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Handling of Character Strings

Posted By: Charlie Evans     Category: C Programming     Views: 9684

This article explains about string handling functions 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 

  • %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 

  •  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

Function Action
strcat() Cancatenate two strings
strcmp() Compare two strings
strcpy() Copies one string over another
strlen() Finds the length of a string

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
C h a n d i g a r h
M a d r a s
M u m b a i
A h m e d a b a d
H y d r a b a d


Easier Way to Store Names

 static char city[][]
{“Chandigarh”,
“Madras”
“Ahemdabad”,
“Hydrabad”
“Mumbai”
};
  
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Charlie Evans
Charlie Evans author of Handling of Character Strings is from London, United Kingdom.
 
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