Variables in C++ - Reading Assignment

[JeffE]

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

2. What is the Definition of a variable?
   It is a kind of declaration that is used for a variable.

3. What is Instantiation of a variable?
   It is a piece of memory that is set aside and is within the RAM.

4. What is the difference between an l-value and an r-value?
   I-values have their value placed in the memory, while r-values is not connected to any memory and is a variable without an address.

5. What is an uninitialized variable and what kind of behavior can you expect from such a variable?
   It is a variable whose value has not been stored by a memory address yet. Using these can lead to the variable being undefined.

6. What is undefined behavior?
   It is when code is executed but the variables are not defined well.

[Jamie_Frame]

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

What is the Definition of a variable?
It is a statement of the variable type, name and value.

What is Instantiation of a variable?
This is when the variable is created and given a memory allocation during the runtime.

What is the difference between an l-value and an r-value?
An I-value is any value with an allocated memory location. An r-value is not associated with a specific memory location and will be generally discarded at the end of the statement.

What is an uninitialized variable and what kind of behavior can you expect from such a variable?
An uninitialized variable is one which has not been given a specified value but rather takes the value currently held by the memory slot. This means that each time the program is compiled and run the uninitialized variable may print a different value, until an initial value is assigned to the variable.

What is undefined behavior?
Undefined behaviour refers to a program whose behaviour or output is defined to be unpredictable or unstable.

[LukeM]

1)What is a variable in C++?
An object (a region of storage that contains a value) that is named.

2)What is Definition of a variable?
A declaration statement that determines the variable type as well as identifies it to the compiler.

3)What is Instantiation of a variable?
At runtime, the assignment of the variable to a memory address.

4)What is the difference between an l-value and an r-value?
lvalue refers to a memory location that defines an object. rvalue is a data value stored at some address in memory. In short, they are expressions that function on the left side and right side, respectively, of an assignment expression

5)What is an uninitialized variable and what kind of behaviour can you expect from such a variable?
A unassigned variable that is tied to the garbage value in memory that it points to. Thus it does not have a known value. Using an uninitialized variable will cause unexpected results.

6)What is undefined behaviour?
The result of executing code whose behavior is not well defined by cpp–i.e. there are no rules to determine what will happen.

[chrisDs]

1. A variable in C++ is an named object used to store data

2 It is a type of object in programming that can be used to store data in an allocated memory.

3. Assigning a value for a variable

4. l-values have persistent memory. they are used in the left side of an expression. r-values are temporary and are discarded after the expression is evaluated. They can only be used on the right side of the expression.

5. AN uninitialized variable has an allocated memory but does not have a value explicitly assigned with it. It has an unpredictable behavior since it may store a garbage value.

6. It is a behavior in the program that is not clearly defined in the code.

[Pendar]

1. What is a variable in C++?

An object with a name used to store values

2. What is the Definition of a variable?

A declaration statement to define a variable is called Definition
The data type is stated, followed by the variable name.

3. What is Instantiation of a variable?

When we set aside a some variable RAM to use with our memory

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

I-Value has a modifiable value in memory (persistent to change)
R-Value has a set value in memory

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

Not safe to do. Memories need to be initialized

6. What is undefined behavior?

When we execute a code where its behaviors aren’t well defined by the language.

[Chillie]

1. A named object.

2. Declaration used to make a variable

3. When an object is created and given a memory address.

4. I-values are values that are stored in memory (Glass plates and Silverware). r-values are lost after every statement (Paper plates).

5. Uninitialized variables are variables with no fix location about as unpredictable as you can get.

6.Undefined behavior running programs that cause unpredictable behavior such as Uninitialized variables.

[CryptoRealNews]

1. Variable in C++ is a named region in a particular spot in memory
2. A variable represents a piece of data that it points to. (If the data is changed the variable represents that new data but the variable name remains the same)
3. Creating a variable by definition which also assigns it an address
4. r-value doesn’t have a location or address but as written, it can assign the written value to an l-value (which does have a location or address). Otherwise afterwards the result is discarded.
5. An unnauthorised variable is one that has not yet been specified a value or its value is something random but unknown. Behaviour therefore is an unexpected and unpredictable.
6. Undefined behaviour can be a result of an unitiatiated variable - It will give a result but that result may or may not be correct.

[Caupuri]

1. What is a variable in C++? It’s a named object.

2. What is the definition of a variable? A variable is a named region of memory.

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

4. What is the difference between an l-value and an r-value? An l-value represents an object that occupies some identifiable location in memory (i.e. has an address). Therefore, from the above definition of l-value, an r-value is an expression that does not represent an object occupying some identifiable location in 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 is called uninitialized. The usage of such a variable leads to unpredictable results as its value will be retrieved from the location to which it was allocated.

6. What is undefined behavior? The result of executing code whose behavior is not well defined by the language.

[mayjer]

1. What is a variable in C++?

A named object that contains a value.

2. What is the Definition of a variable?

Something that can store a value. Usually this value can be changed.

3. What is Instantiation of a variable?

The creation of an object. This assigns an object a location in memory. Variables must be instantiated (declared) before they can be used.

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

• L-values are expressions that refer to memory location- like a variable. They can appear the on left side of an assignment
• R-values are expressions that evaluate to a value. They appear on the right side of an assignment
• All L-values are r-values, but not all r-values are L-values

Note: I could not find this info anywhere in the article up to the end of Chapter 1. Fortunately the internet provideth and a search found the MS c++ docs here: https://docs.microsoft.com/en-us/cpp/c-language/l-value-and-r-value-expressions?view=vs-2019

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

• A variable that has not yet received a known value
• If the variable is used before it is initialized the results are unpredictable as it will have whatever random value that memory address happened to contain when it was allocated.

6. What is undefined behavior?

Executing code with indeterminate results. I.e.

• Produces different results each time
• Incorrect results
• Inconsistent results
• Program crashes

[mjwatson10]

1. A named object
2. A reference point for a variable that the compiler notes whenever the variable is called
3. When the object is created and given a memory address
4. l-value is something that points to a specific memory location, r-value is something that doesn’t point anywhere(only use once in it particular statement and cannot be used outside of the statement).
5. A variable that has not been given a known value
6. Execution of code that has yet to be defined in the C++ language

[john_coraline]

1. A variable in c++ is a named object.
   That object is automatically stored in the memory in the computer

2. Definition is when you assign a value to the variable by using the = operator

3. Instantiation is when the object is created and assigned a memory address

4. Uninitalized variable is an object that haven’t been signed a value. It will give
   you random results since the compiler will assign it any unused memory

5. When you’re using values from uninitialized variables and try to execute them in a program.
   It will have randomly different outcomes that might for example result in a crash or
   produce different results every time

6. I-value has a specific location in the memory. R-value uses any free location in the memory

[DDanDonut]

@ivan

• What is a variable in C++?
• What is the Definition of a variable?
• What is Instantiation of a variable?
• What is the difference between an l-value and an r-value?
• What is an uninitialized variable and what kind of behavior can you expect from such a variable?
• What is undefined behavior?

*In C++ a variable is and object that is named

*Variables are a named region of storage that can store a data value.

*It is defining a variable and the type of it

*if either or both of them are defined as a variable, the difference between them is that they are different identifiers

• It doesn’t have memory address and the object doesn’t exist, it can’t be used to store values

*It means an undefined data type.

[ZAR]

@ivan

• What is a variable in C++?
• What is the Definition of a variable?
• What is Instantiation of a variable?
• What is the difference between an l-value and an r-value?
• What is an uninitialized variable and what kind of behavior can you expect from such a variable?
• What is undefined behavior?

1. A variable is an object that takes up space in memory.

2. The value of a stored object in memory.

3. Instantiation means an object will be created and stored in memory (the creation of a variable).

4. L value is the memory location which defines the object, r value is the data value stored at the memory location.

5. It is a variable not given a known value which will trigger undefined behavior.

6. Undefined behavior occurs when uninitialized variables are coded. The code may execute as otherwise intended, however not always the case.

[JustinP]

1. A variable in C++ is a named object. An object is a region of memory storing a value.

2. Defining a variable is giving it a binding. eg. int x; defines a variable named x which is an integer

3. Instantiation of a variable is when the variable is created and it’s object is stored in a memory location.

4. an l value is a value that can appear on the left side of an expression and an r-value can appear on the right.

5. an uninitialised variable has not been assigned a value. Rather than assigning it zero or null by default, the compiler will assign it whatever value was in that memory location which can lead to unexpected results.

6. Undefined behaviour is when an uninitialised variable is being used and therefore is working with unexpected values/data types.

[Toby_K]

@ivan

• What is a variable in C++?
• What is the Definition of a variable?
• What is Instantiation of a variable?
• What is the difference between an l-value and an r-value?
• What is an uninitialized variable and what kind of behavior can you expect from such a variable?
• What is undefined behavior?

1. A region of storage with a value and possibly other properties is called an object. A named object is called a variable in C++.
2. see 1.
3. Instantiation means the object will be created and assigned a memory address at compilation.
4. An I-value has a permanent address in memory, an r-value does not.
5. An uninitialized variable has not been given a value. The compiler will assign a random block of memory to it, which changes every time the code is compiled and run.
6. That is behavior of executed code that is not well defined by C++.

[DreamtGalactic]

1. In C++ a variable is a named object.

2. A variable can be defined as the location in a computers memory where the value of an object is stored. C++ excludes functions from its definition of a variable.

3. Instantiation of a variable is a special kind of declarative statement, which means that an “object will be created and assigned a memory address.”

4. An I-value is a value that is assigned in memory (persistent). An r-value is assigned to a non-persistent address, because that address has not been defined in the code.

5. An uninitialized variable is a variable which has not been assigned a value, meaning it does not have an assigned memory location.

6. Undefined behavior is what happens when an uninitialized variable is compiled and run. C++ does not have rules for when this happens which is why the behavior is undefined.

[iamchaoticcoder]

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

2. What is Definition of a variable?
   a named and specifically typed object to hold a value

3. What is Instantiation of a variable?
   creating a new version of the variable, and setting it to memory

4. What is the difference between an l-value and an r-value?
   I-value is stored in a persistent memory address, but the r-value is not in a persistent location.

5. What is an uninitialized variable and what kind of behaviour can you expect from such a variable?
   when an uninitialized variable may be referenced, but was not instantiated and does not have a value associated can cause unexpected bahariours

6. What is undefined behaviour?
   When a program shows unexpected results as a result of improper code.

[Vidmantas]

1. What is a variable in C++?
   A named object
2. What is the Definition of a variable?
   A memory location for holding value for an object
3. What is Instantiation of a variable?
   The object will be created and assigned a memory address when when program is run.
4. What is the difference between an l-value and an r-value?
   l-value is assigned to an address in memory. an r-value is the opposite, a temporary value.
5. What is an uninitialized variable and what kind of behavior can you expect from such a variable?
   A variable that has assigned memory but no value has been set yet. So the value will be the value of that unassigned memory, which in practice can be any value.
6. What is undefined behavior?
   Behaviour that is not defined by C++. it can crash, show different results each time, or be unpredictable in other ways.

[dAnijboned]

1. What is a variable in C++?
   An element that allows us to hold/store values.

2. What is Definition of a variable?
   The process/statement where we actually write (declare) the variable.

3. What is Instantiation of a variable?
   The process/statement where we assign a value to the variable.

4. What is the difference between an l-value and an r-value?
   An l-value represent (refers to) memory locations. An r-value refers to the actual value stored in memory.

5. What is an uninitialized variable and what kind of behavior can you expect from such a variable?
   A variable that has been declared, but no actual value has been assigned to it. The behavior may be undefined.

6. What is undefined behaviour?
   A situation where we may get unexpected results.

[zzzsoren]

1. What is a variable in C++?
   A named object of a type, and an identifier that is the name of the object.

2. What is the Definition of a variable?
   A statement that provides a type, an identifier, and instantiates the variable.

3. What is Instantiation of a variable?
   The process of creating an object and assigning it to an address in memory.

4. What is the difference between an l-value and an r-value?
   A lvalue expression can have a value assigned to it, while a rvalue expression cannot.

5. What is an uninitialized variable and what kind of behavior can you expect from such a variable?
   A variable that is declared but not set to a definite value before it is used. Therefore, whatever contents of that memory at the time will appear as the initial value of that variable.

6. What is undefined behavior?
   Memory accesses outside of array bounds, memory accesses of uninitialized variables, signed integer overflow, null pointer dereference. etc. Compilers are not required to diagnose undefined behavior, and the compiled program is not required to do anything meaningful.