System Software and Operating Systems

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System Software and Operating Systems

• Chapter 3 in Computing Essentials 2000-2001
  (OLeary and OLeary)

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Hardware vs. Software

• Hardware consists of the parts of the computer
  you can touch
• keyboard, mouse, monitor, printer, drives,
  motherboard, CPU and so on
• Software is simply a set of instructions (a.k.a.
  a program), it tells the hardware what to do and
  when to do it

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Software within Hardware

• While the software (the instructions) are stored
  on chips or disks, it is distinct from them
• Analogy in the same way that a musical score is
  distinct from the paper its printed on or the CD
  recording of it
• Hardware is the part of the computer you can
  kick if you can only curse at it its software

4
Interface

• An interface is a boundary or region of contact
  between two entities and typically where any
  interaction or exchange takes place
• The interface between the user and hardware is
  multi-layered
• There are interfaces within interfaces

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The various levels

• The layer closest to the user consists of
  application packages (like Word, Excel and
  PowerPoint) that help the user perform particular
  tasks and high-level languages (like C, Basic,
  Pascal, Fortran, etc.)
• the layer closest to the software is called the
  BIOS (Basic Input/Output System)
• In between lies the operating system

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BIOS

• The BIOS is a set of instructions stored on a
  read-only memory (ROM) chip
• It is sometimes called firmware since it
  occupies the middle ground between software and
  hardware. (The instructions are built right into
  the chip.)
• You may see the term BIOS on the screen soon
  after you turn on the power

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BIOS (cont.)

• It checks on (detects) the other parts memory,
  keyboard, mouse and so on
• Then it looks for the boot program that will
  load the operating system
• It always looks to the floppy disk drive first,
  which is why you shouldnt have a floppy in the
  drive when you are booting the system

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BIOS (cont.)

• While it is most noticeable during the boot
  process, the BIOS is used constantly
• This separation of BIOS from operating system
  allows for changes in hardware without a major
  rewriting of the operating system software

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Device Drivers

• If one has a new piece of hardware, the interface
  instructions connecting it and the operating
  system may not be written into the systems ROM
  chip, the software (as opposed to firmware) is
  needed
• This software is called a device driver

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The Vast In-Between

• Between the high-level (user friendly)
  applications and the BIOS is the system
  software, most notably the operating system but
  also language translators and utilities
• The operating system consists of programs for
  loading and executing applications, storing or
  retrieving files, managing the CPU, switching
  between tasks and so on

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Utilities

• File Viewer shows you the file or part thereof,
  esp. if its a graphic file
• File Conversion takes in one format and turns it
  into a another
• File Compression shrinks the size of stored
  files
• Backup makes a copy of your files in case of a
  system crash

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Utilities (Cont.)

• Diagnostics are things installed and working
  properly?
• Uninstaller gets rid of applications you no
  longer want
• Anti-virus seek and destroy virus, protection
  too
• Screen Saver it used to be that it literally
  saved the screen, now mostly entertainment,
  sometimes security

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Utilities and Language Translator

• Desktop Enhancer organizes desktop
• Internet manager manage your website
• LANGUAGE TRANSLATOR takes a programmers
  high-level code and converts it to a binary code
  that computer components understand. (Again
  this is done in several stages.)

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Op. Sys. Types of Interfaces

• Command-line interface the user types keywords
  (commands) after a prompt
• Menu-driven interface the user selects options
  from a menu typically using the arrow and Enter
  keys
• Graphical User Interface (GUI) the user points
  to icons with the mouse, etc.

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The kernel

• Especially with GUI interfaces, operating systems
  have become rather large
• Once the boot program is loaded into memory, it
  in turn loads the essential parts and the more
  frequently used commands (the kernel) of the
  operating system
• The rest (the external commands) are loaded only
  when needed

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Multi-this, Multi-that

• Operating systems may be distinguished in whether
  they allow
• multi-tasking
• multi-threading
• multi-users
• multi-processors

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Multi-tasking

• A task or process is a program or part of a
  program the user wants executed
• Modern operating systems are multi-tasking in
  that they execute two or more applications
  running simultaneously (actually they switch back
  and forth between the applications)
• Older single-tasking operating systems could only
  do one thing at a time

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Types of multi-tasking

• context switching only one process is active,
  but the status of the other process is preserved
• cooperative multitasking switching occurs at
  natural breaks in the process, but one
  application can take over
• preemptive multi-tasking tasks are prioritized
  and looked in on often so that one of them does
  not monopolize the CPU

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Multi-threading and Multi-user

• Multi-threading similar to multi-tasking but
  takes place within a single application, e.g. one
  wants to take in typed information and see it on
  the screen simultaneously
• Multi-user having more than one user, operating
  systems for work stations, mainframe, mini and
  supercomputers allow for more than one user

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Multi-processor

• If a single CPU is insufficient for your
  computing purposes, you may need an operating
  system which can coordinate a number of CPUs
  (processors)
• asymmetric different tasks assigned to different
  CPUs each with its own memory
• symmetric tasks and memory shared equally among
  CPUs

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System Management

• The operating system
• manages the processes
• manages the memory
• temporary storage (e.g. buffers)
• more permanent (e.g. disks)
• manages input and output
• manages security
• monitors performance

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Proprietary vs. Portable

• An important distinction in the business life of
  an operating system
• Proprietary limited to a specific vendor or
  computer model, marries software to specific
  companys hardware
• Portable will run on many different systems one
  can change hardware companies without changing
  software companies

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Some Operating Systems

• MS-DOS (Microsoft Disk Operating System)
• Windows 3.0 and 3.1
• Windows 95
• Windows 98
• Windows NT
• Windows 2000

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Some more OPs

• Macintosh
• OS/2
• UNIX
• NetWare