A reserved word is a word or symbol that has a special meaning, specific to or part of a particular programming language or a specific program. Reserved or restricted keywords are used to control how that program is defined. Programs are simply a set of instructions for manipulating data within the computer environment. These instructions are written in a particular programming language. There are many different programming languages. Java, C, C++, BASIC, COBOL, and Pascal are just a few of the high-level languages used by programmers. Some examples of reserved words in the Java programming language are "break," "while," "catch," and "try."
Instead of the term GOTO, Java uses the term "break." The goto term in other programming languages is a way to arbitrarily branch, i.e., a way to control flow. The term break refers to the process of breaking out of a block of code. Code is a colloquial term for written computer instructions and can appear in a variety of different forms. To illustrate, the code that a programmer writes is called source code. However, computers can only execute instructions that have been written in machine language. To get from a high level language that programmers use to one that the computer can understand it must first be transformed by a compiler. The compiler reorganizes the source code. Once it has been compiled, it is called object code. Executable code is code that is ready to run. When a user buys software, he is buying an executable version of that program. In the Java language, break is also used to break out of LOOPS and SWITCH statements.
"While" is Java's most basic and powerful looping statement. Simply put, looping executes a single statement over and over again until a certain condition has been met; for example, until a Boolean (true or false) statement continues to be true. Each pass through a loop is called an iteration. A SWITCH is just another word for an option or a parameter, i.e., something added to a command to somehow change or refine that instruction. Options, as the term implies, are not required. For example, within the DOS operating system, an option has a slash (/) in front of it. If you ask the computer to display it's directories with the DIR command, the /P option instructs the computer to pause between screens. Every application or operating system has different rules for identifying options.
"Catch" and "try" are two reserved words that handle exceptions in the Java programming language. An exception is any unusual or abnormal condition encountered during the running of a code sequence. Previously, other programming languages forced programmers to use return codes, but these are subject to many failures. This is because it is often necessary to understand, at many levels, the intimate details of possible error conditions. The try keyword can be used to specify a block of code that should be guarded against all exceptions. Immediately following a try statement, a catch clause is inserted, which specifies the exception type the user desires to catch.
Words and symbols that are reserved within each program have specific meanings to that program's compiler.
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