Resource Cheatsheets

Code ch. 1 — Morse code as a first code: dots, dashes and timing, why common letters are short, and what a code actually is.

Updated 18 Sept 2026Ch. 1

Code ch. 2 — counting Morse combinations, why two symbols of length n give 2ⁿ codes, and decoding with a binary tree.

Updated 18 Sept 2026Ch. 2

Code ch. 3 — Braille's six-dot cells as a binary code, 64 combinations, and shift/escape codes that change what the next symbol means.

Updated 18 Sept 2026Ch. 3

Code ch. 4 — a circuit from battery, bulb and switch: voltage, current, resistance, Ohm's law, power, series vs parallel, conductors and insulators.

Updated 18 Sept 2026Ch. 4

Code ch. 5 — signalling by wire between houses: circuits need a return path, shared commons and earth grounds, and why long wires dim the signal.

Updated 18 Sept 2026Ch. 5

Code ch. 6 — Boolean algebra (AND, OR, NOT), sets and conditions, and how switches in series and parallel perform logic.

Updated 18 Sept 2026Ch. 6

Code ch. 7 — the telegraph key and sounder, why long lines fail, and the relay: a switch flipped by electricity that regenerates the signal.

Updated 18 Sept 2026Ch. 7

Code ch. 8 — building AND, OR, NOT, NAND and NOR gates from relays, truth tables, gate symbols and De Morgan's laws.

Updated 18 Sept 2026Ch. 8

Code ch. 9 — why we count in tens, Roman numerals vs positional notation, the importance of zero, and how place value works in any base.

Updated 18 Sept 2026Ch. 9

Code ch. 10 — counting in other bases: octal, base 4 and binary, converting between them, and where octal still shows up in Linux permissions.

Updated 18 Sept 2026Ch. 10

Code ch. 11 — the bit as a yes/no answer, 2ⁿ possibilities, how many bits a choice needs, barcodes with check digits, and QR codes.

Updated 18 Sept 2026Ch. 11

Code ch. 12 — the 8-bit byte, nibbles, hexadecimal digits and conversion, hex notation, and where hex appears in everyday IT.

Updated 18 Sept 2026Ch. 12

Code ch. 13 — text as numbers: Baudot and shift codes, 7-bit ASCII and control characters, code pages, Unicode, and UTF-8/16/32.

Updated 18 Sept 2026Ch. 13

Code ch. 14 — binary addition, XOR, the half adder and full adder, chaining them into an 8-bit ripple-carry adder, and overflow.

Updated 18 Sept 2026Ch. 14

Code ch. 15 — from mechanical calculators and relay machines to vacuum tubes, transistors, integrated circuits and the microprocessor.

Updated 18 Sept 2026Ch. 15

Code ch. 16 — subtracting with an adder: nines' complement, ones' and two's complement, signed numbers, and overflow.

Updated 18 Sept 2026Ch. 16

Code ch. 17 — feeding outputs back to inputs: the oscillator (a clock), R-S flip-flops, D latches, edge-triggered flip-flops, dividers and counters.

Updated 18 Sept 2026Ch. 17

Code ch. 18 — a digital clock from counters: binary-coded decimal, dividing a fast oscillator down to 1 Hz, and driving seven-segment displays.

Updated 18 Sept 2026Ch. 18

Code ch. 19 — building RAM from latches: addresses, decoders to write, selectors to read, address lines vs capacity, and why RAM is volatile.

Updated 18 Sept 2026Ch. 19

Code ch. 20 — adder plus memory plus a counter: stepping through memory automatically, then storing instruction codes alongside data.

Updated 18 Sept 2026Ch. 20

Code ch. 21 — the ALU: add/subtract plus AND, OR, XOR selected by a function code, with status flags for carry, zero and sign.

Updated 18 Sept 2026Ch. 21

Code ch. 22 — registers as fast on-chip storage, the data/address/control busses that move bytes around, three-state buffers, and the fetch-execute cycle.

Updated 18 Sept 2026Ch. 22

Code ch. 23 — the control unit: turning opcodes into the timed signals that steer registers, ALU and memory, instruction sets and microcode.

Updated 18 Sept 2026Ch. 23

Code ch. 24 — changing the program counter: unconditional and conditional jumps, loops, the stack, and CALL/RETURN for subroutines.

Updated 18 Sept 2026Ch. 24

Code ch. 25 — getting data in and out: I/O ports vs memory-mapped I/O, polling vs interrupts, DMA, and device controllers.

Updated 18 Sept 2026Ch. 25

Code ch. 26 — why raw hardware needs an OS: the kernel, system calls, processes and multitasking, memory management, file systems and drivers.

Updated 18 Sept 2026Ch. 26

Code ch. 27 — from machine code to high-level languages: assemblers, compilers vs interpreters, high-level constructs, libraries and APIs.

Updated 18 Sept 2026Ch. 27

Code ch. 28 — graphics, sound, networks, the internet and the web tying it all together, plus a look at where computing goes next.

Updated 18 Sept 2026Ch. 28

TCM Practical Help Desk section 1 — what the course covers, how lessons are formatted, lab requirements, and how to ask for help well.

Updated 18 Sept 2026§1

TCM Practical Help Desk section 2 — what IT does, the IT org chart and roles, help desk tiers and responsibilities, and reading job postings.

Updated 18 Sept 2026§2

TCM Practical Help Desk section 3 — binary, bits and bytes, character encoding, logic gates and how a CPU computes, compilers and abstraction.

Updated 18 Sept 2026§3

TCM Practical Help Desk section 4 — ESD, CPU, RAM, drives, PSU, GPU, motherboard, ports and peripherals, POST and the BIOS, plus commands to inspect hardware.

Updated 18 Sept 2026§4

TCM Practical Help Desk section 5 — opening laptops safely, batteries, SODIMM RAM, laptop drives, the CMOS battery and other internal parts.

Updated 18 Sept 2026§5

TCM Practical Help Desk section 6 — what an OS does, kernel vs userland, file systems and partition styles, and file types, with commands to check each.

Updated 18 Sept 2026§6

Pre Security module 1 — what cyber security is, offensive vs defensive work, core terms, career paths, and staying on the right side of the law.

Updated 18 Sept 2026Module 1

Pre Security module 2 — what's inside a computer, how components connect, the boot process, and the many types of computer you'll need to secure.

Updated 18 Sept 2026Module 2

Pre Security module 3 — what an OS does, Windows basics (interface, system tools, apps, files, security settings) and Linux basics, with the commands for each.

Updated 18 Sept 2026Module 3

Pre Security module 4 — data representation, Python and JavaScript fundamentals side by side, and databases with SQL.

Updated 18 Sept 2026Module 4

Pre Security module 5, What is Networking? — networks and the internet, private vs public, IP vs MAC addresses, MAC spoofing, IPv4 vs IPv6, and ping.

Updated 22 Sept 2026What is Networking?

Pre Security module 5, Intro to LAN — star, bus and ring topologies, switches vs hubs, routers, subnetting and address roles, ARP request/reply, and DHCP DORA.

Updated 22 Sept 2026Intro to LAN

Pre Security module 5, OSI Model — the seven layers and what each does, addresses and devices per layer, TCP vs UDP, and encapsulation.

Updated 22 Sept 2026OSI Model

Pre Security module 5, Packets & Frames — packet vs frame, IP and TCP headers, the three-way handshake and close, UDP, and port numbers and ranges.

Updated 22 Sept 2026Packets and Frames

Pre Security module 5, Extending Your Network — port forwarding, stateful vs stateless firewalls, VPNs and VPN protocols, routers, layer 2 vs layer 3 switches, and VLANs.

Updated 22 Sept 2026Extending Your Network

TryHackMe module 6 — TLD/SLD/subdomain structure, A/AAAA/CNAME/MX/TXT records, and the DNS resolution journey with TTL caching.

Updated 27 Sept 2026DNS in Detail

TryHackMe module 7 — HTTP/HTTPS, URL structure, requests/responses, HTTP methods, status codes, headers, and cookies.

Updated 27 Sept 2026HTTP in Detail

TryHackMe module 8 — front end vs back end, HTML/CSS/JS, page source, sensitive data exposure, and HTML injection.

Updated 27 Sept 2026How Websites Work

TryHackMe module 9 — load balancers, CDNs, databases, WAFs, web server software, virtual hosts, and static vs dynamic content.

Updated 27 Sept 2026Putting It All Together

Professor Messer A+ 220-1201 section 1 — laptop hardware, connecting and accessorising mobile devices, cellular and wireless connectivity, and MDM.

Updated 18 Sept 2026Mobile Devices

Professor Messer A+ 220-1201 lesson 1.1 — laptop batteries, keyboards, SO-DIMM memory, 2.5-inch vs M.2 storage, HDD-to-SSD cloning, wireless cards and antennas, biometrics, NFC and cameras.

Updated 20 Sept 2026Laptop Hardware

Professor Messer A+ 220-1201 lesson on connecting mobile devices — mini/micro-USB, Type-A, USB-C, Lightning, NFC, Bluetooth PAN, hotspot vs tethering.

Updated 20 Sept 2026Mobile Device Connections

Professor Messer A+ 220-1201 lesson on mobile accessories — stylus, headsets and TRRS, speakers, webcams, docking station vs port replicator, trackpads and drawing pads.

Updated 20 Sept 2026Mobile Device Accessories

Professor Messer A+ 220-1201 lesson on MDM — BYOD, COPE, CYOD, partitioning, policies and restrictions, the MDM console and IMEI, over-the-air sync and business app accounts.

Updated 20 Sept 2026Mobile Device Management

Professor Messer A+ 220-1201 section 2 — IP, TCP/UDP and ports, wireless, network services, DNS/DHCP/VLAN/VPN, devices, IP addressing, connection types and tools.

Updated 22 Sept 2026Networking

Professor Messer A+ 220-1201 networking primer — encapsulation, TCP vs UDP, multiplexing, IP addresses, well-known vs ephemeral ports, reading a protocol decode.

Updated 20 Sept 2026Introduction to IP

Professor Messer A+ 220-1201 objective 2.1 — FTP, SSH, Telnet, SMTP, DNS, DHCP, HTTP/HTTPS, POP3, IMAP, SMB/CIFS, NetBIOS, LDAP and RDP port numbers.

Updated 20 Sept 2026Common Ports

Professor Messer A+ 220-1201 objective 2.2 — 802.11/Wi-Fi naming, frequency bands, channels and bandwidth, Bluetooth and ISM, RFID passive/active tags, and NFC.

Updated 20 Sept 2026Wireless Networking Protocols

Professor Messer A+ 220-1201 objective 2.3 — DNS, DHCP, file/print sharing, email, syslog/SIEM, web, AAA, database, NTP, spam gateway, UTM, load balancer, proxy, SCADA/ICS, legacy, embedded and IoT.

Updated 20 Sept 2026Network Services

Professor Messer A+ 220-1201 objective 2.4 — DNS hierarchy and root servers, dig/nslookup, resource records, A/AAAA, CNAME, MX, TXT, DKIM, SPF and DMARC.

Updated 20 Sept 2026Domain Name System (DNS)

Professor Messer A+ 220-1201 objective 2.4 — why DHCP exists, the DORA process with exact packet fields, scopes, pools and exclusions, and DHCP reservations.

Updated 20 Sept 2026Dynamic Host Configuration Protocol (DHCP)

Professor Messer A+ 220-1201 objective 2.4 — broadcast domains, LANs, VLANs and inter-VLAN routing, VPN concentrators, client-to-site vs site-to-site VPN.

Updated 20 Sept 2026VLANs and VPNs

Professor Messer A+ 220-1201 objective 2.5 — routers, managed vs unmanaged switches, access points, patch panels, firewalls, PoE standards, cable/DSL/ONT and NICs.

Updated 22 Sept 2026Network Devices

Professor Messer A+ 220-1201 objective 2.6 — IPv4 octets and binary, RFC 1918 private ranges and NAT, IPv6 hex notation, shortening rules, address types and /64.

Updated 22 Sept 2026IPv4 and IPv6

Professor Messer A+ 220-1201 objective 2.6 — IP address, subnet mask and gateway; static vs dynamic vs DHCP reservation; APIPA range and its ARP check.

Updated 22 Sept 2026Assigning IP Addresses

Professor Messer A+ 220-1201 objective 2.7 — satellite (GEO vs LEO), fibre, cable and DOCSIS, DSL, cellular tethering vs hotspot, and WISPs.

Updated 23 Sept 2026Internet Connection Types

Professor Messer A+ 220-1201 objective 2.8 — crimpers, Wi-Fi and spectrum analysers, tone generator and probe, punch-down tools, cable testers, loopback plugs, taps and SPAN.

Updated 23 Sept 2026Network Tools

Professor Messer A+ 220-1201 objective 3.1 — LCD backlights, TN vs IPS vs VA, OLED, mini LED local dimming, digitizers and styluses, inverters and the torch test.

Updated 24 Sept 2026Display Types

Professor Messer A+ 220-1201 objective 3.1 — pixel density and PPI maths, refresh rate vs FPS and V-sync, resolution and aspect ratio, and colour gamut percentages.

Updated 24 Sept 2026Display Attributes

Professor Messer A+ 220-1201 objective 3.2 — twisted pair and why it is twisted, categories and distances, coax, UTP vs STP shielding codes, direct burial and plenum-rated cable.

Updated 24 Sept 2026Network Cables

Professor Messer A+ 220-1201 objective 3.2 — ANSI/TIA-568 and ISO/IEC 11801, the T568A and T568B pinouts, the four pins that differ, crimping checks and keystone jacks.

Updated 24 Sept 2026568A and 568B Colours

Professor Messer A+ 220-1201 objective 3.2 — light through core and cladding, ferrules and connectors, and multimode vs single-mode fibre on distance, source and core size.

Updated 24 Sept 2026Optical Fibre

Professor Messer A+ 220-1201 objective 3.2 — USB versions and speeds, connector types and USB-C, DB-9 serial, RS-232 console access, and Thunderbolt 1 to 4.

Updated 24 Sept 2026Peripheral Cables

Professor Messer A+ 220-1201 objective 3.2 — HDMI, DisplayPort and its locking connector, DVI variants and single/dual link, VGA, and video over USB-C.

Updated 24 Sept 2026Video Cables

Professor Messer A+ 220-1201 objective 3.2 — SATA revisions and speeds, the one-to-one power and data connectors, no daisy chaining, and eSATA.

Updated 24 Sept 2026Storage Cables

Professor Messer A+ 220-1201 objective 3.2 — DVI-D to HDMI and DVI-A to VGA compatibility, USB-to-Ethernet and USB-C-to-USB-A adapters, and USB hubs.

Updated 24 Sept 2026Adapters and Converters

Professor Messer A+ 220-1201 objective 3.2 — RJ11 and RJ45, F connectors and DOCSIS, punchdown blocks, USB and USB-C, Molex, Lightning, and DB-9/RS-232.

Updated 24 Sept 2026Copper Connectors

Professor Messer A+ 220-1201 objective 3.2 — ST bayonet, SC push-pull, and LC clip connectors for optical fibre, compared by mechanism and size.

Updated 24 Sept 2026Fiber Connectors

Professor Messer A+ 220-1201 objective 3.3 — RAM vs storage, DIMM and SO-DIMM, 64-bit data width, SDRAM, double data rate, and DDR3/DDR4/DDR5 compatibility and keying.

Updated 24 Sept 2026An Overview of Memory

Professor Messer A+ 220-1201 objective 3.3 — parity memory and even-parity calculation, ECC memory, memory bandwidth in MT/s, and multi-channel RAM.

Updated 24 Sept 2026Memory Technologies

Professor Messer A+ 220-1201 objective 3.4 — hard drives and RPM, SSDs, PCIe and NVMe, SAS, mSATA and M.2 keying, flash memory formats, and optical drives.

Updated 24 Sept 2026Storage Devices

Professor Messer A+ 220-1201 objective 3.4 — RAID 0 striping, RAID 1 mirroring, RAID 5 and RAID 6 parity, and nested RAID 1+0, plus why RAID is not backup.

Updated 24 Sept 2026RAID

Professor Messer A+ 220-1201 objective 3.6 — power supply safety, AC vs DC, amps/volts/watts, regional voltage, the 24-pin connector, redundant PSUs, modular cabling, sizing, and 80 PLUS efficiency.

Updated 24 Sept 2026Computer Power

A+ Core 1 3.5 — ATX vs micro-ATX vs Mini-ITX: size, slots, power (20/24-pin) and shared ATX mounting.

Updated 27 Sept 2026Motherboard Form Factors

A+ Core 1 3.5 — buses, PCI (parallel, 32/64-bit) vs PCIe (serial, lanes), keying, and safe card installation.

Updated 27 Sept 2026Motherboard Expansion Slots

A+ Core 1 3.5 — main and PCIe power connectors, SATA/eSATA, front-panel/USB/TPM headers, and M.2.

Updated 27 Sept 2026Motherboard Connections

A+ Core 1 3.5 — Intel vs AMD sockets, zero-force CPU install, and multisocket server motherboards.

Updated 27 Sept 2026Motherboard Compatibility

A+ Core 1 3.5 — BIOS firmware, POST and boot, legacy BIOS vs UEFI, dual-BIOS flash, and safe setting changes.

Updated 27 Sept 2026The BIOS

A+ Core 1 3.5 — entering setup, boot order, USB control, fans/temps, Secure Boot, boot vs supervisor passwords, CMOS reset, virtualisation.

Updated 27 Sept 2026BIOS Settings

A+ Core 1 3.5 — TPM (on-board crypto, root of trust, BitLocker) vs HSM (centralised keys and crypto offload).

Updated 27 Sept 2026HSM and TPM

A+ Core 1 3.5 — 32-bit vs 64-bit (x86/x64), ARM architecture, and multi-core CPUs.

Updated 27 Sept 2026CPU Features

A+ Core 1 3.5 — sound cards, integrated vs discrete GPUs, capture cards, NICs, and driver install best practice.

Updated 27 Sept 2026Expansion Cards

A+ Core 1 3.5 — fans and airflow, passive cooling, heat sinks, thermal paste vs pads, and liquid cooling.

Updated 27 Sept 2026Cooling

A+ Core 1 3.7 — MFD setup, drivers, PCL/PostScript, connectivity, sharing, print features, secure printing, and scanning.

Updated 27 Sept 2026Multifunction Devices

A+ Core 1 3.8 — laser imaging process, toner/OPC drum, cartridge and maintenance-kit replacement, calibration, and safe cleaning.

Updated 27 Sept 2026Laser Printer Maintenance

A+ Core 1 3.8 — inkjet operation, CMYK cartridges, print heads, feed rollers, duplex, plus carriage/belt and calibration.

Updated 27 Sept 2026Inkjet Printers

A+ Core 1 3.8 — cleaning inkjet print heads, replacing CMYK cartridges, calibration, and clearing paper jams.

Updated 27 Sept 2026Inkjet Printer Maintenance

A+ Core 1 3.8 — how thermal printers work, the feed assembly and heating element, thermal paper, and handling output safely.

Updated 27 Sept 2026Thermal Printers

A+ Core 1 3.8 — replacing thermal paper, cleaning the heating element with IPA, removing debris safely, and heat/fade sensitivity.

Updated 27 Sept 2026Thermal Printer Maintenance

A+ Core 1 3.8 — dot-matrix print heads, ribbons, tractor-feed paper, green bar paper, and multi-part carbonless copies.

Updated 27 Sept 2026Impact Printers

A+ Core 1 3.8 — ribbon replacement, print head replacement, and continuous tractor-feed paper handling on dot-matrix printers.

Updated 27 Sept 2026Impact Printer Maintenance

The Linux Command Line ch. 1 — shell vs terminal, reading the prompt, history and editing keys, copy and paste, and your first commands.

Updated 18 Sept 2026Ch. 1

The Linux Command Line ch. 2 — the single directory tree, pwd, ls and cd, absolute vs relative paths, shortcuts, and the rules for filenames.

Updated 18 Sept 2026Ch. 2

The Linux Command Line ch. 3 — ls options and the long listing, command syntax, identifying files with file, paging with less, and a tour of the directory tree.

Updated 18 Sept 2026Ch. 3

The Linux Command Line ch. 4 — wildcards and character classes, mkdir, cp, mv and rm with their key options, and hard vs symbolic links.

Updated 18 Sept 2026Ch. 4

The Linux Command Line ch. 5 — the four kinds of command, type and which, help, man, apropos, whatis and info, and making your own aliases.

Updated 18 Sept 2026Ch. 5

TLCL chapter 6 — stdin/stdout/stderr, > >> 2> &> and 2>&1 ordering, /dev/null, group commands, pipelines, and the filters uniq, wc, grep, head, tail and tee.

Updated 23 Sept 2026Ch. 6

TLCL chapter 7 — pathname, tilde, arithmetic, parameter and command expansion, plus double quotes, single quotes and backslash escaping.

Updated 24 Sept 2026Ch. 7

TLCL ch. 8 — readline cursor movement/editing, kill and yank, tab completion, and command history/expansion.

Updated 27 Sept 2026Ch. 8

TLCL ch. 9 — users/groups/other, read/write/execute, chmod, umask, special permissions, su/sudo, chown/chgrp, and passwd.

Updated 27 Sept 2026Ch. 9

Month of Lunches ch. 1 — why PowerShell matters, Windows PowerShell 5.1 vs PowerShell 7, installing and verifying PS7, lab setup, and how to study the book.

Updated 20 Sept 2026Ch. 1

Month of Lunches ch. 2 — engine vs host, console/Windows Terminal/VS Code, console setup, tab completion, PSReadLine history and predictions, and running elevated.

Updated 20 Sept 2026Ch. 2

Month of Lunches ch. 3 — Update-Help/Save-Help, finding commands with Get-Command, reading syntax and parameter sets, Get-Help options, about_ topics, and -WhatIf/-Confirm.

Updated 20 Sept 2026Ch. 3

Month of Lunches ch. 4 — command anatomy, Verb-Noun naming and approved verbs, cmdlet/function/alias/application, aliases cross-platform, shortcuts, external commands, errors, execution policy.

Updated 20 Sept 2026Ch. 4

PowerShell providers and PSDrives — what they are, the built-in list, filesystem-style navigation, registry keys vs properties, and wildcards vs -LiteralPath.

Updated 24 Sept 2026Ch. 5

PowerShell's object pipeline — Export-Csv vs Export-Clixml, Out-File and Out-Printer, ConvertTo-Html, Stop-Process/Stop-Service safety, and common pipeline mistakes.

Updated 24 Sept 2026Ch. 6

MoL ch. 7 — management shells, snap-ins vs modules, module discovery/import, profile scripts, and the PowerShell Gallery.

Updated 27 Sept 2026Ch. 7

MoL ch. 8 — what objects are, Get-Member, properties and methods, Sort-Object, Select-Object, and format-last discipline.

Updated 27 Sept 2026Ch. 8

Lucas, Networking for System Administrators (2nd ed.) ch. 1 — the four layers, encapsulation, what changes at each hop, and troubleshooting commands by layer.

Updated 22 Sept 2026Ch. 1

Lucas, Networking for System Administrators (2nd ed.) ch. 2 — interfaces, autonegotiation, MTU and DF ping, ARP and NDP, VLAN terms and datalink error counters.

Updated 22 Sept 2026Ch. 2

Networking for Sysadmins ch. 3 — IPv4 addressing, subnets/netmasks, viewing config on Windows/Debian/FreeBSD, private addressing/NAT, and troubleshooting.

Updated 27 Sept 2026Ch. 3