Welcome to Introduction to Programming Concepts – Part 1. After watching this video, you will be able to: Describe the purpose and use of identifiers in programming. Describe the purpose and use of containers in programming. To fully understand software programming, there are some fundamental programming concepts you need to know first. The first concepts you will look at are identifiers. Software developers use an identifier to reference a program component such as a stored value, a method, an interface, or a class, by assigning a custom-named label to it. If the identifier stores data, then the data values in the program can be one of two types: either a constant, or a variable. A constant is a data item whose value does not change within a program. This could be a numerical constant such as the mathematical value of Pi, or it could be a text string that remains constant such as a player’s name within a game. Constants are also referred to as ‘named constants.’ You assign a value to a constant when you define it. For example, you might want it to refer to a numerical value within your program such as Pi, or a cost price, or a rate of tax, and then, rather than repeatedly retyping the same numerical value, you can just declare a constant for that value instead, and name it something meaningful like ‘pi_value’, or ‘cost_price’, or ‘tax_rate’. There are a couple of major benefits to using constants in your programs; one is for ease of readability in your code, and the other is that if the specified value changes in the future, you only need to change it once on the constant, rather than finding every instance of that numerical value within your code and changing it. The other type of identifier used in programming is a variable. As the name suggests, this kind of identifier is not constant; its value can change during the program’s execution, such as a user entering their age in an application or a high score in a game. Variables can be strings of text, numerical values, or any other type of data. Using a variable as an identifier is a useful way to refer to program items that are unknown to you, such as a username, a service, or a file name for instance. If you don’t use a variable, then you will need to hard code all the names and values in your program, which is not considered best practice. Variables can be declared and assigned a data type and initial value as they are defined, or you can decide not to assign an initial value when you define a variable, and instead have the value assigned later by instructions within the program. In addition to the identifier data structures already discussed, there are also special kinds of identifiers that can reference multiple elements in a program, and these are referred to as containers. Being able to specify multiple elements means that you don’t have to create a variable for every individual element. This makes it faster and more efficient. For example, if you only want to store six numerical integers, then you could argue that you could just create six variables, one for each. But what if you need to store 1,000 integers or more? In such a case, defining 1,000 variables would obviously be an unwieldly and inefficient programming technique, so in this case you would use a container. There are two types of containers to specify multiple elements: arrays and vectors. The simplest of these container types is an array. In an array, a fixed number of elements of the same type are stored in sequential order, starting from index zero. When you declare an array, you specify the data type of the values it contains, such as an integer, or boolean, or a string, and then the maximum number of elements it can contain. The syntax for declaring an array is to specify the data type first, then the name of the array, then the maximum size of the array in square braces. In contrast to arrays that have a fixed size, vectors have a dynamic size, and they will automatically resize themselves as you add elements to them or remove elements from them. For this reason, you may also see them referred to as dynamic arrays. Because they are dynamic in nature, vectors take up more memory space than arrays, and their elements also take a little longer to access than elements in an array, as they are not stored in sequential memory locations. The syntax for declaring a vector is to specify the container type of the vector first, then specify the data type in angle brackets, then the name of the array. Note that because it is a vector, you do not need to specify a maximum number of values it can contain because the size is not fixed, it is dynamic. In this video, you learned that: Software developers use an identifier to reference a program component. If an identifier stores data, then it can either be a constant or a variable. A constant is a data item whose value does not change within the program. A variable is not constant; it can change during the program’s execution. In an array, a fixed number of elements of the same type are stored in sequential order, starting from zero. And vectors have a dynamic size, and they automatically resize themselves as elements are added or removed.
