Variable

A variable is a named location that holds a value.

Related concepts:  NameValueAssignment

Closest Wikipedia entry:  Variable (computer science) — In computer programming, a variable is an abstract storage location paired with an associated symbolic name, which contains some known or unknown quantity of data or object referred to as a value; or in simpler terms, a variable is a named container for a particular set of bits or type of data (like integer, float, string, etc...). A variable can eventually be associated with or identified by a memory address. The variable name is the usual way to reference the stored value, in addition to referring to the variable itself, depending on the context.

Misconceptions about Variable

37 documented Misconceptions

AssignmentCopiesObject — Java

Assignment copies the object

AssignmentCopiesObject — JavaScript

Assignment copies the object

AssignmentCopiesObject — Python

Assignment copies the object

CallerFrameContainsCalleeFormal — Java

Stack frame of caller includes variables for callee's formal parameters

ConstDeclarationCanBeLeftUninitialized — JavaScript

Declarations of constants do not need to be immediately initialized

ControlledLocalAccess — Java

One can control access to local variables using access modifiers

ExpressionAssigns — Java

An expression that reads a variable also updates its value after the evaluation

ExpressionAssigns — Scratch

An expression that reads a variable also updates its value after the evaluation

ForEachIteratesOverIndices — Java

An enhanced for loop iterates over the indices of an array or a collection

ForEachVariableIsElement — Java

One can assign to the variable of an enhanced for statement to store a value in the corresponding array or collection element

ForVariableScopeBeyondLoop — Java

The scope of variables declared in a for loop header extends beyond the loop

InlineVariableInExpressionTree — Java

The expression tree of an expression involving a variable inlines the variable's definition

LocalVariablesAutoInitialized — Java

Local variables are automatically initialized

LoopBodyScopeImpliesLoopLifetime — Java

Lifetime of variables declared in a loop body extends across all loop iterations

MultiReferenceVariable — Java

A reference variable can point to multiple objects

MultiValueVariable — Java

A variable can contain more than one value

MustInitializeFieldInConstructor — Java

Constructors must assign values to all fields

NoAtomicExpression — Java

Expressions must consist of more than one piece

NoAtomicExpression — JavaScript

Expressions must consist of more than one piece

NoAtomicExpression — Python

Expressions must consist of more than one piece

NoCastIfSameSize — Java

If a variable is at least as big (bit-width) as a value, then no cast is needed to a assign the value to the variable

NoLocalVariables — Java

There are no local variables

ObjectLabeledWithVariableName — Java

In stack and heap diagrams, an object on the heap is labeled with the name of the variable that refers to it

ReferenceLabeledWithDynamicType — Java

In stack and heap diagrams, reference variables are labeled with the types of the objects they refer to

ReferenceToVariable — Java

References can point to variables

ResetStateEachProgramExecution — Scratch

Running a Scratch program first resets the state of the world and then executes the program

ThisAsField — Java

this is a special field in the object

ThisAssignable — Java

One can assign to this

ThisAssignable — JavaScript

One can assign to this

ThisExistsInStaticMethod — Java

this is a local variable, also in static methods

UndeclaredVariables — Java

Variables don't need to be declared

UntypedVariables — Java

Variable declarations don't need a type

UseOfSelfTypeImpliesRecursiveType — Java

If a class has a method that has a local variable, parameter, or return value with the class as its type, the class is a recursive type

VariablesHoldExpressions — Java

= stores an expression in a variable

VariablesHoldExpressions — Python

= stores an expression: it stores a reference to the expression in a variable

VariablesHoldObjects — Java

A variable of a reference type contains a whole object

VariablesHoldObjects — Python

A variable contains a whole object