005.machine languages, assembly languages and high- level languages.

Programmers write instructions in various programming language, some directly under- stand able by the computer and other that require intermediate translation steps. hundreds of computer languages are in use today. These may be divided into three general types:

1.machine language

2 assembly language

3 high- level language

any computer can directly understand only its own machine language. Machine language is the "natural language" of a particular computer. It is defined by the hardware design of that computer. Machine language generally consist of strings of numbers[ultimately reduced to 1st and 0s] that instruct computers to perform their most elementary operations one at a time. Machine language are machine dependent[i.c,a particular machine language can be used on only one type of computer]. Machine language are cumbersome for humans, as can be seen by the filling section of a machine language  programs that adds overtime pay to base pay and stores the results in gross pay.

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As became computers more popular, it became apparent that machine- language programming was simply too slow and tedious for most programmers. Instead of using the strings of numbers that computers could directly understand, programmers began using English- like abbreviations to represent the elementary operations of the computer. These English- like abbreviations formed the basis of assembly languages. Translator programs called assemblers were developed to convert assembly language programs to machine language at computer speeds. The following section of an assembly- language program also adds overtime pay to base pay and stores the resylt in gross pay, but more clearly than its machine- language equivalent.

Load basepay

Add overpay

Store grosspay

Although such code is clearer to humans, it is incomprehensible to computers until translated to machine language.

Computer usage increased rapidly with the advent of assembly language, but programming in this still required many instructions to accomplish even the simplest tasks. To speed the programming proces, high- level languages were developed in which single statements could be written to accomplish substantial tasks. The translator programs that convert high- level language program into machine language are called compilers. High- level language allow programmers to write instructions that look almost like everyday English and contain commonly used mathematical notation. A paroll program written a high- level language might contain a statement such as;

obviously, high- level language are much  more desirable from the programmer's standpoint than either machine language or assembly language. C, C++ and java are among the most powerful and most widely used high- level programming language. The process of compilling a high- level language program into machine language take  a considerable amount of computer time. Interpreter programs were developed to directly execute high- level language programs without the need for compiling those programs into machine language. Although compiled programs execute much faster than interpreted programs, interpreters are popular in program development invironments in which programs are recomplied frequently as new features are added errors are corrected. Once a program is developed , a compiled version can be produced to run most efficiently.As we study java, you will so that interpreters have played an especiacally important part in helping java achive its goal of portability across a great vareity of platforms.