CSE 100: C Programming

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CSE 100 C Programming

• Partha Dasgupta

rhymes with Martha
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Recap

• For Loops
• While Loops
• Break and Continue
• Recursion is bad ?
• Disagree ?

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Caeser

• Friends, Romans, countrymen,
• lend me your ears
• I come to bury Caesar,
• not to praise him.

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C

• Friends, Students, Fellow Sufferers,
• lend me your ears
• I come to bury C,
• not to praise it.

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What is the big deal?

• C is one of the most popular programming
  languages
• Other than C
• C is an object oriented sugar coating of C
• Sugar cannot hide the underlying tart
• All programming languages that are better are
  essentially dead
• We love complexity and we hate to type
• It is all about power and obfuscation (job
  security too)

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A bit of history

• Machine Code
• Assembly Language
• A lot of languages, leading to FORTRAN and COBOL
• A parade of languages that died.
• Algol
• APL
• Snobol
• Pascal
• Modula
• PL/1
• ADA
• What lives on is C and C (with Java making
  inroads)

• Smalltalk
• Eiffel

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What is right about C

• Object Oriented
• Plethora of dynamic binding features
• Powerful, cryptic also the reason why its a
  problem language
• Almost as powerful as assembly
• Derived from C
• Not too easy to learn
• Touted benefits
• Readable code
• Highly structures
• Almost type safe with Standard Template Library
• Aside How to write code that is not vulnerable
  to attacks on the internet??

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So what is the problem

• Lack of a consistent, simple grammar
• Too easy to make trivial mistakes
• And exceptionally hard to find to them
• Too easy (and tempting) to write unreadable code
• The obfuscated C contest, also C
• Its like fire, cannot live without it, but it
  really can (and will) burn you
• Handle with care

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C Programming

• C Programming C Programming
• Program Algorithms Data Structures

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Algorithms

• Alice sends Bob to the supermarket
• How to express
• Conditionals (IF)
• Iterative (WHILE, FOR)
• Branching (GOTO)
• Recursive
• Variables Data Structures

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Data Structures

• How do you sort your socks?
• Arrays
• Structures
• Linked Lists
• Trees
• Hash Tables

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Grammar Anyone?

• Expression Grammar
• expr expr expr
• expr expr expr
• expr expr expr
• expr expr / expr // expr expr -/
  expr
• expr (expr)
• expr number
• expr term / expr
• expr term
• term factor - term
• term factor
• factor (expr)
• factor number

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Eclectic Stuff

• Can a program understand another program?
• SURE

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Eclectic Stuff

• The halting problem
• Does a routing halts exist that can decide if a
  program halts?
• programA (programB)
• if halts(programB)
• loop forever
• else exit
• Now what happens if we call
• programA(programA) // funny? or inspiring?