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Handling of Character Strings

Posted By: Hildemare Miller     Category: C Programming     Views: 4052

This article explains about handling of character strings in C programming.

-  A string is an array of characters in C
-  Any group of Chars in “” is a string const
-  \” for including double quotes in const
-  Common Operations performed are
  • Reading and writing
  • Combining, copying and comparing
  • Extracting portion of it

Declaring and Initializing

  •  char string_name[size]
  •  Here size should be no of characters + 1
  •  While supplying a string to a char array, compiler auto adds null char  at the end
  •  char city[5]= “Surat”
  •  char city [5]={‘S’,’u’,’r’,’a’,’t’,’\0’}
  •  Size can be omitted while initializing

Writing Strings using %s and %w.ds

  • %s and %w.d s
  • When w is zero, nothing gets printed
  • The runtime provision for w and d with printf( “%*.*s”, w,d, string) specification
  • It’s handy in printing sequence of characters for a given string in style
  • Minus sign for left justification

Arithmetic Operation on Chars using atoi() function

  •  char ch=‘a’; printf (“%d”,ch) will print 97
  •  x = ‘z’ – 1 assigns 121 to x
  •  ch >=‘A’ && ch <=‘Z’
  •  x= character – ‘0’ converts a character digit to it’s equivalent digit
  •  atoi is a function which converts a string of digits to a number

Putting String Together

  •  string1 = string 2 is invalid!
  •  string 3 = string1 + string2 is invalid!
  •  Need to write special routines to concatenate two or more strings
  •  if (name1 == name2) or (name1 = “Jay”) are invalid expressions for  string
  •  C has a rich set of string manipulation functions 

Few String Handling Functions


strcat(str1,str2) Statement

  •  part1 = very \0  part2 = good\0 
  •  part3 = bad\0
  •  After Execution of strcat(part1,part2)
  •  part1= very good\0   part2 = good\0
  •  str1 must be large enough!
  •  Nested strcat like strcat(strcat(str1,str2),str3 ) is allowed, result  is stored in str1

strcmp() Function

  • It compares two strings identified by the arguments and returns 0 if they are equal
  • If they are not, it has the numerical difference between the first non matching characters in the string
  • strcmp(“their”,”there”) will return –9 because it’s the difference between ASCII value of i and ASCII value of r

strcpy() Function

  • It acts as a string assignment operator
  • It takes the form strcpy(string1,string2)
  • It assigns the contents of string2 to string1
  • string2 can be a string constant like strcpy(string1,”Delhi”)
  • strcpy(city1,city2) will assign contents of city2 to city1

strlen() Function

  • This function counts and returns no of characters in a string
  •  n = strlen(string1)
  • Here n is an integer variable which receives the value of length of string
  • The argument may be a string constant
  • The counting ends at the first null character

Table of Strings

  • List of names of employees of a company, list of names of students etc are needed
  • student[30][15] can be used to store 30 student names of max 15 chars

Easier Way to Store Names

 static char city[][]

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Hildemare Miller
Hildemare Miller author of Handling of Character Strings is from Frankfurt, Germany.
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