Program structure and computer architecture

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Program structure and computer architecture
Jan. 10
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Hackers Tip of the Day Moores Law
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Cost of RAM
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Cost of Hard Drive Space
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(No Transcript)
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QUIZ!

• In your own words, describe in one sentence what
  a compiler does
• What is the name of the compiler that we will be
  using this semester?
• Suppose we just wrote a program and saved it in a
  file called hello.c. What command would you use
  to compile it?
• What command would you use to create a new
  integer variable called movieCount that has a
  value of 107?

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Answers

• A compiler converts a plain text file containing
  a computer program into an executable file that
  the computer can run.
• gcc
• gcc Wall o hello.exe hello.c
• int movieCount 107

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30-Second Survey

• Attempted to get Cygwin/Mac Developer tools
  installed?
• Succeeded?
• Got emails sent to class email list?
• Know how to convert between decimal and binary
  numbers?

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News

• Textbook wont be available from the bookstore
  for a while.
• Recommendation get it from Amazon (its cheaper
  there anyway)?
• Windows Vista users
• New tutorial about getting Linux working on Vista
• Link available from the course webpage
• Good text editor for Windows
• Notepad

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Computer Architecture
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Input/Output Devices
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I/O Devices
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Long Term Storage
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Long Term Storage

• Data remains intact when computer is shut off
• Relative Access speed Slow
• Access requires physical movement
• Hard drive disk has to physically spin to
  read/write data
• DVD-drive physically whirs up DVDs to 52X speed
• Flash drives are the exception (no moving parts)?
• Relative Cost Per Byte Low
• 500 GB harddrive 75 ( about 7 GB per
  dollar )?
• 500 DVD-R 100 ( over 2 TB )?

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Short Term Storage Working Memory (RAM)?
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Working Memory/RAM

• Volatile data is lost when computer is shut off
• Relative Access Speed Medium
• No moving parts like some persistent storage
  mechanisms
• Relative Cost Per Byte Medium
• 4 GB of DDR2-667 300 ( 14 MB per
  dollar)?

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CPU Central Processing Unit
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CPU Central Processing Unit

• Performs all actual calculations
• Has a relatively small set of low-level
  instructions
• Add two numbers
• Multiply two numbers
• Load a number from memory
• Store a result into memory
• Jump to a different instruction to execute

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CPU Cache (L1, L2, L3 cache)?

• Small amount of working memory built right onto
  the CPU (sometimes called onboard cache)?
• Relative Access Speed Fast
• Close proximity to CPU leads to very little delay
  to store and load data
• Relative Cost Per Byte High
• A modern computer might have a 1 MB L2 CPU cache

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CPU Registers

• Tiny amount of memory built directly into the CPU
• Registers typically store only the data that is
  being used for the single operation that the CPU
  is currently working on
• Relative Access Speed Ultra Fast
• Relative Cost Per Byte Ultra High
• Several hundred bytes per CPU

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Buses
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Buses

• Connect different parts of the computer together
• Allow communication between devices
• The faster the bus, the faster information can be
  sent along

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Storage Sizes Bit

• Store only 1 of two values
• 0 or 1
• Off or On
• False or True
• You can store the answer to any yes/no question.
  But thats it.

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Storage Sizes Byte

• 1 byte 8 bits
• Store values from 0 to 255 (hint 28 256)?
• Store any single keyboard character
• 00000000 a
• 00000001 b
• 00000010 c
• 00000011 d

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Storage Sizes Kilobyte

• 1 KB 1024 bytes
• Kilo is from latin meaning one thousand
• A paragraph or two of plain text
• A very simple webpage

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Storage Sizes Megabyte

• 1 MB 1024 KB
• One rather high quality digital photograph
• 1 minute of high quality MP3 (music quality)?
• 5 minutes of low quality MP3 (spoken word
  quality)?
• Several hundred pages of text

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Storage Sizes Gigabyte

• 1 GB 1024 MB
• Are you noticing a pattern?
• 3000 nice quality digital photographs
• 200 high quality music MP3s
• 5 minutes of high quality digital video

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Storage Sizes Terabyte

• 1 TB 1024 GB
• 200,000 MP3s (more songs than youve ever heard)?
• 100 full length DVD quality movies

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Storage Sizes Petabyte

• 1 PB 1024 TB
• Entire Library of Congress is estimated at about
  3 PB

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Storage Sizes Exabyte

• 1 EB 1024 PB
• Every word ever written, spoken
• Every picture ever taken
• Every sound recording
• Every video ever shot

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Storage Sizes Zettabyte

• 1 ZB 1024 EB
• Every inch of the earths surface to be monitored
  with HD video for all human existence

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Program Structure
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Source Code (hello.c)?

• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• return( 0 )

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Include a library for printing to the screen

• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• return( 0 )

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stdio stands for standard input/output
Include a library for printing to the screen

• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• return( 0 )

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main function program always starts here

• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• return( 0 )

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input into the main function don't worry...just
copy/paste
main function program always starts here

• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• return( 0 )

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Opening curly braces beginning of a block of
code

• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• return( 0 )

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Opening curly braces beginning of a block of
code

• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• return( 0 )

Closing curly braces end of main function block
of code
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• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• return( 0 )

Statements inside of braces instructions for
program
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Semicolon is required at the end of each
instruction

• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• return( 0 )

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• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• printf( "I already said hi!\n" )
• return( 0 )

Statements execute in sequential order
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• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Value is d\n", x )
• int x 10
• return( 0 )

Statements execute in sequential order
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• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Value is d\n", x )
• int x 10
• return( 0 )

Statements execute in sequential order
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• include ltstdio.hgt
• int main( int argc, char argv )?
• printf( "Hello, World!\n" )
• return( 0 )

Return goes at end of main function copy/paste
for now
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printf Function Displaying Text on the Screen

• printf( "Hello, World!\n" )

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printf Name of function

• printf( "Hello, World!\n" )

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Quoted text (with double quotes) to be printed out

• printf( "Hello, World!\n" )

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\n Special character that prints out a new line
(like pressing enter)?

• printf( "Hello, World!\n" )

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Oops, forgot the new line character

• printf( "Hello, World!" )
• printf( "How are you?" )

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d Special marker to substitute in a variable
value into the printout

• int x 50
• printf( "The value is d\n", x )

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The name of the variable to be substituted into
the d

• int x 50
• printf( "The value is d\n", x )

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Operations with Variables

• Symbols for different mathematical operators
• for addition
• - for subtraction
• for multiplication
• / for division

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include ltstdio.hgt int main( int argc, char
argv )? int x 3 int y 0 y x 2
printf( The value of y is d\n, y ) return(
0 )
x and y Two different variables
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include ltstdio.hgt int main( int argc, char
argv )? int x 3 int y 0 y x 2
printf( The value of y is d\n, y ) return(
0 )
Assign y a new value
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include ltstdio.hgt int main( int argc, char
argv )? int x 3 int y 0 y x 2
printf( The value of y is d\n, y ) return(
0 )
Print out new value of y