NYSTCE Computer Science flashcards

34 cards. Read the term and the definition here. The deck at the top of this page is optional.

Big-O of binary search

O(log n), because each comparison halves the remaining search interval; the input array must be sorted before searching.

Stack vs queue order

A stack is last-in-first-out (LIFO), removing the most recently added item; a queue is first-in-first-out (FIFO), removing the oldest item.

Hash table average complexity

Average-case O(1) for insert, search, and delete when the hash function distributes keys well; worst case is O(n) with heavy collisions.

BFS versus DFS

Breadth-first search explores level by level with a queue and finds shortest unweighted paths; depth-first search goes deep first using a stack or recursion.

Dijkstra algorithm requirement

All edge weights must be non-negative; with a binary heap the running time is O(E log V), and negative edges require Bellman-Ford instead.

Recursion base case

A condition that stops recursive calls without further recursion; without it the call stack grows until a stack overflow error occurs.

Value versus reference types

Value types store the data directly and copy on assignment; reference types store an address, so assignment copies the reference and both names share one object.

Short-circuit evaluation

In A && B, B runs only when A is true; in A || B, B runs only when A is false. This prevents unnecessary or unsafe evaluation.

Integer division and modulo

Integer division discards the fractional part (7/2 gives 3); modulo returns the remainder (7%2 gives 1) and can be negative for negative operands.

Compile-time vs run-time errors

Compile-time errors are syntax or type violations caught before execution; run-time errors such as division by zero occur while the program runs.

Variable scope and shadowing

Scope is the region where a name is visible; a local variable with the same name as a field shadows the field inside that block.

Unit versus integration testing

A unit test exercises one method or class in isolation; an integration test verifies that multiple components work together correctly.

For-to-while loop conversion

Move the initialization before the loop, keep the condition in the while header, and place the update at the end of the body.

n-bit value range

Unsigned n bits span 0 to 2^n minus 1; two's complement signed n bits span negative 2^(n-1) to 2^(n-1) minus 1.

Two's complement negation

Invert every bit of the number and add one; the leading bit has weight negative 2^(n-1), which makes subtraction use the same adder as addition.

Hex and binary grouping

Each hexadecimal digit maps to exactly four binary bits and each octal digit to three; group from the right to convert binary to hex.

ASCII versus Unicode

ASCII defines 128 seven-bit codes for basic Latin characters; Unicode assigns code points for all scripts, and UTF-8 encodes them in one to four bytes.

Fetch-decode-execute cycle

The CPU fetches the instruction at the program counter, decodes its opcode, executes it, writes results back, and advances the program counter.

Von Neumann bottleneck

Instructions and data share one memory and bus, so the processor waits for memory transfers; Harvard architecture separates the two memories to reduce this.

Cache locality

Temporal locality means recently used data is reused soon; spatial locality means nearby addresses are accessed soon. Cache exploits both to cut average memory latency.

Half adder outputs

Sum equals A XOR B and carry equals A AND B; a full adder also accepts a carry-in and combines two half adders with an OR gate.

OSI layer order

Physical, Data Link, Network, Transport, Session, Presentation, Application from layer one to seven; TCP/IP merges these into Link, Internet, Transport, and Application.

TCP versus UDP

TCP is connection-oriented and reliable with handshake, sequencing, and retransmission; UDP is connectionless and unreliable but has lower overhead and latency.

IPv4 versus IPv6 length

IPv4 addresses are 32 bits written as four decimal octets; IPv6 addresses are 128 bits written as eight hexadecimal groups.

Subnet host count

A /24 mask leaves 8 host bits, giving 2^8 minus 2, or 254 usable hosts, after reserving the network and broadcast addresses.

DNS, DHCP, and ARP

DNS maps names to IP addresses, DHCP assigns IP configuration automatically, and ARP resolves an IP address to a MAC address on the local link.

Symmetric versus asymmetric encryption

Symmetric encryption uses one shared secret key and is fast; asymmetric encryption uses a public/private key pair and supports signatures and key exchange.

Hashing versus encryption

A cryptographic hash is one-way and used to verify integrity; encryption is reversible with a key and used to protect confidentiality.

SQL injection mitigation

Use parameterized queries or prepared statements and validate input, so user data is treated as values rather than executable SQL code.

Digital divide

Unequal access to devices, reliable broadband, and digital literacy across income, geography, age, or disability groups, affecting participation in school and work.

Net neutrality

The principle that internet service providers treat all traffic equally, without blocking, throttling, or paid prioritization of specific content.

FERPA, COPPA, and HIPAA

FERPA protects student education records, COPPA limits data collection from children under 13, and HIPAA safeguards protected health information.

Permissive versus copyleft licenses

MIT and BSD allow reuse with few conditions; GPL is copyleft and requires derivative works distributed publicly to remain under the same open license.

Algorithmic bias

Systematically unfair model outcomes caused by biased training data, flawed labels, or design choices that disadvantage particular groups.