of the instructions in a program as a single batch,
and the resulting machine language instructions,
called object code, are placed in a new file. As an
into machine language is more common with Web-
based programs called scripts, written
in
languages such as JavaScript and
Section 4 Software Basics
VBScript. These scripts contain high-level instructions, which arrive as part of a Web page. An interpreter reads the first instruction in a script, converts it into machine language, and then sends it to the microprocessor. After the instruction is executed, the interpreter converts the next instruction, and so on. Programs written for a computer may be in one of the following categories: （ 1 ） Binary code. This is a sequence of instructions and operands in binary that list the
Chapter 5 Computer
Section 4 Software Basics
A support module provides an auxiliary set of instructions that can be used in conjunction with the main software program. Each module is stored in its own file. Unlike a program file, a support module is not designed to be run by the computer user. Instead, these modules are "called" by the computer program, as needed.
Software is categorized as either system software or application software. System software helps you to manage your files, to load and execute programs, and to accept your commands from the mouse and keyboard. The system software programs that manage the computer are collectively known as an
A data module, as you might expect, contains any data that is necessary for a task, but not supplied by the user. For example, word processing software checks spelling by comparing the words in
Section 4 Software Basics
exact representation of instructions as they appear in computer memory. （ 2 ） Octal or hexadecimal code. This is an equivalent translation of the binary code to octal or hexadecimal representation. （3）Symbolic code. The user employs symbols (letters, numbers, or special characters) for the operation part, the address part, and other part of the instruction code. Each symbolic instruction can be translated into one binary coded instruction. This translation is done by a special program called an
Section 4 Software Basics
operating system, and differ from the application programs, such as Microsoft Word, or Netscape, or the programs that you write, which you normally run to get your work done. Windows and UNIX are the best known examples of an operating system. The operating system is an essential part of the computer system. Like the hardware, it is made up of many components. A simplified representation of an operating system is shown in Fig.5-1. the most obvious element is the user interface that can be defined as the combination of hardware and
alternative to a compiler, an interpreter converts one
instruction is running.
This method of converting high-level instructions
Section 4 Software Basics
high-level language into machine language can be
accomplished by two special types of programs:
compilers and interpreters. A compiler translates all
Section 4 Software Basics
a document with the words in a dictionary file of correctly spelled words.
When a computer programmer develops or writes software, he has to select a suitable computer language that provides the tools that he uses to create software. These languages help the programmer produce a lengthy list of instruction, called source code, that defines the software environment in every detail—how it looks, how the user enters commands, and how it manipulates data. Most programmers today prefer to use high-level
A computer's microprocessor only understands machine language in binary form—the instruct set that is "hard wired" within the microprocessor's circuits. Therefore, instructions written in a highlevel language must be translated into machine language in binary form before a computer can use them. The process of translating instructions from a
Section 4 Software Basics
software that helps people and computers communicate with each other. Your computer user interface includes the mouse and keyboard that accept your input and carry out your commands, as well as the display device that provides cues to help you use software, and displays error messages that alert you to problems. An operating system typically provides user interface tools, such as menus and toolbar buttons, which define the "look and feel" for all of its compatible software. Most computers today feature a graphical user interface.