FTCE Computer Science flashcards

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

Two's complement negation

To negate an n-bit value, invert every bit and add one. This representation gives a signed range from negative two to the power n minus one up to positive two to the power n minus one minus one.

Hexadecimal byte rendering

Each hexadecimal digit maps to exactly four binary bits, so any single byte is written as precisely two hex digits. Decimal 255 becomes FF, and decimal 16 becomes 10.

Stack versus queue

A stack removes the most recently added item first, supporting push and pop. A queue removes the oldest item first, supporting enqueue and dequeue, and drives breadth-first search.

Hash table average complexity

With a good hash function and low load factor, lookup, insertion, and deletion average constant time. Under heavy collisions all keys may chain into one bucket, degrading to linear time.

Compiler versus interpreter

A compiler translates the entire source program into machine code before any execution, reporting all syntax errors together. An interpreter translates and runs one statement at a time.

Quicksort worst case

Quicksort partitions around a pivot, averaging n log n comparisons. When the pivot is consistently the smallest or largest element, as with sorted input, it degrades to quadratic time.

Method overloading versus overriding

Overloading declares several methods with the same name but different parameter lists, resolved at compile time. Overriding redefines an inherited method with an identical signature, resolved at runtime.

De Morgan's laws

The negation of a conjunction equals the disjunction of the negations, and the negation of a disjunction equals the conjunction of the negations. These laws simplify Boolean expressions and gate circuits.

Algorithm defining properties

A valid algorithm must terminate after finitely many steps, consist of definite unambiguous instructions, accept input and produce output, and have every step effectively executable.

Binary search precondition

Binary search repeatedly halves a sorted array, comparing the target to the middle element, and runs in logarithmic time. It requires sorted data and efficient random access by index.

Big-O simplification rule

Big-O notation keeps only the fastest-growing term and discards constant factors. So three n squared plus five n plus seven simplifies to O of n squared.

Recursion base case

Every recursive method needs a base case that returns without calling itself, plus a recursive case whose argument moves toward that base. Without a base case, calls exhaust the stack.

Flowchart decision symbol

A diamond represents a decision, with one arrow leaving for true and another for false. Rectangles show processes, parallelograms show input or output, and ovals mark start and end.

Off-by-one loop error

An off-by-one error executes a loop one time too many or too few, often from using less-than versus less-than-or-equal. Tracing variable values per iteration exposes it.

Boundary test values

Boundary testing checks the edges of valid input, such as the first and last array index, zero, and the maximum allowed value, because errors cluster at those limits.

Pass by value

When arguments are passed by value, the method receives a copy, so reassigning the parameter never changes the caller's variable. Passing an object reference copies the reference, not the object.

Java string equality

The double-equals operator on Java strings compares object references, not characters. The equals method compares character content, so it is the correct test for equal text.

Try catch finally

A try block holds code that may throw, catch blocks handle matching exception types, and the finally block always executes, typically releasing files or connections.

SDLC maintenance phase

After deployment, maintenance fixes defects, adapts software to changed requirements, and optimizes performance. It usually consumes the largest portion of total lifetime cost.

Local variable scope

A local variable is declared inside a method or block and exists only while that block executes. Parameters behave as locals, while static variables persist for the program's lifetime.

Version control merge conflict

A conflict occurs when two branches change the same lines of a file. The tool marks both versions, and a developer must edit the file to resolve them before committing.

Agile versus waterfall

Agile delivers working increments in short repeated iterations with continuous customer feedback. Waterfall completes requirements, design, implementation, testing, and deployment in strict sequence.

Fetch decode execute cycle

The processor fetches an instruction from the address in the program counter, decodes its operation, executes it, and stores any result, then advances to the next instruction.

Volatile versus nonvolatile memory

Volatile memory such as RAM loses its contents when power is removed and holds running programs. Nonvolatile memory such as ROM and disk storage retains data without power.

Memory hierarchy ordering

From fastest and smallest to slowest and largest: registers, cache levels, main memory, then solid-state or magnetic storage. Higher levels cost more per byte but reduce access latency.

Operating system core duties

An operating system schedules processes, allocates memory, manages files and devices through drivers, and enforces user accounts and access permissions for running applications.

Signed byte range

An eight-bit signed integer using two's complement spans negative 128 through positive 127. Computing a sum outside that range causes overflow, which wraps or raises an error.

ASCII versus Unicode

ASCII encodes 128 characters in seven bits, covering English letters, digits, and basic symbols. Unicode assigns code points to every writing system, and UTF-8 stores them in one to four bytes.

OSI transport layer

Layer four of the OSI model carries end-to-end segments between applications. TCP provides reliable ordered delivery with acknowledgments, while UDP sends datagrams without guarantees.

DNS and DHCP roles

DNS translates human-readable domain names into IP addresses. DHCP automatically assigns IP addresses, subnet masks, and default gateways to devices joining a network.

Private IPv4 address ranges

Non-routable private ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. A /24 subnet uses mask 255.255.255.0 and provides 254 usable host addresses.

Star versus mesh topology

In a star topology every device connects to a central switch, so one cable failure isolates one node but the switch is a single point of failure. Mesh adds redundant paths at higher cost.