MSCE Computer Studies cheat sheet

Every computer implements the input → process → output → storage (IPO+S) cycle; the same model describes a mainframe, a laptop and a smartphone.

Generations: 1st vacuum tubes (ENIAC, 1946); 2nd transistors (late 1950s); 3rd integrated circuits (mid-1960s); 4th microprocessors (Intel 4004, 1971); 5th AI, parallel processing and quantum research.

Classification by size, from largest to smallest: supercomputer, mainframe, minicomputer/midrange, microcomputer; by data handled: analog, digital, hybrid.

Analog computers measure continuous physical quantities (voltage, temperature); digital computers count discrete binary values; hybrid computers combine both, as in patient monitors.

Charles Babbage's Analytical Engine (1837) introduced the stored-program idea; Ada Lovelace wrote the first published algorithm for it; the Turing machine (1936) formalised what is computable.

Von Neumann architecture: one memory holds both instructions and data, with CPU, memory and I/O linked by buses, so programs can be loaded without rewiring.

Capacity units: 1 byte = 8 bits; 1 KiB = 1024 bytes, 1 MiB = 1024 KiB; storage vendors often use decimal multiples (1 GB = 1000 MB), which explains smaller-than-advertised capacities.

Performance measures: clock speed in hertz (GHz), MIPS for instruction throughput, FLOPS for floating-point work, and benchmark scores for mixed workloads.

CPU = Control Unit + ALU + registers; the fetch–decode–execute cycle repeats until a halt instruction or interrupt.

Key registers: PC (next instruction address), IR (current instruction), MAR (address being accessed), MBR/MDR (data being transferred), accumulator (ALU results).

Memory hierarchy by speed and cost per bit, fastest first: registers → L1/L2/L3 cache → RAM → SSD/HDD → optical/tape backup.

SRAM uses flip-flops, is fast and costly, and serves as cache; DRAM uses capacitors, needs periodic refresh, and forms main memory; both are volatile.

Addressable memory = 2^n locations for an n-bit address bus, so a 32-bit address bus addresses 2^32 bytes = 4 GiB.

Optical capacities (single layer): CD 700 MB, DVD 4.7 GB, Blu-ray 25 GB; read/write speeds are quoted as multiples of 1× (150 KB/s for CD).

HDD access time = seek time + rotational latency + transfer time; SSD access has no mechanical delay, so random reads are far faster.

Input devices convert human or environmental data into digital signals (keyboard, scanner, sensor); output devices convert digital data into human-usable form (monitor, printer, plotter); a touchscreen is both.

System software (operating system, utilities, device drivers, firmware) runs and maintains the machine; application software performs user tasks.

Core OS functions: process scheduling, memory management, file-system management, device I/O control, security/access control and the user interface.

OS types: batch, multiprogramming, multitasking, time-sharing, real-time (hard vs soft), distributed, embedded, mobile and network operating systems.

Scheduling rules: FCFS is simple but suffers convoy effect; SJF minimises average waiting time but starves long jobs; round robin is preemptive with a fixed time quantum; priority scheduling may need ageing to avoid starvation.

A context switch saves the running process's state in its Process Control Block (PCB) and loads another's; it is pure overhead.

Virtual memory maps pages to frames; a page fault loads a missing page from disk; continuous faulting that leaves no time for work is thrashing, curbed by working-set control.

Firmware is stored in ROM/flash (e.g., BIOS/UEFI); drivers translate generic OS calls into device-specific commands.

Licensing: proprietary (closed source, licensed), open source (source code available under a licence), freeware (free but closed), shareware (trial then pay).

Positions carry weights base^position, numbered from 0 at the right: 1011₂ = 1×8 + 0×4 + 1×2 + 1×1 = 11₁₀.

Decimal → base n: divide repeatedly by n and read the remainders bottom-up; e.g., 45 ÷ 2 gives 101101₂.

Binary → octal: group bits in threes from the right; binary → hex: group in fours. Example: 1101 1010₂ = DA₁₆ = 332₈.

Unsigned 8-bit range is 0–255; signed two's complement 8-bit range is −128 to +127; the leftmost bit is the sign bit.

Two's complement of a value: invert every bit, then add 1; subtraction A − B is performed as A + (two's complement of B).

Character codes: ASCII is 7-bit (128 codes); extended ASCII is 8-bit (256); Unicode (UTF-8/UTF-16) covers all writing systems; EBCDIC is a legacy IBM 8-bit code.

BCD stores each decimal digit in its own 4-bit group, used in calculators and digital displays where decimal accuracy matters.

Size formulas: bitmap bytes = width × height × colour depth ÷ 8; sampled sound bytes = sample rate × bit depth ÷ 8 × channels × seconds.

Spreadsheet references: A1 relative (changes when copied), $A$1 absolute (fixed), $A1 and A$1 mixed (one part fixed); formulas always begin with =.

Common spreadsheet errors: #DIV/0! division by zero, #REF! deleted reference, #VALUE! wrong data type, #NAME? unrecognised function name.

Core spreadsheet functions: SUM, AVERAGE, COUNT/COUNTA, MAX/MIN, IF(condition, true, false), VLOOKUP, and COUNTIF/SUMIF for conditional totals.

Word processing: styles enforce consistent formatting, mail merge pairs a main document with a data source, track changes records edits, and tables of contents build from heading styles.

Relational database vocabulary: table = file, record = row, field = column; the primary key uniquely identifies a record and cannot be null or duplicated.

A foreign key is a field in one table holding the primary-key value of another table, creating the link used for referential integrity.

Normalisation: 1NF removes repeating groups (atomic values), 2NF removes partial dependencies on part of a composite key, 3NF removes transitive dependencies on non-key fields.

Presentation software: slide master controls global layout; transitions apply between slides, animations apply to objects within a slide; notes aid the presenter, handouts aid the audience.

Topologies: star (central switch, single point of failure at the hub), bus (shared backbone, collision-prone), ring (token or dual-ring), mesh (redundant paths, costly), hybrid.

Scale terms: PAN (personal, metres), LAN (building/campus), MAN (city), WAN (countries); the internet is the largest WAN.

OSI seven layers, bottom-up: Physical, Data Link, Network, Transport, Session, Presentation, Application; TCP/IP collapses these into Network Access, Internet, Transport, Application.

IPv4 is 32-bit dotted decimal; IPv6 is 128-bit hexadecimal. Private IPv4 ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 - not routed on the public internet.

Default ports: HTTP 80, HTTPS 443, FTP 21, SMTP 25, POP3 110, IMAP 143, DNS 53, DHCP 67/68.

Devices: hub repeats to all ports, switch forwards by MAC address, router forwards by IP address between networks, gateway translates between protocols, firewall filters traffic, modem modulates/demodulates.

Media: twisted pair (Cat5e/Cat6, cheap, ~100 m limit), coaxial, fibre optic (light, long haul, immune to EMI), wireless (radio, microwave, satellite).

Bandwidth is capacity (Mbps), latency is delay (ms); packet switching splits messages into independently routed packets, reassembled at the destination.

A valid algorithm must be finite, definite (unambiguous), effective, and have zero or more inputs with one or more outputs.

Flowchart symbols: oval for start/stop, parallelogram for input/output, rectangle for process, diamond for decision, arrow for flow direction.

Three control structures: sequence, selection (IF…THEN…ELSE, CASE) and iteration (FOR count-controlled, WHILE and REPEAT…UNTIL condition-controlled).

Searching: linear search is O(n) and works on unsorted data; binary search is O(log n) but requires data sorted in order.

Sorting: bubble/insertion/selection are O(n²); merge sort is O(n log n) in all cases; quicksort averages O(n log n) but degrades to O(n²) on bad pivots.

Compiler translates the whole program before running and reports all syntax errors; interpreter translates and executes line by line, easing debugging but running slower.

Error types: syntax (breaks language rules, caught at translation), runtime (e.g., division by zero), logic (program runs but gives wrong output).

Operators and precedence: brackets, then exponentiation, then *, /, then +, −, then relational (<, >, =), then logical (NOT, AND, OR); a function returns a value, a procedure does not.

An information system combines people, hardware, software, data, networks and procedures; system types include TPS (routine transactions), MIS (summary reports), DSS (what-if analysis) and EIS (executive dashboards).

SDLC phases: planning/feasibility, analysis, design, implementation, testing, deployment, maintenance; waterfall is sequential, iterative/agile repeats cycles.

CIA triad: confidentiality (secrecy), integrity (accuracy and completeness), availability (access when needed).

Malware: virus attaches to a host file, worm self-replicates across networks, trojan disguises as legitimate software, ransomware encrypts data for payment, spyware secretly collects activity.

Symmetric encryption uses one shared secret key (fast); asymmetric uses a public/private key pair (solves key distribution); hashing (SHA-256) verifies integrity but is not reversible.

Defences: strong authentication (knowledge, token, biometric), least-privilege authorisation, firewalls, antivirus, patching, encryption, and backups (full, incremental, differential).

Ethical and legal issues: software piracy and licensing breaches, copyright and plagiarism, data-protection/privacy law, acceptable-use policies, and responsible disclosure of vulnerabilities.

Social impact: digital divide, automation-driven job change, e-waste and energy use (green computing), ergonomics and repetitive strain injury, and screen-time/cyberbullying concerns.