第7章高水準プログラミング言語

In 2000, Microsoft announced C# would be its flagship language. It also has the same fundamental syntax as C++ and Java. However, it is purposed to support Windows applications by closely tying in with Microsoft’s net framework, but it can also be used on Linux and macOS. Net C# is a multi-language, component-based software development tool designed to play nicely with all of the .Net languages including C#, Visual Basic.Net, and Managed C++.

HLLs are important in every industry. One example is Python. Part of its purpose is to support data analytics to process complex data, a major focus of many industries today. It does this with built-in analytics tools in its API which can process raw data and produce information and graphics that can be used to make business decisions. For example, a company interested in generating a graphical representation of its products’ sales across various regions during the past year may use Python data analytics and plotting libraries.

Can you elaborate on how useful it will be to know about HLLs in an industry of your choice (e.g., finance, gaming, travel)? Hint: Think about industries which tend to specialize in specific areas.

Logic-based programming languages are those which incorporate a syntax to represent facts and rules about approaches to problems. They have been used to support rule-based approaches as part of the development of artificial intelligence (AI), the simulation of human intelligence by machines such as computers.

The most common language for logic-based programming is Prolog. It is used for both AI and linguistics programming. It is actually an older HLL first developed in 1972 and has stayed with us, receiving extensive updating as AI developed. Figure 7.6 illustrates on the left side how facts and rules can be specified in Prolog. The query window on the right side illustrates how the Prolog fact database can be queried to leverage available rules.

All computer languages can be grouped into particular categories. These are based upon support for certain programming paradigms (standards, perspectives, or sets of ideas that may be used to describe the structure and methodologies of an HLL). These paradigms include imperative/procedural, logical, functional, object-oriented, event-driven (the behavior of programs is controlled by actions (events) which are listened for and then acted upon or handled), and parallel programming (dividing a program into concurrent processes). Our modern HLLs are almost always hybrid combinations of these. We will learn about this in more detail in the following subsections of this chapter.

As we have discussed, imperative HLLs take the “tell the computer what to do” approach. This approach is different from that of declarative HLLs that tell a program to obtain information without prescribing how the program should go about doing it. Declarative languages are used to interact with systems that are programmed to figure out these details. An example of a declarative language is Structured Query Language (SQL), which is used to specify a query that a database system can process to store or retrieve data. Imperative languages typically focus on evaluating expressions and storing results in variables. There are other shared features of these languages, such as iteration (looping or repetition).

Procedural languages extend the imperative paradigm. They make use of procedure calls to change the flow of control. A procedure (function) can be called from anywhere in a program to have it perform a particular job. Some of the languages that support this paradigm are Fortran, COBOL, Pascal, Visual Basic, Ada, C, C++, and C#. Scripting languages, including Python, JavaScript, and PHP, may also be of this type.

Most imperative languages also embrace event-driven programming. This paradigm allows the generation of events (for example, as a user clicks on a button). In general, computer operating systems constantly process events of various types that result from interaction with users or are generated by application programs or computer hardware. In event-driven programming, a program is told to listen for selected events, such as the single-click on a particular object (e.g., a button on a UI). The programmer establishes an event handler to deal with the event whenever it is triggered.