90 minutes Multiple-choice + performance-based Scaled 100–900, pass 675 Mobile 13% · Net 23% · HW 25% · Cloud 11% · Troubleshoot 28%

Strategy: Troubleshooting (28%) + Networking (23%) + Hardware (25%) = 76% of the exam. Spend most of your hour there. Read each question fully — watch for words like FIRST, BEST, MOST likely, and "choose two."

1. Troubleshooting Methodology & Common Scenarios ~28%

The 6-Step CompTIA Process (memorize the order)

Identify the problem — gather info, question the user, identify changes, back up before making changes.
Establish a theory of probable cause (question the obvious; consider "easiest fixes first").
Test the theory to determine cause. If confirmed → next step. If not → new theory or escalate.
Establish a plan of action to resolve the problem and implement the solution.
Verify full system functionality and, if applicable, implement preventive measures.
Document findings, actions, and outcomes.

Mnemonic: "Identify, Theorize, Test, Plan, Verify, Document."

Hardware symptom → likely cause

Symptom	Most likely cause / first action
No display, fans spin, memory beep code	RAM — reseat / test modules
Continuous reboots / shutdown under load, high temps	Overheating (fan, dust, dried thermal paste) or failing PSU
Burning smell or smoke	Power off & unplug immediately; suspect PSU. Never open a PSU.
Clicking / grinding HDD, files vanishing	Failing drive — back up data now, then replace (ideally with SSD)
Frequent random BSODs after RAM upgrade	Faulty / unseated RAM — reseat, run MemTest
Bulging / leaking capacitors	Failing motherboard — replace board
Date/time & BIOS settings reset when unplugged	Dead CMOS battery (CR2032)
Black laptop screen but external monitor works	Internal panel, display cable, or backlight
Distorted / artifact graphics, worse when hot	GPU overheating / failing card / bad driver
No power at all (no fans/lights), outlet good	PSU switch/voltage selector, then test/replace PSU

Printer symptom → cause

Symptom (printer type)	Cause / fix
Faded print, whole page (laser)	Low toner
Ghost / repeated faint image (laser)	Worn imaging drum or failing fuser
Toner smears / rubs off (laser)	Fuser not heating
Vertical lines / missing lines (laser)	Scratched/dirty drum
Horizontal white gaps, missing lines (inkjet)	Clogged nozzles — run head cleaning / nozzle check
Frequent paper jams (any)	Worn pickup rollers, wrong paper, debris in path

Network symptom → cause

Symptom	Cause / next step
Can ping by IP, not by name	DNS problem — check DNS settings (nslookup)
Address is `169.254.x.x` (APIPA)	No DHCP lease — check cable, switch port, DHCP server
No connectivity, NIC link light off	Layer 1 — check cable & switch port first
Slow / intermittent on a gig link	Duplex / speed mismatch, or interference (wireless)
Weak Wi-Fi far from AP	Coverage — reposition/add AP, repeater/mesh, change channel

2. Networking ~23%

Common Ports (very high yield) — TCP / UDP / both

Port	Service
20 / 21 T	FTP (data / control)
22 T	SSH, SFTP, SCP
23 T	Telnet (insecure)
25 T	SMTP (send mail)
53 T/U	DNS
67 / 68 U	DHCP (server / client)
69 U	TFTP
80 T	HTTP
110 T	POP3 (download mail)

Port	Service
137-139 T/U	NetBIOS / NetBT
143 T	IMAP (sync mail)
161 / 162 U	SNMP
389 T/U	LDAP
443 T	HTTPS (HTTP+TLS)
445 T	SMB / CIFS (file share)
3389 T	RDP (remote desktop)
993 / 995 T	IMAPS / POP3S (secure)
636 T	LDAPS (secure LDAP)

SSH (22) replaces Telnet (23) — both remote CLI, but SSH is encrypted. Secure mail: SMTP-S 465/587, IMAPS 993, POP3S 995.

Copper & Fiber Cabling

Cable	Speed / notes
Cat 5	100 Mbps (Fast Ethernet)
Cat 5e	1 Gbps, reduced crosstalk
Cat 6	1 Gbps @100m; 10 Gbps only to ~55m
Cat 6a	10 Gbps @ full 100m
Cat 7 / 8	Shielded; 10 Gbps (Cat8 up to 40 Gbps, short)
Coax RG-6 / RG-59	Cable internet/TV (RG-6 thicker, longer) / CCTV (RG-59)
Multimode fiber	Short distance, LED, larger core (orange/aqua)
Single-mode fiber	Long distance (km), laser, tiny core (yellow)

Max UTP copper run: 100m (328 ft).
Plenum cable required in HVAC air spaces (low-smoke jacket).
Connectors: RJ45 = Ethernet (8P8C); RJ11 = phone; F-type/BNC = coax; LC/SC/ST = fiber.
Wiring: T568A/B; straight-through = different devices, crossover = like devices (auto-MDIX now common).

Wireless Standards (802.11)

Std	Wi-Fi name	Band	Max (approx)
a	—	5 GHz	54 Mbps
b	—	2.4 GHz	11 Mbps
g	—	2.4 GHz	54 Mbps
n	Wi-Fi 4	2.4 & 5 GHz	600 Mbps (MIMO)
ac	Wi-Fi 5	5 GHz only	~1.3+ Gbps (MU-MIMO)
ax	Wi-Fi 6 / 6E	2.4 & 5 GHz (6E adds 6 GHz)	~9.6 Gbps

2.4 GHz: better range/penetration, more interference; non-overlapping channels 1, 6, 11.
5 GHz: faster, shorter range, more channels.
Bluetooth 2.4 GHz (~10m class 2). NFC ~4cm, contactless pay. RFID tags.

IP Addressing & DNS

IPv4 = 32-bit; IPv6 = 128-bit (hex, colons).
Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
APIPA 169.254.0.0/16 = no DHCP reached. Loopback 127.0.0.1.
/24 = 255.255.255.0; /16 = 255.255.0.0.
NAT maps many private IPs to one public IP.
DHCP gives: IP, subnet mask, default gateway, DNS.
DNS records: A=IPv4, AAAA=IPv6, CNAME=alias, MX=mail, TXT=SPF/DKIM/verify, PTR=reverse.
VLAN segments a switch logically; VPN tunnels encrypted over internet.

Network Devices & Concepts

Router = Layer 3, routes between networks.
Switch = Layer 2, forwards by MAC address.
Hub = Layer 1, repeats to all ports (dumb).
Access point bridges wireless to wired.
Firewall filters traffic by rules/ports.
PoE = power + data over one Ethernet cable (APs, cameras).
ONT = fiber to Ethernet; modem = ISP signal to digital.
Cloud/SDN, NAS (file storage), legacy: 56k modem, dial-up.

3. Hardware ~25%

Memory (RAM)

Type	Voltage	Desktop / Laptop pins
DDR3	1.5 V	240-pin DIMM / 204-pin SODIMM
DDR4	1.2 V	288-pin DIMM / 260-pin SODIMM
DDR5	1.1 V	288-pin DIMM / 262-pin SODIMM

Generations are NOT interchangeable (different notch, voltage); slot is keyed.
SODIMM = laptop / small form factor.
ECC = error-correcting (servers); detects+corrects single-bit errors.
Dual/quad channel = matched sticks in matching (color-coded) slots for more bandwidth.
XMP/EXPO = enable rated overclock speeds in BIOS.

Storage & RAID

HDD: platters + heads, moving parts; 5400/7200 RPM; cheap per TB.
SSD: no moving parts, faster, quieter.
SATA III = 6 Gb/s (~600 MB/s). SATA I=1.5, II=3.
M.2 form factor; NVMe runs over PCIe — far faster than SATA.
M.2 keys: B, M, B+M (storage); A/E (Wi-Fi).
eMMC (cheap soldered), eSATA (external).

RAID	What / min disks
0	Stripe, speed, no redundancy (min 2)
1	Mirror, redundancy (min 2)
5	Stripe + parity, 1-disk fault (min 3)
6	Stripe + double parity, 2-disk fault (min 4)
10	Mirror + stripe (min 4)

Expansion, Power, CPU & Cooling

PCIe x16 = graphics card; also x1/x4/x8. Backward compatible.
Power: 24-pin main board, 4/8-pin EPS = CPU, 6/8-pin PCIe = GPU, SATA & Molex for drives.
PSU rails: +3.3V, +5V, +12V; pick adequate wattage; redundant PSUs in servers.
CPU sockets: LGA = pins on board (Intel); PGA = pins on CPU (older AMD); ZIF lever.
Cooling: heatsink + fan, or liquid (AIO). Thermal paste fills gaps for heat transfer.
Motherboard sizes (large→small): E-ATX > ATX > microATX > Mini-ITX.
CMOS battery = CR2032 (keeps clock/BIOS). POST runs at boot; beep codes signal errors.
UEFI/BIOS: Secure Boot, TPM (encryption keys), boot order.

Display & Peripheral Interfaces

Interface	Key facts
VGA	Analog video only (blue, 15-pin)
DVI	DVI-A analog, DVI-D digital, DVI-I both; video only
HDMI	Digital video + audio; common on TVs
DisplayPort	Digital A/V; MST daisy-chains monitors
Thunderbolt 3/4	USB-C connector, up to 40 Gb/s, A/V + data + power

USB	Speed
USB 2.0 (Hi-Speed)	480 Mb/s
USB 3.0 / 3.1 Gen1 / 3.2 Gen1 (SuperSpeed, blue)	5 Gb/s
USB 3.1 Gen2 / 3.2 Gen2	10 Gb/s
USB 3.2 Gen 2x2	20 Gb/s
USB4	up to 40 Gb/s (USB-C)

USB-C = reversible connector (not a speed). USB-A max cable ~5m (2.0) / ~3m (3.x).

Printers

Laser: toner, drum, laser, heated fuser. Imaging order: Processing → Charging → Exposing → Developing → Transferring → Fusing → Cleaning.
Inkjet: liquid ink, printheads; clean nozzles for gaps.
Thermal: heats special paper (receipts).
Impact (dot-matrix): pins strike ribbon — only type for multi-part carbon forms.
3D: FDM (filament), resin (SLA).

4. Mobile Devices ~13%

USB-C = modern Android/laptops (reversible, data+power); Lightning = older Apple; microUSB legacy.
Digitizer = touch layer (image fine but no touch → replace digitizer).
Inverter = powers CCFL backlight (dim/faint image on old laptops).
Wi-Fi antenna wires usually run through the display bezel.
Laptop RAM = SODIMM; storage often M.2; Wi-Fi card = M.2 A/E.
Hotspot/tethering shares cellular (Wi-Fi/USB/Bluetooth).
NFC = tap-to-pay; Bluetooth pairing; GPS = location.
Cellular: LTE/5G; eSIM vs physical SIM; PRL/baseband updates.
Sync to cloud keeps mail/contacts/calendar across devices.
Security: screen lock/biometrics, remote wipe, full-device encryption, MDM, find-my-device.
Swollen battery: stop using, replace, recycle safely — never puncture/freeze.
Display toggle = Fn + monitor key; airplane mode disables radios.

5. Virtualization & Cloud Computing ~11%

Service Models (who manages what)

Model	You manage	Example
IaaS	OS & up (VMs, storage, net rented)	Cloud VMs / servers
PaaS	Just your app/code	Managed dev platform
SaaS	Nothing — just use it	Webmail, online office

Deployment, Characteristics & Hypervisors

Deployment: Public, Private, Hybrid (mix/burst), Community.
5 traits: on-demand self-service, broad network access, resource pooling (multitenancy), rapid elasticity, measured service (pay-as-you-go).
Type 1 hypervisor = bare-metal (no host OS). Type 2 = hosted (runs on an OS).
VMs need host CPU/RAM/disk + VT-x / AMD-V enabled in BIOS.
Sandbox = isolated test environment for untrusted code.
Cloud file sync & cloud backup; high availability & metered billing.

Rapid recall: SSH=22 · RDP=3389 · HTTPS=443 · DNS=53 · DHCP=67/68 · SMB=445 · SMTP=25 · IMAP=143 · POP3=110 · LDAP=389 | Cat6a=10G@100m · SATA III=6Gb/s · TB3=40Gb/s · RAID5 min 3 / RAID10 min 4 · CMOS=CR2032 · PCIe x16=GPU · Wi-Fi6=ax.