Download Lecture 1: What is a Computer?

Lecture 1: What is a Computer?
Lecture for CPSC 2105
Computer Organization
by Edward Bosworth, Ph.D.
An Older Computer
The figure at right is an older computer, called
a PDP-11/20.
It was designed in the early 1970’s.
It shows the computer, with front-panel
switches, and a paper tape reader.
User interaction was via a teletype.
Basically, all one got was “bare iron” – the
hardware and very little software.
An ASR-33 Teletype
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.
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.
Sample Computer
My Wife’s Netbook.
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 i3–330UM, which
operates at 1.2 GHz. It is described by Intel as
“an Ultra Low Voltage dual–core processor
for small and light laptops”.
More Properties of the Computer
• It has a three–level cache. Each of the two cores has
a L1 (Level 1) cache (likely a 32–kilobyte 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 built–in GSM card for access to
the global Internet through the AT&T network.
The GUI
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
The Computer as an
Engine 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 understanding
computers.
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 operate
the CPU.
• The general-purpose registers available for
use by the programmer.
• The details of the I/O system.
Another View of the Computer
• The Operating System provides services that
use and augment the low level ISA
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
Moore’s 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.
Graph of Transistor Count
Picture Showing Moore’s Law
The Power Wall
The Power Wall (Part 2)
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”.
Sample C/C++ Program