CS 2130

1
CS 2130

• Presentation 02
• More Overview History
• Some C Stuff

2
Tests

• Test 1 Thursday, June 5, 2003
• Test 2 Tuesday, July 1, 2003
• Final Exam TBA
• Note The final exam schedule published at the
  beginning of the semester is tentative.
• Do not make plans around this tentative
  schedule!!!

3
Languages Translation

• Natural Languages
• English
• French
• Russian
• Japanese
• Esperanto
• Very complex rules of grammar
• Often ambiguous
• Usually tied to speech
• Constantly evolving
• Often very context sensitive

• Computer Languages
• Assembler
• Fortran, Cobol, Basic
• C, Ada, Forth
• Lisp, Scheme, SML
• Prolog
• Smalltalk, C, Java
• Grammars more structured than natural languages
• Precise?
• Not often spoken
• Fixed by version/standard
• Context free?

4
Languages Translation

• Converting one language into another
• We will deal with translation of computer
  languages
• Why do we need translation?
• Efficiency
• Abstraction (Want to write in HLL)

5
A Little History

• Beginnings (30's and 40's)
• Theoretical Foundations of Computer Science
• Turing, Godel, Church, Markov, Post, Kleene
• Binary logic/Idea of algorithms
• First electronic computers in 40's
• Programming by wiring then machine language
• Development of Programming (50's)
• Symbolic names
• Assemblers
• High Level Languages (60's)
• High Level Languages (e.g. Fortran/Cobol/Lisp)
• Data structures/Parameters
• Transportability?/Program as assembly of parts

C70600000002
MOV X,2
X 2
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A Little More History

• Program Size Complexity Increasing (70's)
• C and Pascal
• Recursion and Dynamic Memory
• Interactivity/Timesharing (80's)
• Software Engineering
• Object Oriented Approach Smalltalk C
• Network Prominence (90's)
• Internet/www
• Separate compilation
• Java
• Next???

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Translation by any other name...

• Compiler
• Translates program written in "source" language
  to "target" language
• Interpreter
• Translate and immediately execute
• Assembler
• Translate into machine language for particular
  machine
• Macro Processor
• Textual substitutions

8
Compilers

• Fortran
• .for ? .obj ? .exe
• C
• .c ? .o ? a.out
• Java
• .java ? .class
• Compilation often used for speed and efficiency
  of executable code

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Interpreters

• Emulators
• Basic
• Beginner's All-purpose Symbolic Instruction Code
• Lisp
• Scheme
• Java Virtual Machine
• Interpreters often used for educational/rapid
  prototyping and portability in the case of Java

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Assemblers

• Typically processor/machine specific
• Some compilers produce assembly code
• Very close tie to hardware
• Symbolic version of machine language
• Still used for speed/size in performance critical
  apps
• Needlepoint for nerds?

11
Macro Processors

• C Preprocessor
• Performs many useful tasks before "actual"
  compilation begins
• Macro substitutions
• C
• Initially a preprocessor translated C program
  into C program
• m4
• UNIX macro processor

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Other Items?

• Linkers
• Loaders
• Editors
• Debuggers
• Profilers
• Project Managers
• Instant Messengers
• Quake
• Jolt/etc.

13
C Programming

• 5 Weeks
• Not a C Programming course
• Focus on using for translation
• C as translation target
• Course designed to be taken at same time as ECE
  2030

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C Review

• BCPL (Typeless) - 1967 - Operating Systems
• B - Ken Thompson - First version of Unix
• C - 1972 - Dennis Ritchie - Implemented on PDP-11
• Unix rewritten in C in 1974
• Publication of "The C Programming Language" by
  Brian Kernighan and Dennis Ritchie
• ...
• ANSI C (1989)
• Major updates to C standard in 1994 and 1999
• We will use C89 in CS 2130 (GNU C compiler)

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C Stuff

• C Programs generally consist of one or more
  functions
• Execution starts in a function called main
• Arrays
• Start at 0
• No bounds checking
• Strings
• There are no strings...more later!
• Structures
• Like objects with only public fields i.e. no
  methods)
• Pointers
• Variable containing an address or location in
  memory

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More C Stuff

• Comments / /
• Types
• Character
• Integers
• Warning Hex constants...Octal Constants
• Long and Short
• Signed and Unsigned
• Floating Point
• Sizeof
• sizeof(int) / sizeof a type /
• sizeof x / sizeof a data object /

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Expressions

• A constant or variable by itself is an expression
• Combinations of constants and variables with
  operators are also expressions
• Examples
• 7 / Constant /
• x / Variable /
• x 7 / with operator /
• x x 7 / with operators /
• x x 7 / Simple statement /

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Operators

• Assignment Operator Evaluate expression on
  right, store result in variable on the left
• Add value on right side to variable on left
  side
• - Subtract value on right side from variable on
  left side
• Multiply variable on left side by value on
  right side
• Assignment expression itself has a value!
• a b c 0

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Other Operators

• Binary Arithmetic - /
• Unary - --
• Bitwise ltlt gtgt
• Relational lt lt gt gt !
• Logical !

Pretty much the same as Java except there is no
boolean value
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Common Pitfalls

• / Java /
• int foo(int x)
• for(int i0iltMAXi)
• ...

• / C /
• int foo(int x)
• int i
• for(i0iltMAXi)
• ...

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Common Pitfalls

• int foo(int x)
• int a
• int b 7
• int c
• c 9
• int d
• Cannot mix code and declarations...

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Questions?
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