Lecture 17 - Strings

Lecture 17 - Strings

• 1.
  Strings Md. Imran HossainShowrov (showrovsworld@gmail.com) 17 1
• 2.
  Outline  What isa String?  Defining A String  What is NULL Character?  Initialization of a String  Reading and Writing a String
• 3.
  What is aString?  The array represents a list of elements of the same data type.  Most of the programming languages handle array of characters with a special provision for stings.  Strings are actually one-dimensional array of characters terminated by a null character (represent as '0‘).
• 4.
  What is aString?  null character is also named as string termination character. It is used to identify the length of the string  Initially, the string is nothing but an array of individual characters, and each individual element is accessible via subscripts.
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  Defining A String A string definition may be expressed as storage-class char string-name [expression]; Example: char greeting[6] = {'H', 'e', 'l', 'l', 'o', '0'};
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  String Example1 char name[50]; /*name is a string that can consist of maximum 50 characters */ static char address[100]; /* address is a static string of maximum 100 characters */
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  String Example2 char greeting[]= "Hello"; Following is the memory presentation of the above defined string in C/C++  Actually, we do not place the null character at the end of a string constant.The C compiler automatically places the '0' at the end of the string when it initializes the array.
• 8.
  What is NULLCharacter  One of the most important issues in handling strings is null character.  Null character is used to terminate the string.  It is needed to compute the actual length of the string.  The string definition specifies the maximum length support. i.e. 50 in case of name[50] defines the maximum length of name.
• 9.
  What is NULLCharacter (cont..)  Example: char name [50] = “Jitender”;  In this example, the length of actual stored string is 8. In that case 9th element of the array i.e. name[8] location will be used to stored null character. J i t e n d e r ‘0’ …………… [0] [1] [2] [3] [4] [5] [6] [7] [8] [49]
• 10.
  What is NULLCharacter (cont..)  The null character is not counted towards the length of the string, but takes memory of one element.  Null character cannot be read or written, but is used internally only.
• 11.
  Initialization of aString  The string can be initialized as follows: - char str[30] = “Hello World”; char str[30] = {‘H’,‘e’,‘l’,‘l’,‘o’,‘ ’,‘W’,‘o’,‘r’,‘l’,‘d’}; H e l l o W o r l d 0 ………….. str [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [29]
• 12.
  Reading and Writinga String  A string can be read and written by using a single scanf and printf function using %s (s stands for string) and no loop in needed, which was compulsory for reading and writing arrays of other types.
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  Reading and Writinga String (Example) #include<stdio.h> #define MAX_SIZE 50 main() { char str [MAX_SIZE]; printf(“Enter a string of maximum %d characters: ”, MAX_SIZE); scanf(“%s”, str); /* no ampersand (&) is used here*/ printf(“The entered string is %sn”, str); }  After the reading is complete, the null character is appended automatically at the next position inside the array.
• 14.
  Processing the String Functionsare used to process with help of string.h header file or by processing all characters individually. 1. int strlen (string_var): to compute the length of the string, not counting null character. 2. strcpy (dst_string, src_string): to copy a source string into destination string 3. int strcmp(str1, str2): to compare str1 with str2 4. strcat(dst_string, src_string): to append copy of the source string at the end of destination string Here, dst_string = destination string src_string = source string