Chapter 4 The Ghost in the Machine

Ghost in the Machine- software Open source- type of program that allows the source code of the software to be readily accessible to a variety of people. Under a license agreement, which often has very few restrictions, the source code can be used, modified, and redistributed within a group of people. Linus Torvalds-
• Linux creator
• Linux- operating system- opens source software
• Linux powers web servers, film, and animation workstations, scientific supercomputers, and a handful of handheld        
  Major categories of software:
1. Compilers and other translator programs enable programmers to create other software
• compilers a computer program (or set of programs) that transforms source code written in a programming language (the source language) into another computer language
2. Software applications serves as productivity tools to help computer users solve problems
• example of computer application programs- Microsoft Word, Photoshop, Paint, etc...
3. System software coordinates hardware operations and does behind-the-scenes work the computer user seldom sees
• can not see the result
The hardware in a computer system is equipped to produce whatever a user requests
• hardware produces your result
A fast, stupid machine
• programmers being with an algorithm: a set of step-by-step instruction written in a natural language, e.g. English
• algorithm- effective method for solving a problem using a finite sequence of instructions
• more instructional
• the steps are often ambiguous, error-prone generalities
• bound to make error because numerous number of steps
• the steps are translated into the vocabulary of a programming language

The Language of Computers

• machine language- numeric codes that represent data
• high level language- falls between machine language and natural human language
• compilers translate high-level language into machine language
• examples: Perl, Python, BeanShell, KOC, JScript, snarf,....
• computer translates the functions into terms it understands
• natural language resembles languages spoken by human

software applications: tools for users

- many software companies have replaced their printed documentation with:

1. tutorials
2. reference materials
3. help files
4. online help

upgrading: users can upgrade a program to the new version by paying an upgrade fee to the software manufacturer

• newer releases often have additional features and fewer bugs

compatibility

- allows software to function properly with the hardware operating system, and peripherals

- programs written for one type of computer system may not work on another

- a hardware needs a compatible software

disclaimers

• software manufacturers limit their liability for software problems by selling software "as is"
• licensing commercial software is copyrighted so it cant be legally duplicates for distribution to others can't use it illegally
• software license
• volume licenses
• distribution of software is
• direct sale
• retail stores
• maul-order catalogs
• web sites
• not all software is copyrighted
• public domain software
• shareware

Web Applications- an application that is accessed by a web browser over a network

- web connectivity- connecting

-use web's strength as huge repository of information

-online business transactions

- up-to-the-minute reports on a myriad of subjects

- traditional form of information broadcasting

- -> web applications are used to type in messages into the Internet

integrated application and suites: software bundles

• vertical-market custom software
• cost more than mass-market applications
• jobs-specific software
• billings
• cataloging
• reference software
• managements

the hardware-software connection

-system software- class of software the  operating system and utility programs handling numerous behind the scenes program

utility programs- tools for system maintenance

• repairs damaged data files
• copy files between storage devices
• translates files so other programs can read them
• defends against viruses and other harmful program
• compresses file- to take less space

device drivers- small program enabling input and output devices- keyboard, mouse, printer, etc- to communicate with the computer

operating system is either stored in ROM or part of it

--remainder of the operating system is loaded into memory in a process called booting, occurs when you turn on computer

- usually works behind the scenes

 user interface-  a program that controls a display for the user (usually on a computer monitor) and that allows the user to interact with the system

--interacting with the computer

--Microsoft Disc operating system user interacts by using letters, numbers, and symbols

human-machine connection

• command-line interface- typing
• menu-driven interface - on-screen list commands

graphical user interfaces (GUI)

• Mac
• Microsoft Windows

examples of UNIX- Solaris, neXTSTEP,...