PhilNITS IT Passport cheat sheet

Binary prefixes: 1 KiB = 2^10 = 1024 bytes; 1 MiB = 2^20 bytes; 1 GiB = 2^30 bytes; 1 TiB = 2^40 bytes. Decimal prefixes use powers of 1000.

Bits and bytes: 1 byte = 8 bits. Character codes: ASCII uses 7 bits (128 codes); Shift_JIS handles Japanese; Unicode/UTF-8 covers multiple languages.

Number bases: binary 0b, octal 0o, hexadecimal 0x. Convert by grouping 4 bits per hex digit. Negative integers use two's complement: invert bits and add 1.

Logic gates: AND outputs 1 only if all inputs are 1; OR outputs 1 if any input is 1; XOR outputs 1 when inputs differ; NOT inverts. Half adder: sum = XOR, carry = AND.

CPU components: control unit (fetches and decodes instructions), ALU (arithmetic and logic), registers (program counter, accumulator). Clock frequency in Hz sets cycle timing.

Storage hierarchy by speed and cost: registers > cache > main memory > SSD/HDD > optical/tape. Volatile memory (DRAM) loses data on power loss; flash and HDD are non-volatile.

RAID rules: RAID 0 stripes with no redundancy; RAID 1 mirrors; RAID 5 stripes with distributed parity and tolerates one disk failure; RAID 6 tolerates two.

Network models: OSI has 7 layers (physical, data link, network, transport, session, presentation, application); TCP/IP has 4. TCP is connection-oriented and reliable; UDP is connectionless.

IP addressing: IPv4 is 32 bits, IPv6 is 128 bits. A /24 prefix has 256 addresses. Private ranges include 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.

SWOT separates internal factors (Strengths, Weaknesses) from external factors (Opportunities, Threats); it is an analysis tool, not a decision rule by itself.

Three Cs framework compares Company, Customers, and Competitors when setting positioning. Porter's Five Forces covers rivalry, new entrants, substitutes, supplier power, and buyer power.

Porter's generic strategies: cost leadership, differentiation, and focus. A firm combining low cost and broad differentiation risks being stuck in the middle.

Product portfolio (BCG matrix): stars (high growth, high share), cash cows (low growth, high share), question marks (high growth, low share), dogs (low growth, low share).

Break-even point in units = fixed costs / (unit price - variable cost per unit). Contribution margin per unit is price minus variable cost per unit.

NPV discounts future cash flows at the cost of capital; accept a project when NPV > 0. IRR is the discount rate at which NPV = 0; accept when IRR exceeds the hurdle rate.

Payback period = time until cumulative cash inflow equals the initial investment; it ignores cash flows after payback and the time value of money.

RFM analysis scores customers on Recency, Frequency, and Monetary value. The 80/20 rule (Pareto principle) states roughly 20% of causes produce 80% of results.

IT governance frameworks: COBIT governs IT processes; ITIL covers IT service management lifecycle; ISO/IEC 27001 specifies information security management system requirements.

Project management triple constraint: scope, time, and cost, with quality affected by changes to any of the three. A change in one typically forces adjustment in another.

WBS (work breakdown structure) decomposes deliverables hierarchically. A milestone is a zero-duration checkpoint; the critical path is the longest path and sets the shortest project duration.

Earned value: CV = EV - AC (negative means over budget); SV = EV - PV (negative means behind schedule); CPI = EV/AC; SPI = EV/PV.

Risk response types: avoid, transfer (e.g., insurance, outsourcing), mitigate, and accept. A risk is an uncertain event; an issue is a problem that has already occurred.

IT service management: an incident interrupts or degrades a service and is restored quickly; a problem is the underlying root cause. A change request follows change management approval.

SLA (service level agreement) defines service levels between provider and customer; OLA is an internal agreement supporting the SLA; KPI is a measurable indicator of performance.

Security management: the CIA triad is Confidentiality, Integrity, and Availability. Authentication verifies identity; authorization grants permissions; accounting/audit logs record activity.

Access control: least privilege grants only needed rights; need-to-know limits data access. Multi-factor authentication combines something you know, have, and are.

Legal and compliance: a nondisclosure agreement protects confidential information; personal data protection laws require purpose limitation, consent, and secure handling of personal information.