Lecture 1: What is a Computer?

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Lecture 1 What is a Computer?

• Lecture for CPSC 2105Computer Organizationby
  Edward Bosworth, Ph.D.

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An Older Computer

• The figure at right is an older computer, called
  a PDP-11/20.
• It was designed in the early 1970s.
• It shows the computer, with front-panelswitches,
  and a paper tape reader.
• User interaction was via a teletype.
• Basically, all one got was bare iron the
  hardware and very little software.

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An ASR-33 Teletype
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A Modern Computer as a System

• A modern computer must be seen as a complete
  system software hardware.
• The hardware and software must be designed as a
  complete system.
• Software includes the operating system and
  compilers to convert higher level languages to
  the primitive assembly language.

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User Experience of a Computer

• There are a number of factors affecting the user
  experience of a modern computer.
• 1. The choice of operating system.
• 2. The GUI (graphical user interface).
• 3. The physical size of the computer itself.
• What is not a factor includes the detailed design
  of the CPU and other hardware.

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Sample ComputerMy Wifes Netbook.
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Some Properties of the Computer

• It is approximately 11 inches by 7.5 inches.
  When closed it is a bit less than one inch
  thick. This CPU model was introduced in the
  second quarter of 2010. It is made in China.
• The CPU is an Intel Core i3330UM, which operates
  at 1.2 GHz. It is described by Intel as an
  Ultra Low Voltage dualcore processorfor small
  and light laptops.

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More Properties of the Computer

• It has a threelevel cache. Each of the two
  cores has a L1 (Level 1) cache (likely a
  32kilobyte split cache, with 16 KB for
  instructions and 16 KB for data), and a 512 KB L2
  cache. The two cores share a common 3 MB L3
  cache.
• The computer has 2 GB (2,048 MB) of DDR3 memory.
• The computer has a 256 GB hard disk and two USB
  ports that can be used for USB flash drives.
• The display is a 1366 by 768 LED LCD.
• The computer has a builtin GSM card for access
  to the global Internet through the ATT network.

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The GUI
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The Computer As An Appliance

• Most users of a computer view it as an appliance
  just a machine that does things.
• Provides e-mail
• Runs Facebook and other social media
• Runs applications, such as MS-Word, etc.
• The computer is seen as a complete system,
  without thought of its piece parts.
• This is one of our great achievements in CS

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The Computer as anEngine for High-Level Languages

• This is the view of many programmers. It also is
  quite valid.
• The computer allows a Java program to run, accept
  input and produce output.
• This is also a valid approach to
  understandingcomputers.

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Computers from the Bottom Up

• At the lowest level of concern to this course,
  the computer is characterized by its ISA, the
  Instruction Set Architecture.
• The primitive instructions that operatethe CPU.
• The general-purpose registers available foruse
  by the programmer.
• The details of the I/O system.

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Another View of the Computer

• The Operating System provides services thatuse
  and augment the low level ISA

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IBM System/370 Assembler

• Here is some code, with System Calls in Red
• PUT PRINTER,PRHEAD
• GET FILEIN,RECORDIN
• LOOP MVC DATAPR,RECORDIN
• PUT PRINTER,PRINT
• GET FILEIN,RECORDIN
• B LOOP

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Moores Law

• Gordon Moore, one of the founders of the Intel
  Corporation, made an observation about the
  density of transistors on a computer chip.
• He noted that the count would double about every
  18 months or two years.
• This observation has held true for about four
  decades, so it is now called a law.

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Graph of Transistor Count
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Picture Showing Moores Law
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The Power Wall
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The Power Wall (Part 2)
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The C/C Language

• We shall write a few small programs and use a
  debugger to examine the internal structures.
• The language will be the older C language, with a
  few C features. We shall use the C compiler,
  which is more convenient.
• This will be C without objects.

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Sample C/C Program