Aggregate Data Types

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Aggregate Data Types
Structuring the Data
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Aggregate Data Types

• Data Types that are designed to hold multiple
  values.
• Examples Arrays
• Strings
• Structures

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One Dimensional Arrays

• Used to store collections of data that are the
  same scalar type
• int array_110
• declaration of an array variable that will hold
  10 integers in positions from 0 to 9

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Accessing Array Positions

• Each array position is referenced through an
  index or subscript.
• array_10 15
• references position 0 of array_1

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Initializing an Array

• You can assign initial values to the positions in
  an array when the array is declared.
• char array_220 Hello there!
• initializes the first 11 positions of array_2 to
  the string Hello there!.

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Strings

• A string is simply a character array with a \0
  at the end (NULL or zero terminated).
• String constants must be enclosed in double
  quotes (Hello there).
• In C, a string must be created by assigning each
  individual position of the array with a character
  or using the C library functions.

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strcpy()

• strcpy copies from one string (or a string
  constant) to another string and adds \0.
• char deststr20, sourcestr20
• strcpy(deststr, sourcestr)
• strcpy(deststr, Hello there)

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strncpy()

• strncpy copies from one string (or a string
  constant) to another string a specified (n)
  number of bytes and adds a \0.
• char deststr20
• sourcestr20 John Doe
• strncpy(deststr, sourcestr, 4)

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strlen()

• strlen() returns the length of a string
• length strlen(my_string)
• strlen() can be used inside other function calls
• printf(The length is d, strlen(my_string) )

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strcat()

• strcat() concatonates two strings, one onto the
  end of the other.
• char result20 the result is
• strcat( result, the best ever!)
• the character array result ends up being
  the result is the best ever!

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STRUCTURES

• Designed to hold data of different scalar types

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Structure Declaration

• Example struct auto_part_tagS
• char id8
• float price
• int inv_num

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YOU Create a New Data Type

• Using the keyword struct followed by a tag and
  your definition of a new structure - is a
  structure declaration - it only creates a new
  data type. You still have not declared any
  variables of this type.
• Declare new structure data types globally, above
  main!

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Using Your New Data Type

• struct auto_part_tagS part1, part2, part3
  
• declares variables called part1, part2 and part3
  - they are each variables of the type of
  structure you created.
• Now, the variable part1 has room for an id, a
  price and an inventory count. So does part2 and
  part3.

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Accessing Members in a Structure

• Dot notation
• part1.inv_num gives access to the cur_inv
  member of the variable part1
• part1.inv_num 12
• strcpy(part1.id, JB-104Q)
• printf(This is inside a structure s, part1.id)

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Use a Structure as a Database

• Declare a structure data type above main
• Then declare several variables of that type
• This way, you can record data about many auto
  parts in stock, or many employees on your
  payroll, or many foot ball games held this
  season, etc...

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Use a Structure to Pass Parameters

• Declare a structure data type
• Declare a variable of that data type.
• Use the single variable to pass the whole
  structure as a parameter to another function.
• My_function(part1)

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LAB