Undefined is a type returned in Javascript. In c++ the program may run fine or crash unexpectedly seemingly on random places. 
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This isnât related to the question but whenever I try to run code in codeblocks, I keep getting this error - Execution of âdoxygenâ failed.
Please ensure that the doxygen âbinâ directory is in your path or provide the specific path in DoxyBlocksâ preference.
And I looked it up and Iâm still really confused as to what this is. Do I have to download packages that have this?
What OS are you using? I havenât seen this error before. I found this post that suggests disabling the plugin, hope it helps:
http://forums.codeblocks.org/index.php?topic=19188.0
Iâm using windows, and codeblocks was not my favorite to code with so Iâm using visual studio now.
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Excellent! You can use any text editor or IDE you want, happy you made it work 
I donât use codeblocks either 
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- a variable is a named object
- the definition of a variable is the statement used to declare it
- instantiation is when an object is assigned a memory address
- an r-value is a variable without an address, it can be used to assign a value to an l-value. an l-value has its own memory address
- an uninitialized variable is one that has not been given a value, whether by initialization or assignment. The computer may go to fetch or use memory that has no assigned value, and instead return something inexplicable.
- undefined behavior, often called UB, results when you execute code with ill-defined language, producing unexpected results.
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A variable in C++ is a named object or item of data. Most objects created in C++ are variables.
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A variable is an object or data item with a region of storage that may take on more than one value during the runtime of a program.
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Instantiation of a variable is when an object is created and assigned a memory address. Once instantiated, a variable is able to store a value.
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An L-value represents an object that occupies some identifiable location in memory while an R-value is defined by exclusion and is only considered as an expression because it does not represent an object occupying some identifiable location in memory.
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An uninitialized variable is a variable in memory that has not been given a known value through initialization or assignment. Almost anything can happen with an uninitialized variable which is why it is good practice to assign a value after the variable is created or initialize a value upon creation of the variable.
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Undefined behavior is the result of executing code whose behavior is not well defined by the C++ language.
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- It is a pointer to a piece of information stored in RAM that program will use
- A named object
- It is when a variable receives the address to its part of RAM that it will occupy.
4.An I-Value has a location in memory while an R-value doesnât necessarily take up memory or point to a specific location. - It is a variable without a value assigned to it and we expect undefined behavior.
- When an uninitialized variable is called in a program it points to the location that the compiler assigned to it. Whatever data is in that location will be return to the program, an old file, previous program data, etcâŚ
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What is a variable in C++?
A variable in C++ is an object that stores values. -
What is the Definition of a variable?
The definition of a variable depends on the type of value (eg int for integers, string for strings and bool for booleans. -
What is Instantiation of a variable?
Instantiation defines where the location that the variable information will be stored in memory. -
What is the difference between an l-value and an r-value?
An l-value has a specific memory location. Variables are something that have l-values. R-values are values that donât have a specific location that they are stored. -
What is an uninitialized variable and what kind of behavior can you expect from such a variable?
An uninitialized variable is one that has been declared hasnât been assigned a value yet. In this case the value it will output when called is whatever value was previously stored at the memory location the new variable is saved. -
What is undefined behavior?
Undefined behavior occurs when the code being run isnât well defined. This can occur when there is an uninitialized variable. Undefined behavior can still compile and run but the results are unpredictable.
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1. What is a variable in C++?
A named region in memory.
2. What is the Definition of a variable?
A special kand of declaration statement.
3. What is Instantiation of a variable?
When an object is created and assigned a memory address.
4. What is the difference between an l-value and an r-value?
L-value is the name of the variable, and an address in memory. R-value is the actual value stored in the variable and memory.
5. What is an uninitialized variable and what kind of behavior can you expect from such a variable?
A variable that has not been given a value, it will produce whatever value may be in its memory location.
6. What is undefined behavior?
An unpredictable behavior that might occur if variables are uninitialized
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- A variable is a named region of memory.
- Variable is used to store data in a memory location.
- Instantiation means the object will be created and assigned a memory address.
- left of assignment operator is l-value and right of assignment operator is r-value.
- A variable that has not been given a known value (usually through initialization or assignment) is called an uninitialized variable.
Reading the value of an uninitialized variable leads to undefined behavior. - Undefined behavior is the result of executing code whose behavior is not well defined by the C++ language.
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In C++ a variable is a named object
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a region of storage that has a value or certain other attributes
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Variable Instantiation is when you are giving a special kind of declaration statement used to create a variable.
e.g. int x; // define a variable named x, of type int
where âdefine a variable named x, of type intâ is the variable instantiation.
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l-value is the assignee, r-value is a value without an address but is when written it can only be used in order to assign value to an I-value.
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An uninitialized variable is a variable that is declared nut not instantiated. The behavior of this kind of variable is unpredictable
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Undefined behavior is the result of executing code whose behavior is not well defined by the language.
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1. What is a variable in C++?
A named object
2. What is the Definition of a variable?
A declaration statement, where defined variable has a particular type.
3. What is Instantiation of a variable?
The creation and assignment address made for the varible.
4. What is the difference between an l-value and an r-value?
Left and rightâŚpersistent address and not persistent address in memory.
5. What is an uninitialized variable and what kind of behavior can you expect from such a variable?
No attached value⌠Resulting undefined and unexpected behaviour.
6. What is undefined behavior?
Not clear defined code been executed somehow.
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What is a variable in C++?
names object
2 What is Definition of a variable?
In order to create a variable, we use a special kind of declaration statement, ie, int x;
3 What is Instantiation of a variable?
Instantiation , the object will be created and assigned a memory address. Variables must be instantiated before they can be used to store values.
4 What is the difference between an l-value and an r-value?
l-value has-persistent address & r-value is not associated with a persistent memory address.
5 What is an uninitialized variable and what kind of behaviour can you expect from such a variable?
a variable that has not been initialised can lead to undefined behaviour
6 What is undefined behaviour?
result of executing code whose behaviour is not well defined by the language
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What is a variable in C++?
A variable is a named object. An object is a region of storage (usually memory) that has a value and other associated properties. -
What is Definition of a variable?
At compile time, when the compiler sees a definition statement, it makes a note to itself that we are defining a variable, giving it the name x , and that it is of type. From that point forward, whenever the compiler sees the identifier x , it will know that weâre referencing this variable. -
What is Instantiation of a variable?
It means the object will be created, when the program is run, and assigned a memory address. Variables must be instantiated before they can be used to store values. -
What is the difference between an l-value and an r-value?
l-value has-persistent address & r-value is not associated with a persistent memory address. -
What is an uninitialized variable and what kind of behaviour can you expect from such a variable?
An uninitialized variable is in memory, but she doesnât have value assigned to it. Using such a variable can cause unexpected behavior. -
What is undefined behaviour?
Undefined behavior is when the result of the program may exhibit unexpected results. He can work well the three first executions and not at the fourth for example.
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What is a variable in C++?
A variable is a named object in the memory. -
What is the Definition of a variable?
Itâs a basic unit of storage in a program, a name given to a location in the memory. -
What is Instantiation of a variable?
Itâs a creation of the object and assigning its address in memory. -
What is the difference between an l-value and an r-value?
Ivalue represents an object with an identifying address in memory.
Rvalue is an expression that does not represent an object occupying some identifiable location in memory. Rvalue is defined by exclusion. -
What is an uninitialized variable and what kind of behavior can you expect from such a variable?
An uninitialized variable is a variable without a given value, its behaviour will be undefined. -
What is undefined behaviour?
Behaviour without a defined result. Using undefined variable will result in breaking the code.
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What is a variable in C++?
In C++ a vaiable is a named object, in which an object is a region of strage that has a value or other properties.
What is Definition of a variable?
Definition of a variable is the declaration statement that defines name, type.
What is Instantiation of a variable?
The instantiation is the assignement to a certain memory space for a variable during runtime.
What is the difference between an l-value and an r-value?
âl-valueâ refers to memory location which identifies an object.
"r-valueâ refers to data value that is stored at some address in memory.
What is an uninitialized variable and what kind of behaviour can you expect from such a variable?
A variable that has not been given a known value is called an uninitialized variable. Using the value stored in an uninitialized variable will result in undefined behavior.
What is undefined behaviour?
Undefined behavior is the result of executing code whose behavior is not well defined by the language.
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1 - A variable is a named object. The name of the object is called the identifier.
2 - Variables can be defined using declaration statements.
3 - Variables must instantiated before they can be used. Instantiation means the variable will first be created then assigned a memory address in the computers RAM, from here the computer will access the values binded to the variable.
4 - An l-value is a variable that occupies space in the memory of the computer, whereas r-values are not assigned an address in the memory.
5 - A variable that has not been assigned a value is called an uninitialized variable.
6 - When code is executed but the behaviour is not defined by C++, this is known as undefined behaviour. An example is the use of uninitialized variables.
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- An object that is named
- The initialization or declaration of a variable
- When an object is created and assigned a location in memory
- The l-value refers to the object on the left and the r-value refers to the object on the right
- A variable that has not value set, the variable cannot be used in computations
- When the program runs into unexpected exceptions or errors that stop the runtime of the compiler
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Undefined behavior is usually not detected by the compiler (or it depends on the compiler itself). The code will compile fine but might cause issues in runtime.
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