Assembly Languages

Assembly languages are the second-generation programming languages and first to use alphanumeric symbols to write code. The creation of assembly languages depended on the development, using machine language, of an assembler. An assembler is a program that translates the assembly code into machine language. It is necessary to have one assembler for each kind of assembly language and for each kind of computer used.

Assembly languages are the simplest improvement over machine language; their commands are simple mnemonic codes that stand for the binary instructions of machine code. When programmers need to deal with the computer directly, they use assembly language; because it is so close to the hardware level, it is possible to write very efficient programs in assembly language. That same closeness to the hardware level, however is what makes assembly language difficult to use for large programming projects. Therefore, most assembly programming today is used for writing small modules that can be included in larger programs written in more convenient languages.

Procedural Languages

Procedural languages are the third-generation languages. They are also called high-level languages because they represent a higher level of abstraction from machine code than do assembly languages. Procedural languages employ more human-like words, and each has its own set of syntax rules. They are also more efficient, allowing the programmer to express with one statement what would take several commands in machine language. They are called procedural languages because they allow the programmer to create procedures that implement structured programming. Procedural languages are by far the most widely used programming languages.

The development of procedural languages was started by the invention of translation programs that could convert the syntax of the high-level language to machine code that the computer could execute. These translators are compilers and interpreters.

A compiler converts an entire program written in a high-level language to machine language, storing it in what is called executable file, to be run later at the user's discretion. The original code is then called the source code, and the machine-language code is called the object code.

An interpreter reads each high-level program statement, then translates it to machine language and instructs the computer to execute the statement immediately. It creates no object code and no executable file; from the programmer's or user's standpoint, the computer executes the original code. This method of execution gives the programmer more immediate control of the machine and lends itself to an interactive method of programming and refining code and testing it immediately. The interpreter program does not permanently change the code, allowing users or programmers to make additions and other modifications to the program more easily. However, interpreting the code takes more processing than running a compiled program, so interpreted programs generally run slower than compiled programs.

Some of the most frequently used procedural languages include the following: BASIC, PASCAL.

Problem -Oriented Languages

Fourth -generation languages, the problem-oriented languages, are a mixed bag of strategies to make programming easier. They were created to solve specific user and programming problems rather than to achieve the broad general usability of procedural languages. This group of languages includes object-oriented languages, application generators, authoring systems, HyperTalk, and query languages.

Object-Oriented Programming.

Object-oriented programming (OOP) takes a different approach to creating applications. Traditional programming treats data and instructions as separate items with the instructions controlling the data; the instructions are active controls on passive data. In object-oriented programming, an object is created by joining data and instructions in a process known as encapsulation. Once an object is made and debugged, it will work. Objects can then be linked together with messages (calls to the object to implement its instructions on its data) to form full-fledged applications.

Query languages.

Query languages are used specifically within the realm of databases. These languages are designed to instruct the computer to retrieve and manipulate database information and can be used to develop specific applications based on databases, such as database publishing and project management.