Special Topics CP 772 Lecture 2 1

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Special TopicsCP 772Lecture 2 - 1
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Session Objectives
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Comments

• / Multi line comment /
• // Single line comment

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Keywords

• 62 C keywords
• Includes all 32 C keywords

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Identifiers

• Same rules as C
• no keywords
• Must start with a letter or underscore
• letters, digits, underscore only
• Double underscore __ for system use only
• Underscore capital _Y for system use only

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Literals

• Constant values
• 5
• 5u
• 05
• 5
• true
• A

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Operators

• Have meaning in context with appropriate
  arguments
• Has all of the C operators
• Has some of its own.

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Native Types

• char
• unsigned char
• signed char
• short
• int
• long

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Native Types(2)

• unsigned short
• unsigned
• unsigned long
• float
• double
• long double

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Native Types specific to C

• wchar-t
• bool

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Sizes

• Requirement is that each longer type be at least
  as large as its predecessor type.
• Range of integral values representable on out
  system contained in limits.h
• Range of floating point values contained in
  float.h

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Program Structure

• Collection of functions and definitions.
• Block structured

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Expressions

• Like C, basic unit of execution
• each expression has a value
• each expression has a type
• coercion required for mixed expressions
• expression terminated by a semi colon () is a
  statement

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Automatic Expression Conversions

• 1/ Any bool, char, short or enum is promoted to
  int. If unrepresentable as int then promoted to
  unsigned.
• 2/ then
• int lt unsigned lt long lt unsigned long lt float
• lt double lt long double

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Conversions with Assignment expressions

• D I // int promoted to double. Expression of
  type double
• I D // d narrowed to int - info lost.
  Expression of type int.

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Precedence

• If two or more operators involved in one
  expression then we need to know which operator
  will be invoked first
• Precedence rules help establish this

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Associativity

• When operands have equal precedence then
  associativity rules must be invoked

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Casting

• Programmer can explicitly force an expression to
  have a certain type
• (type) expression //C cast
• type (expression) //C cast

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Ansi C casting

• static_cast ltdoublegt (i)
• reinterpret_cast ltintgt (x)
• const_cast ltintgt (c_var)
• dynamic_cast ltintgt (c_var)

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Examples

• int p, q
• p new int(5)//allocation and initialisation
• q new int 10 //Array of 10 integers
• delete p // Deallocate p
• delete q // necessary for deallocating
  arrays

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Other concepts

• volatile
• enum

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Const

• Indicates that a variable or a function
  parameter has a non-modifiable value.
• const int hours_in_day 24
• const int p x
• int const ptr y