Write about Character Arrays (or) Strings? Explain how to Declare & Initialize Strings?

String: A string is a sequence of characters that is treated as a single data item. Any group of characters defined in between Double quotation marks is a string constant. Ex: “ degree college” If we want  to  include a double  quote in the string to be  printed, then we may  use it with a  back slash as: printf(“\”  well Done ! “\” ); Will out put  the string    “well Done” The common  operations performed on characters strings  include: . Reading & writing  strings . Combining  strings together . Copying one string for equality . Comparing strings for equality . Extracting a portion of a string.

Declaring and  initializing  string variables:

C  does not support  strings  as  a  data type. It  allows  us  to  represent  strings  as  character  arrays. A string  variable is any valid c variable name  & is always  declared as   a  array of characters. The general form of  declaration of  a string variable is : Syntax:  char  string_name [size] ; The size determines the number of characters in the string_ name. Ex: char city  [10];        char name[30]; When the compiler  assigns  a  character string  to a  character  array , it  automatically  supplies  a null character (‘\0’) at  the end of the string. Therefore the size should be equal to the maximum number of characters in the strings plus one. Like numeric arrays, character arrays may be initialized when they are declared. C permits two forms of initialization as: char city [9]= “New York” ; char city [9]=  {‘N’,’E’,’W’,’  ‘,’Y’,’O’,’R’,’K’}; C also permits us to initialize a character array without specifying the number of elements. In such cases, the size of the array will be determined automatically, based on the number of elements initialized.  Ex : char string [ ] = { ‘G’, ‘O’, ‘O’, ‘O’, ‘\0’};

Defines the array string as a 5 elements array. We can also declare the size much larger than the string size in the initialization i.e. char str [10] = “GOOD”; In this case, the computer creates a character array of size 10, places the value “GOOD” in it, terminates with the null character, and initializes all other elements To NULL. G O O D \0 \0 \0 \0 \0

The following declaration is illegal. char str [3]= “Good”; This will result in a compile time error. We can separate the initialization from declaration. i.e char str [5]; str = “Good”, is not allowed. Similarly char s[4] = ‘abc’; char z [4]; z=s; is not allowed. An array name cannot be used as the left operand of an assignment operator. Reading strings from terminal: Using scanf Function: The input function scanf  can be used with %s format specification to read a stirring of characters. Ex: char add [10]; scanf ( “%s”,add); In case of character arrays , the (&) ampersand is not required before the variable  name. The scanf function automatically terminates the string that is read with a null character and the character array should be large enough to hold the input string plus null character. The problem with the scanf function is that it terminates its input on the first white space it finds. A white space includes blacks, tabs, new lines etc; We can also specify the field width using the form %ws in the scanf statement for reading a specified number of characters from the input string. Syntax: scanf (“%ws” name); Here, 2 things may happen. 1. The width w is equal to or grater than the number of characters typed in. The entire string will be stored in the string variables. 2. The width w is less than the number of characters in the string. The excess characters will be truncated and left unread. Ex: char name [10]; scanf (“%5s”, name); The input RAM will be stored as: R A M \0 ? ? ? The input KRISHNA will be stores as: K R I S H \0 ? ? ? ? Reading a line of text: Scan with %s or %ws can be read only strings without white spaces. i.e. they cannot used for reading a text containing more than one word. C supports a format specification known as the edit set conversion code %[..] that can be used to read a line containing a variety of characters, including whitespaces  Ex : char line [80]; scanf (“%[L\n]”, line); printf (“%s”, line); Will read a line of input from the keyboard & display the same on the screen.

Writing Strings to screen:- Using printf function:

We can use the printf function with %s format to print strings to the screen. The format %s can be used to display an array of characters that is terminated by the null character. Ex : printf (“%s”,  name); It can display the entire content of the any name. we can also specify the precision (field width) using a form %ws.

Ex : % 10.4 Indicates that the first 4 characters are to be printed in a field width of 10 columns.