C Style Strings Chapter 5

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C Style StringsChapter 5
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C-style Character Strings in C/C

• Character strings are simply arrays of characters
• All character strings are assumed to be null
  terminated (end in \0 character)
• Leave room for the null character in the array
  declaration
• Literal character strings are in " "
  (individual characters are in ' ')

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Examples

• char firstName "Stephen"
• char lastName "Smith"
• These are strings of 8 and 6 characters
  respectively.
• Same as
• char firstName S, t, e, p, h,
  e, n, \0
• char lastName S, m, I, t, h,
  \0

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Output of character strings

• Output of literal or string variables to output
  streams will output all characters up to the null
  character.
• char bookTitle Rainmaker
• char authorName John Grisham
• cout ltlt The book is ltlt bookTitle
• ltlt by ltlt authorName ltlt endl

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Input of character strings

• Input of character strings is similar to input of
  other types - input values separated by white
  spaces
• char bookTitle10
• char authorName13
• cin gtgt bookTitle gtgt authorName
• if input is
• Rainmaker John Grisham
• then
• bookTitle is Rainmaker and authorName
  is John

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Input of whole lines of characters

• The extraction operator (gtgt) is not safe because
  if the input string has more characters than the
  variable, it reads anyway.
• The getline member function of the istream class
  can be used to read an entire line (including
  whitespace) into a string variable
• char line80
• cin.getline (line, 80 ,\n)

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Dangling newlines

• When numeric values are input, the following
  whitespace character is not processed

if input is 30 The next line then
string \n
int number char string80 cin gtgt
number cin.getline(string,80,\n)
Correct version string The next line
cingtgtnumber cin.ignore(80,\n) cin.getline(stri
ng,80,\n)
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C-style String functions

• Set of built-in functions for assignment,
  comparison, and other manipulation of character
  strings.
• You have to use
• include ltcstringgt

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Copying

• Cant use the assignment operator () to assign
  the contents of one character string to another.
• You can use the strcpy function instead.
• The format is
• strcpy(destString , srcString )
• Example
• strcpy(myName, yourName)

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Finding the Length

• The strlen function returns the length of the
  string.
• It doesnt count the null character
• Example
• strlen(Mahmood Hossain) returns 15

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Comparing Two Strings

• Cant use the comparison/equality operators to
  compare two character strings.
• You can use strcmp function.
• The format is
• int strcmp (char string1 , char string2
  )
• Returns
• 0 if string1 lexically string2
• -ve if string1 lexically lt string2
• ve if string1 lexically gt string2
• Example
• strcmp(Robinson, Roberts)

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Example

• include ltcstring.hgt
• void main (void)
• char myName Mahmood
• char anotherName30
• char otherName Jason
• strcpy (anotherName, myName)
• cout ltlt anotherName ltlt endl
• cout ltlt Length of my name is ltlt
  strlen(myName) ltlt endl
• if (strcmp (myName, otherName) 0)
• cout ltlt Names are the same ltlt endl
• else if (strcmp (myName, otherName) lt 0)
• cout ltlt myName ltlt precedes ltlt
  otherName ltlt endl
• else
• cout ltlt otherName ltlt precedes ltlt
  myName ltlt endl

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Arrays of Strings

• A string is a 1-D array of characters, so a 2-D
  array of characters would be an array of strings
• char names410 "Robert","Adam",
• 
  "Charles","Benjamin"

• This will declare an array of 4 strings with each
  string having a maximum of 10 characters
• names0 names1 names2 names3

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Converting strings to numbers

• Functions defined in ltcstdlibgt
• String to double
• double atof(char string)
• String to int
• int atoi(char string)
• String to long
• long atol(char string)
• Conversion begins at the first character and
  skips leading whitespaces
• Conversion ends at the first inappropriate
  character or the end of the string (null)