Data Representation, Encoding, and Translation Concepts

Vocabulary flashcards covering key concepts from encoding schemes, memory units, and translation processes described in the lecture notes.

Bit

The most basic unit of information in computing, representing either 0 or 1.

Nibble

4 bits; a half-byte that can encode 16 values.

Byte

8 bits; the basic addressable unit of memory in many systems.

Word

A fixed number of bytes used by a CPU to store instructions and data (commonly 4 or 8 bytes).

ASCII

American Standard Code for Information Interchange; a 7-bit character encoding with 128 characters.

EBCDIC

IBM’s proprietary 8-bit character encoding; historically hindered data interchange.

Unicode

A modern character encoding that supports many languages; ASCII is contained within Unicode.

ASCII as a subset of Unicode

All ASCII characters (0–127) are included in Unicode, making ASCII a subset of Unicode.

Binary

Base-2 numeral system using digits 0 and 1; each position is a power of two.

Decimal

Base-10 numeral system using digits 0–9; the system we use every day.

Hexadecimal

Base-16 numeral system using digits 0–9 and A–F; two hex digits represent one byte.

Core dump

An OS-provided dump of a program’s memory contents after a crash, used for debugging.

Machine language

Binary instructions executed directly by the CPU; the native language of the computer.

Assembler

A translator that converts assembly language mnemonics into machine code; one-to-one with machine instructions.

Assembly language

A human-readable representation of machine instructions using mnemonics and labels.

High-level language

Languages like Java, C++, and C# that are closer to human language and require translation to machine code.

Compiler

A program that translates high-level code into machine code or intermediate form, producing executables.

Interpreter

A program that executes source code directly or translates and runs it line-by-line; generally slower than compiling.

Java hybrid approach

Java compiles to bytecode (intermediate, platform-independent); the JVM executes the bytecode and may JIT-compile parts.

Token

A small meaningful unit of source code (identifiers, literals, operators, etc.).

Syntax analyzer (parser)

A component that checks token sequences for correct structure and order in a program.

Symbol table

A data structure mapping identifiers (names) to memory locations and metadata like type and scope.

Declaration

A statement that introduces a new variable or function and its type.

Initialization

Assigning an initial value to a variable at the point of declaration or later.

Identifier

A name used for variables, methods, or classes; case-sensitive and not allowed to start with a digit or be a reserved word.

Reserved words

Keywords with special meaning in a language (e.g., class, int, if, else).

Primitive data type

Built-in value types stored by value (e.g., int, long, float, double, char, boolean, byte, short).

Reference data type

Stores a reference (address) to an object rather than the value itself (e.g., String).

Byte, short, int, long

Java integer primitives: byte (1 byte), short (2 bytes), int (4 bytes, default), long (8 bytes).

Float, double

Floating-point primitives: float (4 bytes) and double (8 bytes; default for decimal literals).

Char

Character primitive type in Java; typically 2 bytes (Unicode).

Boolean

Boolean primitive type that can hold true or false.

Literal

A value written directly in source code (e.g., 67, 55.5, 'A').

Assignment

The equals sign (=) operator that stores the value of the right-hand side into the left-hand variable.

Suffixes for literals

Letters appended to numeric literals to specify type (e.g., 88.4f for float, 100L for long).

Two's complement

Binary representation used for signed integers; negative numbers are stored using two's complement.

Memory display formats

Memory contents can be shown in binary, decimal, or hexadecimal; hex is common, with two hex digits per byte.

Tokenization

The process of breaking source code into tokens (identifiers, literals, operators).

Bytecode

Java’s intermediate, platform-independent code stored in .class files.

JVM (Java Virtual Machine)

Executes Java bytecode and may perform Just-In-Time compilation for efficiency.

Translation steps

Compiler pipeline: source code → tokens → syntax analysis → intermediate code → optimization → target code (machine language).