Introduction to Systems Architecture

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Chapter 2

• Introduction to Systems Architecture

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Chapter goals

• Discuss the development of automated computing
• Describe the general capabilities of a computer
• Describe computer system components and their
  functions
• List computer system classes and their
  distinguishing characteristics
• Define the role and function of application and
  system software
• Describe the economic role of system and
  application development software

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Why invent a computer?

• What kinds of problems were people trying to
  solve?

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Primary characteristics of a computer

• General-purpose processor capable of performing
  computation, data movement, comparison, and
  branching functions
• Storage capacity sufficient to hold large numbers
  of program instructions and data
• Flexible communication capability through the use
  of multiple media and devices

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Computer hardware
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CPU Architecture
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Storage Categories
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Input/output capacity

• PC is a varied collection of devices connected
  through internal communication (system bus)
• Readings from White on evolution of the system bus

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System bus

• How does capacity of system bus compare to CPU?
• Why is backwards compatibility an important
  issue for the bus?

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Computer System Classes

• Microcomputer/Network Computer (PC)
• Minicomputer (up to 100 simultaneous users)
• Mainframe (1000s of simultaneous users)
• Supercomputer (computationally intense
  applications weather forecasting, computer
  animation)

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Computer System Classes
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The Role of Software
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Complexity of software creation

• Software performs a complex translation
• Identified need or task
• Human language description of how to complete the
  task (algorithm, recipe, construction plan,
  blueprint)
• Algorithm to programming language (code)
• Programming language to machine language
• Machine language to CPU instructions (all binary,
  0s and 1s)

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Software types

• Application software
• System software

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Systems software

• Invisible to user (ideal)
• IS professional needs to understand/configure/in
  stall/maintain/update systems software

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Software layers
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Software/hardware layers
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System software layers

• System management utilities called by
  user/system administrator
• System services functions common to many
  applications carried out by system software
  (print)
• Resource allocation manage multiple requests
  for same resource
• Hardware interface carries out instructions
  that operate directly on devices (device drivers)

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Machine independence

• Layers hide specific details about hardware
• Standard service requests (print) are translated
  at lowest possible level to specific hardware
  instructions
• Example adding a new printer changes your OS,
  not every application installed on your machine

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Machine independence (cont.)

• Placing all hardware interface functions within a
  single system software layer
• Concept of virtual machine (used by Java, .NET)
• Same applet is downloaded
• Each individual machine (unix, mac, windows) has
  own systems level to carry out instructions from
  applet

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Operating systems functions

• Program storage, loading and execution
• File manipulation and access
• Secondary storage management
• Network and interactive user interfaces

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Application development

• Toolkit or suite to assist in development of
  software
• Referred to as Integrated Development Environment
  (IDE)
• Programs that helps create other programs

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Application development (cont.)

• IDE consists of
• Program translator (compiler)
• Program editors
• Debugging tools
• System development modeling tools (CASE
  computer aided software engineering)

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Computer networks

• Set of hardware and software components that
  allows information, software and hardware
  resources to be shared among multiple users and
  computer systems

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Network components

• External Resources
• Network Software
• Network Communication and the Physical Network

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Chapter summary

• This chapter introduces the primary topics of the
  text
• Hardware
• Processor
• Software
• Operating systems
• Networks