Distance Learning Center

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Distance Learning Center

• Lecture 12
• C Programming Language with Applications
• Melissa Lin, IT Consultant
• HenEm, Inc. Parkville, Missouri
• linm_at_ipfw.edu
• http//www.etcs.ipfw.edu/linm

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Lecture 12 C Arrays

• C Arrays
• Array Characteristics
• Types of Arrays
• Array Definition and Declaration
• Array Examples

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Array Characteristics

• Array Characteristics
• For grouping related data of the same type under
  one name
• Elements of an array are stored sequentially in
  memory
• The size of the array must be known at the time
  the array is allocated
• To refer to particular location or element within
  the array, specifying the name of the array and
  the subscript

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Array Characteristics (continue)

• Syntax int cN
• Arrays name is the base address or pointer to
  the beginning location of the array
• An array subscript is enclosed in a pair of
  brackets and always counted from 0 to n 1
• First element of an array - c0
• Second element of an array - c1
• The brackets used to enclose the subscript of an
  array.

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Array Characteristics (continue)

• Syntax int cN
• Arrays
• Character arrays, Integer arrays, Float arrays,
  etc
• Character array, the last location is reserved
  for \0 (null character)
• integer and float arrays, all the locations can
  be used for holding data
• Out of array boundary checking
• not performed automatically
• it is the responsibility of C programmers.

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Array Characteristics (continue)

• Example int array c10 / contains 10
  elements /
• c0 -45
• c1 6
• c2 0
• c3 72
• c4 1543
• c5 -89
• c6 0
• c7 62
• c8 -3
• c9 1
• printf(d, c0 c1 c9) /print
  the sum of the array /

Array name c
Position of the element within array c
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Types of arrays

• Array of integers
• Array of floating point numbers
• Array of characters String array
• Array of pointers
• Multi-dimensional array
• type array_namesizesize ..size

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Defining Arrays

• Array definition
• data-type array-namesize
• example int c100
• Elements of an array can be initialized in a
  definition, assignment, input from keyboard, etc
• A character array can be initialized using a
  string literal, or character constants
• All strings in C with a null character \0

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Array Declarations

• Arrays declaration
• It must be declared before use
• The purpose of defining integer arrays - inform C
  compiler the memory storage needed
• Dimensions of arrays declaration
• One-Dimensional Arrays
• Two-Dimensional Arrays
• multiple-Dimensional Arrays

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Array Declarations (continue)

• Examples of Declaring 1-D Arrays
• char name30 / 29 characters /
• char buffer1024 / 1023 characters /
• int rpm100 / 100 elements /
• int io_channel10 / IO channel /
• float pid3
• / 3 parameters for Personal ID Number /
• char device_name1010 /10 string arrays/
• char device10 / a pointer array /

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Two Dimensional Arrays

• An image array
• unsigned char image256256
• / 8-bit gray level, image array /
• Define a 2-D character array that can be used for
  displaying 2-by-20 characters
• define ROW 2
• define COL 20
• char display_LCDROWCOL
• display_LCD00 address of the element at
  row 0 col 0
• display_LCD019 ... address of the element at
  row 0 col 19
• display_LCD10 address of the element at
  row 1 col 0
• display_LCD119 address of the element at
  row 1 col 19

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Two Dimensional Arrays (continue)

• define ROW 100
• define COL 5
• int data_tableROWCOL
• data_table00 addresses of the element at
  row 0 col 0
• data_table01 address of the element at row
  0 col 1
• data_table10 address of the element at row
  1 col 0
• data_table11 address of the element at row
  1 col 1

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Initializing Arrays

• Examples
• static int d_array3 1, 2, 3
• static int parts_bin 100, 120, 200, 300, 400,
  120
• // parts_bin0, parts_bin1, ..
• static char string5 WXYZ
• static char string5 W, X, Y, Z,
  \0

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Initializing Arrays (continue)

• Muit-dimensional arrays (more than 1-D)
• define ROW 2
• define COL 2
• static int dataROWCOL 0, 1, 2, 3
• / Initialize Four 2-by-3 arrays /
• static int my_array423
• 1, 2, 3, 4, 5, 6,
• 7, 8, 9, 10, 11, 12,
• 13, 14, 15, 16, 17, 18,
• 19, 20, 21, 22, 23, 24

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Example 12-1 Initializing 2-by-20 LCD Display

• Initializing Array at run time using loop
  control
• / Initialize a 2D character array /
• define SIZE 2
• define LEN 20
• void main()
• char display_LCDSIZELEN
• int r, c
• for(r 0 r lt ROW r )
• for(c 0 c lt COL c)
• display_LCDrc \0

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Array Size Calculation

• If an array size is omitted from a definition,
  the number of elements in the array will be the
  number of elements in the identifier list.
• An example int n 1, 2, 3, 4
• an arrays size can be specified with a symbolic
  constant and initializing array elements
• example
• define SIZE 10
• int nSIZE

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Example 12-2 Initializing Arrays Using For Loop

• /Initialize the elements of array s to the even
  integers from 2 to 20 /
• include ltstdio.hgt
• define SIZE 10
• int main() / function main begins program
  execution /
• / symbolic constant SIZE can be used to
  specify array size /
• int s SIZE / array s has 10 elements /
• int j / counter /
• for ( j 0 j lt SIZE j ) / set the
  values /
• s j 2 2 j
• / end for /
• printf( "s13s\n", "Element", "Value" )
  //array s in tabular format
• for ( j 0 j lt SIZE j )
• printf( "7d13d\n", j, s j )
• / end for /
• return 0 / indicates successful termination
  /
• / end main /

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Example 12-2 Initializing Arrays Using For Loop
(continue)

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Example 12 - 3

• / char1.c - Manipulating character arrays /
• include ltstdio.hgt
• define SIZE 12
• static char phoneSIZE 260-481-1234"
• static char phone1 "260-481-1212"
• void main()
• int i
• char c

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Example 12 3 (continue)

• // A loop with counter for reading char array
• for(i 0 i lt SIZE i)
• c phonei
• putchar(c)
• putchar('\n')
• for(i 0 (c phone1i) ! '\0) i)
• putchar(c)

Output 260-481-1234 260-481-1212
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Example 12-4

• / for0.c - Working with integer arrays
  Initialize, /
• / copy and print contents of a and b
  arrays /
• include ltstdio.hgt
• define SIZE 10
• void main()
• int n, aSIZE, bSIZE
• /Initialize the a array with the index n 0,
  1, 2,.., 9/
• for(n 0 n lt SIZE n)
• an n
• / Initialize the b array with an 2 /
• for(n 0 n lt SIZE n)
• bn an 2
• printf("ad d, bd
  d\n",n,an,n,bn)

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Example 12 4 Output (continue)
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Example 12- 5

• / for1.c - Working with character arrays /
• / Print 'a'..'z', 'A'..'Z' /
• / Initialize lletter, and uletter /
• / Print the contents of arrays /
• include ltstdio.hgt
• define NEWLINE '\n'
• void main()
• int n int i 0
• char uletter27, lletter27

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Example 12 5 (continue)

• / Initialize char 'a' through 'z' for a lower
  case letter array /
• for(n 'a' n lt 'z' n)
• printf("c", n)
• lletteri (char) n // Type casting
• lletteri '\0' // Insert an End-of-string
  delimeter
• putchar(NEWLINE) i 0
• / Initialize char 'A' through 'Z' for a upper
  case letter array /
• for(n 'A' n lt 'Z' n)
• printf("c", n)
• uletteri (char) n

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Example 12 5 (continue)

• uletteri '\0'
• putchar(NEWLINE)
• / Reading two character arrays /
• for(i 0 uletteri ! '\0' i)
• putchar(uletteri)
• putchar(NEWLINE)
• for(i 0 lletteri ! '\0' i)
• putchar(lletteri)
• putchar(NEWLINE)

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Example 12 - 6

• / dowhile0.c - A do/while loop example that uses
  rand() function to generate testing data. /
• include ltstdio.hgt
• include ltstdlib.hgt
• define SIZE 10
• void main()
• int i
• unsigned r
• float sum, savingSIZE
• i 0 sum 0.0

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Example 12 6 (continue)

• do
• savingi rand() 1.0
• printf("savingd 8.2f\n",i,savingi)
• i
• while(i lt SIZE)
• i 0
• // summing saving array
• do
• sum savingi
• while (i lt SIZE)
• printf("Total saving is 8.2f\n", sum)
• puts("Hit any key to continue")
• getchar()

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Example 12 6 (continue)

• Output
• saving0 38.00
• saving1 7719.00
• saving2 21238.00
• saving3 2437.00
• saving4 8855.00
• saving5 11797.00
• saving6 8365.00
• saving7 32285.00
• saving8 10450.00
• saving9 30612.00
• Total saving is 133796.00
• Hit any key to continue

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Example 12 - 7

• / if1.c - Using if() statement to check if
  swapping is need. Swapping elements of an array
  /
• include ltstdio.hgt
• define SIZE 4
• static int a 2, 4, 9, 0
• void main()
• int i, temp
• // Print array before swapping
• for(i 0 i lt SIZE i)
• printf("ad d\t", i, ai)

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Example 12 - 7 (continue)

• for(i 0 i lt SIZE -1 i)
• if(ai lt ai1)
• temp ai
• ai ai1
• ai1 temp
• // Print array after swapping
• puts("\n")
• for(i 0 i lt SIZE i)
• printf("ad d\t", i, ai)

Output a0 2 a1 4 a2 9 a3
0 a0 4 a1 9 a2 2 a3 0
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Summary

• C Arrays
• Array Characteristics
• Types of arrays
• Array definition
• Array Declaration
• Array Examples
• Next
• Passing array to functions
• Searching arrays
• Multiple subscription arrays

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Question?

• Answers
• Email linm_at_ipfw.edu