Variables in C++ - Reading Assignment

C++ Programming
#182
  1. In C++, a variable is a named region of memory
  2. Definition of a variable is a special kind of declaration statement used to create a variable.
  3. Instantiation of a variable happens when the object is created and assigned a memory address in the RAM.
  4. An lvalue points to a specific memory location. On the other hand, an rvalue doesn’t point anywhere; generally, it is temporary and short lived. We can say that lvalues are containers and rvalues are things contained in the containers.
  5. An uninitialized variable has not been given a value by the program (generally through initialization or assignment). It will result in undefined behaviour, which is not a good idea. A variable has to be initialized with a value before we can use it.
  6. Undefined behavior (UB) is the result of executing a program whose behavior is not well defined by the language and thus, unpredictable.
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#183

What is a variable in C++?
A named object
What is Definition of a variable?
A memory location for holding a value for an object.
What is Instantiation of a variable?
It means that the object will be created and assigned a memory address.
What is the difference between an l-value and an r-value?
l-values are values that have their place in memory, r-values are values (or expressions) that are discarded at the end of a statement and therefore need not to be associated with a memory address
What is an uninitialized variable and what kind of behaviour can you expect from such a variable?
a declared variable whose value in the memory address has not yet been initialized. using such variables can lead to undefined behaviour
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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#184

Answers

  1. Variables in C++ are named objects (regions of storage), and the name of this object is called identifier.

  2. When you create a variable, you use a special kind of declaration statement called definition. For instance, int x; defines a variable x of type integer.

  3. Instantiation of a variable means, when the program is run, the object will be created and assigned a memory address. All variables must be instantiated before they can be used to store values.

  4. L-value is a variable with a defined region of storage, with it’s own address. R-value is a temporary value that doesn’t persist in memory.

  5. Uninitialized variables don’t have any assigned value. They take a default value, with unpredictable behavior.

  6. Undefined behavior is what we should avoid, the result of executing code that will not defined by C++ language.

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#185

  1. A variable is a named object.

  2. The application of a declaration statement defines a variable.

  3. The object is created and assigned a memory address.

  4. l-values have persistent memory addresses, whereas r-values have temporary allocations.

  5. An uninitialized variable has been defined but has no known value.

  6. Undefined behavior is the result of running an uninitialized variable, which is unpredictable by nature.

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#186
  1. A variable is a named region of memory.
  2. A definition is a declaration statement that we use to create a variable.
  3. If we create a variable, then when a program is run, the variable will be instantiated. Instantiation is a fancy word that means the object will be created and assigned a memory address. Variables must be instantiated before they can be used to store values.
  4. l-value is something that points to a specific memory location. On the other hand, a r-value is something that doesn’t point anywhere. In general, r-values are temporary and short lived, while l-values live a longer life since they exist as variables.
  5. A variable that has not been given a known value (usually through initialization or assignment) is called an uninitialized variable. C++ does not initialize most variables to a given value (such as zero) automatically. Thus when a variable is assigned a memory location by the compiler, the default value of that variable is whatever (garbage) value happens to already be in that memory location.
  6. Undefined behavior is the result of executing code whose behavior is not well defined by the C++ language. In this case, the C++ language doesn’t have any rules determining what happens if you use the value of a variable that has not been given a known value. Consequently, if you actually do this, undefined behavior will result.
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#187

  1. What is a variable in C++?
    A variable is a named object, which is a region of storage in memory that has value and properties.

  2. What is Definition of a variable?
    A variable is a named object, which is a region of storage in memory that has value and properties.

  3. What is Instantiation of a variable?
    The creation and storage of that variable.

  4. What is the difference between an l-value and an r-value?
    i-values have assigned memory addresses, r-values are temporary

  5. What is an uninitialized variable and what kind of behaviour can you expect from such a variable?
    An unitialized var is a defined var but has no value assigned.

  6. What is undefined behaviour?
    The result of running statements with unitialized vars

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#188

  1. An object is a region of storage (usually memory) that has a value and other associated properties. A named object is called a variable.

  2. Special kind of declaration statement is called definition of a variable

  3. . Instantiation means the object will be created and assigned a memory address. Variables must be instantiated before they can be used to store values. Variable will be instantiated in the program runtime

  4. l-value is something that points to a specific memory location. On the other hand, a r-value is something that doesn’t point anywhere. In general, r-values are temporary and short lived, while l-values live a longer life since they exist as variables.

  5. A variable that has not been given a known value (usually through initialization or assignment) is called an uninitialized variable. C++ does not initialize most variables to a given value (such as zero) automatically. Thus when a variable is assigned a memory location by the compiler, the default value of that variable is whatever value happens to be already there in that memory location.

  6. Undefined behavior is the result of executing code whose behavior is not well defined by the C++ language. In this case, the C++ language doesn’t have any rules determining what happens if you use the value of a variable that has not been given a known value. Consequently, if you actually do this, undefined behavior will result.

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#189
  1. Variable is a named object.
  2. Definition of a variable is a special kind of statement.
  3. Instantiation means that the object will be created and assigned to the memory adress.
  4. An l-value ( locator value ) represents an object that occupies some identifiable location in
    memory(has an adress);
    R-value is an expression that does not represent an object occupying some identifiable location in
    memory.
  5. A variable that has not been given a known value is called an uninitialized variable . Using the values of uninitialized variables leads to undefined behaviour.
  6. Undefined behaviour means that the uninitialized variable will take the value residing in some unused memory and we don’t know what will show up.
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#190
  1. Variable is a named object, called an identifier.
  2. A named region of memory.
  3. Instantiation of a variable creates an object and assigns a memory address.
  4. l-value is a locator value, r-value is a data value that cannot be assigned a value.
  5. Uninitialized variables have not been given a value, they are an empty variable in memory.
  6. Undefined behavior = Buggy software, works sometimes.
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#191
  1. Object that has a name.
  2. A statement that declares a name that is defined and stored in a memory.
  3. Object that is created is also assigned in memory.
  4. I-value => has persistent address in memory while r-value => does not.
    E.g. int w; vs int 10;
  5. Variable that has not been assigned to a memory.
  6. Programme cannot run as such functionality does not exist.
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#192

  1. What is a variable in C++? - a named object .

  2. What is Definition of a variable? - a named region of memory.

  3. What is Instantiation of a variable? - this means the variable will be created and assigned a memory address.

  4. What is the difference between an l-value and an r-value? - an i-value has a persistent address (stored in memory) and an r-value is not associated with a persistent address (temporary and discarded after expression is evaluated).

  5. 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 value. The behavior one can expect undefined and unexpected behavior of the program

  6. What is undefined behaviour? - executing code whose behavior is not well defined by the language.

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#193
  1. A named Object in C++.
  2. A variable is a named region of memory.
  3. It means the variable will be created and assigned a memory address.
  4. l-value is anything whose address is accessible. It means we can take the address of l-value using & operator. R-value is anything that is not l-value. It means we cannot take the address of r-value and it also doesn’t persist beyond the single expression.
  5. An uninitialized variable is a variable that has not been given a value by the program. Using the value stored in an uninitialized variable will result in undefined behavior.
  6. Undefined behavior is the result of executing code whose behavior is not well defined by the language.
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#194

What is a variable in C++?
A named object is called a variable

What is Definition of a variable?
Here’s an example of defining a variable named x:

int x;

What is Instantiation of a variable?
Instantiation is a fancy word that means the object will be created and assigned a memory address.

What is the difference between an l-value and an r-value?
An l-value is persistently defined in memory. An r-value is not defined persistently and may be considered the variation of the l-value variable.

behaviour can you expect from such a variable?
An uninitialized variable is a variable that has not ben assigned a memory by the compiler,

What is undefined behaviour?
The result of executing code not well defined by the language

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#195
  1. A variable is a named object representing a memory address.
  2. To define a variable, 2 things are required: a name and a type. Thus, the definition of a variable is writing the statement specifying the type and name of the variable.
  3. It is the creation of its object and the allocation of its memory address.
  4. l-value: memory address of a variable. r-value: the stored value of a variable.
  5. It is a variable with a type and a name, but without a value.
  6. It’s an unpredictable behaviour of the program that can be caused by the use of a variable without a value.
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#196
  1. What is a variable in C++?

A variable is a named region in computer memory.

  1. What is Definition of a variable?

To create a variable, we use a special kind of declaration statement called a definition, e.g. int x creates the integer x.

  1. What is Instantiation of a variable?

Instantiation means the object will be created and assigned a memory address in RAM.

  1. What is the difference between an l-value and an r-value?

l-value has a persistent memory address. An r-value is not associated with a persistent memory address.

  1. What is an uninitialized variable and what kind of behaviour can you expect from such a variable?

An uninitialized variable is a variable that has not been assigned a memory location by the compiler. C++ doesn’t assign most variables automatically. Therefore, when a variable is assigned a memory location by the compiler, the default value of that variable is whatever (garbage) value happens to already be there in that memory location. The behaviour is therefore unpredictable.

  1. What is undefined behaviour?

Unidentified behaviour is the result of attempting to compile code that is not well defined in the language.

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#197

1
In C++ we refer to any chunk of data a computer have to process as an object. When the computer execute the code, it will assign a memory portion to the object. When we give a name to an object we define a variable, from that moment the system will know the memory portion the variable is located.

2
An object with a name (identifier) with defined type too.

3
The instantation of a variable is the assignment of a memory address to the variable at the moment of it’s first identification. This definition is required to correctly store the values of the variable at a certain memory address.

4 not on the linked article. Found in https://www.learncpp.com/cpp-tutorial/611-references/
l-value has a persistent memory address. An r-value is not associated with a persistent memory address.

5 Found in the next section of the article: https://www.learncpp.com/cpp-tutorial/uninitialized-variables-and-undefined-behavior/
It’s a variable only defined in the statement without assigning a value

6
It’s an unpredictable behaviour of the compiler that can be caused by the use of an uninitialized variable.

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#198

Answer:

  1. A variable in C++ is named region of memory by which it can be found.
  2. Variable is a container with the name for a piece of data.
  3. Instantiation of a variable is a process of assigning an address to that variable.
  4. L-value has a memory assign to it. All l-values can be r-values. Not all r-values can be l-values. R-values are all values that cannot be l-values.
  5. A variable that has not been given value is called an uninitialized variable. If you call for an uninitialized variable and print it out, you will never know what is stored in that memory location before you assigned variable to it. So each time, it can give the same or different value. In my case, it was “16”.
  6. Undefined behavior is a process of executing a code whos results won’t be consistent each time it is executed. It can give correct results sometimes, or different results each time, or crash, etc.
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#199

  1. A variable in C++ is a named object.

  2. The definition of a variable is a declaration statement that has a name and a type.

  3. Instantiation of a variable means that the object (variable) will be created and assigned a memory address.

  4. I-value is the memory address of a variable and r-value is the stored value of a variable.

  5. An uninitialized variable is a variable that has not been given a known value and the behavior I can expect is completely random, it will print out whatever value happens to be in the memory location it was assigned to.

  6. Undefined behavior is the result of executing code whose behavior is not well defined by the C++ language.

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#200
  1. It is a named object.
  2. It is the process of creating a variable by specifying its name and type.
  3. It is the process of creating the variable and assigning it to a memory space, in order to have it stored within the program.
    4.An l-value represents an object which occupies a specific, identifiable memory location, whereas an r-value represents an object which does not.
  4. It is a variable that has been declared but which content is not defined. It will likely be a cause for bugs and other errors.
  5. Undefined behavior depends on the fact that a program which has not been coded in a deterministic way has been executed, determining results which are not predictable.
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#201

  1. A variable in C++ is a named object. The identifier of this object is the name. The variable (= the named object) itself uses a place of storage (mostly memory). This variable has, because it is an object, a value and (mostly) further associated properties.

  2. Through a definition of a variable you “create” this variable (giving address and space to it) and give it a name and a data type (e. g. string/ int). With using the name of the variable we can referencing to this variable and use it at a later time.

  3. When you run the program the defined variables get instantiated. That means the object is “generated” and it gets a specific memory address. Before variable can be used they have to be instantiated, otherwise there is no specific address/storage for your object which you want to manipulate.

  4. An l-value is an expression that refers to an object which is (as we have learned before) a region of storage (mostly memory). For beginners the easiest way to understand what a l-value is is the following: An object which is on the left side of an assignment (e. g. int x = 5) is called l-value. In this example x is this l-value. But I read that is not accurate enough, because there are also const objects which cannot appear on the left side of an assignment. An r-value is just the opposide (“right side of the assignment”), that means r-values can only appear on the right side of an assignment.

  5. An uninitialized variable is a named object which is defined (give it a name and a data type but no value e. g. int y) but there is no value assigned to it. That means the right side of an expression is missing (the r-value). When you use such a variable it leads to unexpected results (also called undefined behaviour) because it always uses free memory which can be different any time you run the program.

  6. As already described in 5 undefined behaviour happens when the results of your code is not as desired because the way you written your code is not compatible with the language C++. There are lots of different undefined behaviours. In short, you never know what your program is going to output.

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