PhilNITS FE cheat sheet

Two's complement: to negate a k-bit integer, invert all bits and add 1; range is -2^(k-1) to 2^(k-1)-1. Overflow in signed addition occurs when two operands of the same sign produce a result of the opposite sign.

IEEE 754 single precision: 1 sign bit, 8 exponent bits with bias 127, 23 fraction bits; value = (-1)^S × 1.F × 2^(E-127) for normalized numbers. Double precision uses 11 exponent bits (bias 1023) and 52 fraction bits.

TCP vs UDP: TCP provides connection setup (3-way handshake), ordered delivery, retransmission, and flow/congestion control; UDP is connectionless with no delivery guarantee. Ports 0-1023 are well-known, 1024-49151 registered, 49152-65535 dynamic/ephemeral.

IPv4 address classes: A 1-126 (default mask /8), B 128-191 (/16), C 192-223 (/24); 127 is loopback. Subnet host count = 2^(32-prefix) - 2. CIDR /26 gives 62 usable hosts per subnet.

Relational algebra: selection σ, projection π, Cartesian product ×, natural join ⋈, union ∪, difference −, rename ρ. SQL execution order is FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY; HAVING filters groups, WHERE filters rows.

Normalization: 1NF removes repeating groups; 2NF removes partial dependencies on a composite key; 3NF removes transitive dependencies on non-key attributes; BCNF requires every determinant to be a superkey.

OS scheduling: FCFS is non-preemptive; SJF minimizes average waiting time but can starve long jobs; Round Robin uses a time quantum; priority scheduling can cause starvation, mitigated by aging. Deadlock requires mutual exclusion, hold-and-wait, no preemption, and circular wait simultaneously.

Software testing levels: unit → integration → system → acceptance. Black-box techniques include equivalence partitioning and boundary value analysis; white-box coverage includes statement, branch, and condition coverage. Regression testing verifies that changes did not break existing behavior.

Algorithm complexity: binary search O(log n) on sorted data; merge sort O(n log n) worst case; quicksort O(n log n) average, O(n^2) worst; hash table lookup O(1) average. Big-O describes an upper bound on growth, not exact runtime.

Porter's Five Forces: rivalry among existing competitors, threat of new entrants, threat of substitutes, bargaining power of buyers, bargaining power of suppliers. High force intensity generally lowers industry profitability.

SWOT analysis classifies internal Strengths and Weaknesses and external Opportunities and Threats; it is a situational assessment, not a prioritized action plan.

Three generic strategies (Porter): cost leadership, differentiation, and focus (cost focus or differentiation focus). A firm stuck between strategies without a clear advantage risks lower returns.

BCG matrix axes: market growth rate (vertical) and relative market share (horizontal). Quadrants are stars (high growth, high share), cash cows (low growth, high share), question marks (high growth, low share), and dogs (low growth, low share).

Product life cycle stages: introduction, growth, maturity, decline. Pricing often shifts from skimming or penetration at introduction to competitive pricing at maturity.

Break-even point in units = fixed costs ÷ (unit price − unit variable cost). Contribution margin per unit is unit price minus unit variable cost; margin ratio = contribution margin ÷ sales.

NPV = Σ [CF_t ÷ (1+r)^t] − initial investment; accept projects with NPV > 0. IRR is the discount rate at which NPV = 0; a project is acceptable when IRR exceeds the cost of capital.

Ansoff growth matrix: market penetration (existing product, existing market), market development (existing product, new market), product development (new product, existing market), diversification (new product, new market).

IT governance frameworks: COBIT links business goals to IT controls; ITIL structures service management practices; balanced scorecard perspectives are financial, customer, internal process, and learning and growth.

Project management triangle: scope, time, and cost are constraints; quality is affected when one constraint changes. A change in scope normally requires adjustment to schedule or resources.

Critical path method: the critical path is the longest sequence of dependent activities and determines minimum project duration; activities on it have zero total float.

Earned value: EV = budgeted cost of work performed; PV = planned value; AC = actual cost. CV = EV − AC, SV = EV − PV, CPI = EV ÷ AC, SPI = EV ÷ PV. CPI < 1 means over budget.

Risk response strategies: for threats - avoid, transfer, mitigate, accept; for opportunities - exploit, share, enhance, accept. A risk register records probability, impact, owner, and response.

RACI matrix assigns Responsible (does the work), Accountable (final authority, one per task), Consulted (two-way input), and Informed (one-way updates).

Service management (ITIL): incident restores service quickly; problem finds root cause; change management controls modifications; SLA defines agreed service levels between provider and customer.

Information security triad CIA: confidentiality (encryption, access control), integrity (hashing, checksums), availability (redundancy, backups). Least privilege and separation of duties are preventive controls.

Personal information protection: purpose limitation, consent, data minimization, and retention limits are common principles; a data breach typically triggers notification duties to authorities and affected individuals.

Team development stages (Tuckman): forming, storming, norming, performing, adjourning. A project manager shifts from directive to delegating leadership as the team matures.