Systems and User Interface Software

Types of Operating System  Single User  Multi User  Multi-tasking  Batch Processing  Interactive  Real Time  Distributed Processing

Single User  An operating system designed for use by only one user at a time.  This would be the operating system found on a standalone PC.

Multi User  More than one user using the computer at a time  Computer connected to a number of terminals  O/S allocates a time slice to each user and travels from user to user.  The larger the number of users the slower the system works

Multi Tasking  Allowing several program to be loaded and apparently running at the same time.  Each program is kept in a separate memory area and the computer allocates peripherals in the most economic way.  True multi tasking requires more than one processor.

Batch Processing  Transactions collected and stored.  When all have been collected they are processed at the same time.  Suitable for situations where there is a lot of data to be processed and the processing can wait.  It is not suitable for situations where the data must be processed instantly.

Interactive  Direct user interaction whilst a programming is running  “Question and answer” between user and computer  Cannot be used in batch processing  Computer gives the user an immediate response  For example Booking systems

Real Time  Must respond to real time events with no discernable delay  Interrupts are guaranteed to be handled within a certain specified maximum time  Used for control systems such as traffic lights, air traffic control, aircraft navigation  Used for embedded systems (systems within another application, e.g. cars and mobile phones)

Distributed Processing  A series of computers connected together  Each computer performs part of the processing  When all of the results from individual machines are put together you end up with complete processed data. Frees the central computer Faster local processing Not affected by breaks in system

Styles of Interface  Command Based  Forms  Menus  Natural Language  Graphical User Interface  WIMP

Command Based  Command Prompt  Commands are typed  Each command can have switches These are different modes in which the command can be run: »Dir gives a directory listing »Dir /w gives the listing across the page »Dir /s includes the sub directories »Dir /p pauses at the bottom of every page  Expert users only

Forms  Data Labels giving assistance  Boxes to enter/choose data  Used for Data entry (records)  Making choices is easier  The user is given choices  Useful for novice users

Menus  Series of related items which can be clicked  Presents a limited choice  Novice friendly  Structured into options

Natural Language  User types or speaks in normal everyday language and the computer responds  Used in Microsoft Help and Ask Jeeves Web Site  Useful for novice users as they do not need to understand the computer to use it.  With vocal input, useful for physically handicapped people.

Graphical User Interface  Describes the interface between the user and the computer.  Replaces some of the text with images  May incorporate menus, forms and commands

WIMP  Windows  Icons  Mouse/Pointer  Menu/Pull Down Menu

Applying User Interfaces to Users  Different users have different requirements: Visually Impaired: »Mouse tails, screen magnified, contrasting colour schemes, large icons etc. Expert users: »Command line, short cut keys, programming add-ons Location: »Touchscreen interface, concept keyboard, etc Physically disabled: »Additional input devices require changes to the user interface

Self Documenting Systems  Systems where no external documentation is necessary  Includes: Tool Tips Internal help guides Meaningful variable names Commented code On-line help Informative error messages

Supplementary User Documentation  Documentation which comes “in the box” with the computer and/or the software  Includes: Start-up guide Warranty guide Health guide Quick start guide Troubleshooting guide Glossary Technical Reference Manual Tutorial

Utilities and Systems Software  Utilities Assist the user in the use of the computer Individual programs which carry out minor tasks – formatting hard drive, moving files, anti-virus, compression.  Configuration files Used to tell the computer how a particular piece of hardware or software is to be run. This sets up options such as where the program is located, the window size, etc. It changes the hardware or software from being generic to being specific to the environment in which it will be working.

Utilities and Systems Software (cont.)  Drivers Handles communication between the Operating System and the device. Each peripheral needs a device driver to work. It translates information from the computer into a format understood by the device.  Compression Software (data transmission) Data takes up a lot of storage space. It can be compressed to take up less space. When you compress data to decrease its size, it then takes longer to access. Compression is used for archive and backup files. It is also used to send files. If you compress a file before sending, it will send quicker than an uncompressed file.