1.2 Computer systems  (Page 8/8)

This representation is usually defined by the hardware manufacturer, and is based on abbreviations (called mnemonics) that help the programmer remember individual instructions, registers, etc. An assembly language is thus specific to a certain physical or virtual computer architecture

A utility program called an assembler, is used to translate assembly language statements into the target computer's machine code.

Although assembly is more friendly than machine code, use of assembly offer several disadvantages, for instance, each type of computer has its own assembly language or programming assembly requires much time and effort.

Hence, assembly language is not use to write large programs. However, there are some computer application, such as in writing program that control peripherals, assembly is still a necessity.

High-level languages

A high-level programming language is a programming language that, may be more abstract, easier to use, or more portable across platforms.

Examples: Pascal, C, Visual Basic, SQL, . . . .

Such languages often abstract away CPU operations such as memory access models and management of scope.These languages have been implemented by translating to machine languages.

There are two types of translators

• Compiler is a program that translate source code from a high-level programming language to a lower level language (e.g., assembly language or machine language)

• Interpreter is a program that translates and executes source language statements one line at a time.

[link] below shows the process of solving problem with computers

Domain Analysis

Often the first step in attempting to design a new piece of software, whether it be an addition to an existing software, a new application, a new subsystem or a whole new system, is, what is generally referred to as "Domain Analysis". The more knowledgeable they are about the domain already, the less the work required. Another objective of this work is to make the analysts who will later try to elicit and gather the requirements from the area experts or professionals, speak with them in the domain's own terminology and to better understand what is being said by these people. Otherwise they will not be taken seriously. So, this phase is an important prelude to extracting and gathering the requirements.

Software Elements Analysis

The most important task in creating a software product is extracting the requirements. Customers typically know what they want, but not what software should do, while incomplete, ambiguous or contradictory requirements are recognized by skilled and experienced software engineers. Frequently demonstrating live code may help reduce the risk that the requirements are incorrect.

Specification

Specification is the task of precisely describing the software to be written, possibly in a rigorous way. In practice, most successful specifications are written to understand and fine-tune applications that were already well-developed, although safety-critical software systems are often carefully specified prior to application development. Specifications are most important for external interfaces that must remain stable.

Software architecture

The architecture of a software system refers to an abstract representation of that system. Architecture is concerned with making sure the software system will meet the requirements of the product, as well as ensuring that future requirements can be addressed. The architecture step also addresses interfaces between the software system and other software products, as well as the underlying hardware or the host operating system.

Implementation (or coding)

Reducing a design to code may be the most obvious part of the software engineering job, but it is not necessarily the largest portion.

Testing

Testing of parts of software, especially where code by two different engineers must work together, falls to the software engineer.

Documentation

An important (and often overlooked) task is documenting the internal design of software for the purpose of future maintenance and enhancement. Documentation is most important for external interfaces.

Classification of computer software

The software is divided to System Software and Application Software with each having several sub levels.

System software is the low –level software required to manage computer resources and support the production or execution of application program.

Application software is software program that perform a specific function directly for the end user.

System Software includes

• Operating Systems software
• Network Software : network management software, server software, security and encryption software, etc.
• Database management software
• Development tools and programming language software: software testing tools and testing software, program development tools, programming languages software
• Etc.

Application Software includes

• General business productivity applications : software program that perform a specific function directly for the end user, examples include : office applications, word processors, spreadsheet, project management system ,etc.
• Home use applications : software used in the home for entertainment, reference or educational purposes, examples include games, home education etc.
• Cross-industry application software : software that is designed to perform and/or manage a specific business function or process that is not unique to a particular industry, examples include professional accounting software, human resources management, Geographic Information Systems (GIS) software, etc.
• Vertical market application software : software that perform a wide range of business functions for a specific industry such as manufacturing, retail, healthcare , engineering, restaurant, etc.
• Utilities software : a small program that performs a very specific task. Examples include : compression programs, antivirus, search engines, font, file viewers, voice recognition software, etc.