• C++ Declaring Variables

'Scope' is a concept which can be applied to many things in C++, and generally refers to the region of code in which something is accessible.

In the case of variables, variables are only accessible after they've been declared in the code. Variables which are defined in 'blocks', which generally means they're in some sort of structure, between curly brackets, are said to have the local scope as these are only accessible by things inside the block in which the variable was declared. Take for example the following in which the variable 'x' can only be accessed from the main function:

There are some rules that must be in your knowledge to work with C variables. Rules of Declaring variables in C. Autotune evo vst free download. A variable name can consist of Capital letters A-Z, lowercase letters a-z, digits 0-9, and the underscore character. The first character must be a letter or underscore. Blank spaces cannot be used in variable names.

So far, we've learnt about many 'blocks', and as alluded to earlier, these can be classified generally by sections of code with curly brackets surrounding them - for example functions, while loops, for loops, if-statements, etc. Nested blocks (blocks inside blocks) also have access to the local variables of their parent blocks, take for example the following:

Note that for cases like the above where only one line should be treated as a 'block' for a statement, we can simply indent the single line and leave out the curly brackets - take, for example, the following:

In C++, we can actually create blocks without any special keywords like 'for' or 'if' just for general purpose by surrounding a section of code in curly brackets. Usually this isn't extremely useful, however in some cases it can provide a good way to isolate 'more local' variables:

On running the above example you can see that local variables (with the same name) are chosen over those of a wider scope. In the example the local variable is hiding the variable in the wider, 'main', scope, and as such there is no easy way of accessing the 'x' in 'main' from the block. This is why naming in this fashion should be avoided if possible.

1. Variables that are declared inside a function or block are local variables. They can be used only by statements that are inside that function or block of code. Local variables are not known to functions outside their own. Following is the example using local variables −.
2. A variable provides us with named storage that our programs can manipulate. Each variable in C has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.
3. Declaration of variables In order to use a variable in C, we must first declare it specifying which data type we want it to be. The syntax to declare a new variable is to write the specifier of the desired data type (like int, bool, float.) followed by a valid variable identifier.

If a variable (or anything else for that matter) is declared outside of any blocks, it is accessible from anywhere in the code. Variables declared this way are said to have global scope, however as convenient as these may be, they are often considered very bad practice. Take for example the following situation:

Once again the local variable takes preference over the global, and hence 5 is outputted. In this case, we could actually use the scope resolution operator (::) to target the variable using the global scope by simply not specifying anything on the left side of the operator:

Generally it's considered bad practice to give multiple variables the same name in situations where it's possible that scope could cause naming conflicts, and in cases like classes, some people like to use different notations to represent member variables to avoid naming conflicts. A popular naming convention is 'Hungarian Notation' which prefixes class member variables with 'm_', for example:

In the case of scope naming conflicts with classes, there is also a hidden pointer passed behind the scenes to every class member function (or at least those that aren't static, but we haven't learnt about that yet!). Take, for example, the above code snippet without the naming conventions:

It's clear what the programmer wants to do here, they want to set the member variables to the local scope parameters. The problem is that the 'age' and 'name' they're setting, are actually the parameters themselves! So if we added an 'output' member function and called this after constructing with the two parameters, we would see that the member variables still hold 'no value':

The best way to solve this would be to change the parameter/variable names. There is, however, another way we can accomplish this by using this hidden pointer. The hidden pointer is named this, and points to the object that the member function is being performed on. As such, we can dereference the pointer and use the dot operator to get the member variable of the object instead of the local member function one. As we covered previously, the (*a).b syntax is identical to the a->b syntax, and as such using the 'arrow' operator makes a lot of sense here. Although it's a bit messy, we could use the following:

There are actually an awful lot of nice things that you can do with access to this hidden pointer. A nice idea is making 'chain-able' member functions. So if related functions of a class return a reference to the object itself (the dereference of the 'this' pointer), then member functions could be chained up in a object.A().B().C() syntax! Note that if we don't set the return type of the function to a reference to the object type, a copy of the object will be passed each time, and so the chaining will completely break.

Chaining member functions is pretty neat, although in this case there is a much cooler solution available if we overload some operators - but we haven't learnt about that yet.

Variables are an extremely core concept to most object orientated programming languages. I like to visualize a variable much like a box. We can put things in the box, we can take things out of the box, and at any point we can see what is inside the box. Each box also has a name to which we can refer to it by, and in C++, each box can only hold a certain type of data.

Miroslav philharmonik 2 vst free download. When we create variables we call this the variable declaration, and then when we set them for the first time, we call this the initialization. To declare a variable in C++, we write the function. To declare a basic integer variable called 'age', we could write the following:

From this point we can then refer to the variable by its name, so in this case, we can just write 'age' whenever we want to refer to the variable. To initialise the variable we can write its name, followed by the equals sign, followed by the value we want to set the variable to (followed by a semicolon). The value we set it to can be a constant (a value that doesn't change), or another variable of the same type. An operator is a symbol which has a certain meaning in the programming language, in this case, the equals operator, represented by the = symbol, is an operator which sets whatever is on the left of the operator to whatever is on the right.

The constant value we set the variable to depends on the to 5 with something like the following:

We can actually combine the variable declaration and initialization into one more-compact line, like the following:

The 'age' variable now contains the number '5', and we can refer to this '5' by writing 'age' anywhere in our program. We can also change the value of the variable at any point by using the equals operator as we did for the first initialization:

Although this seems purely for convenience at the moment (as we could just write '5', '3', or '21' in place of 'age'), trust me when I say that these become extremely useful and powerful when you start dealing with dynamic logic and user input (the latter of which we'll be covering later in this tutorial).

Just to give an example of accessing the contents of variables by using their names, we could create a new variable called 'age_two' which is set to the value of 'age', and then we can also try outputting one or both of these variables:

To be clear, all this code should be going into the basic program structure which we learnt how to create in the last tutorial. So we want our 'iostream' include for cout, cin, and some other stuff, we want the std namespace, and we want the majority of our code to be going in our 'main' function. So our full code to demonstrate variables so far, which you can compile and run at any point to test the functionality, is as follows:

Some number variables can handle positive and negative numbers, whereas 'unsigned' number variables can only handle positive numbers, although because of this restriction, can hold larger numbers. You can write the signed or unsigned keywords before the and 'short' - numbers with a decimal place in. Floats are accurate to around 6 or 7 digits and are declared using the float type. Float constants can be defined by simply writing a number with a decimal point followed by the 'f' notation. An example of a simple float declaration and initialization to a float constant is as follows:

Care must be taken, however, with float (and other decimal) operations, as rounding and precision problems to do with how the numbers are stored can trip you up (we don't have infinite memory for recurring decimals like 1/3 for example) -- I recommend reading this article for more information on this if you're interested.

Doubles

The 'double' or 'e'. Character variables are declared by using the char type, and character constants are defined by using single quotes (apostrophes) around the character. An example of character declaration and initialization to a character constant is as follows:

Strings

C++ Declaring Variables

The lastve talked about string variables in relation to cout before, and as such you should know that string constants are defined by using double quotes. String variables are declared by using the string type, however as strings aren't actually 'primitive' types in C++ (and are instead defined by the standard library of stuff that comes bundled with C++), you are required to #include <string> to use thist strings aren't massively useful, but this is just because we don't really know how to utilize all the functionality of different data-types yet - for example, we don't know how to perform simple mathematics on number types, or how to check the value of booleans to change the logic of the program. All will be revealed in future tutorials.