This document provides an overview of using strings and character arrays in C programming, including declaration, initialization, memory allocation, and methods for reading strings from user input. It describes various string handling functions from the string.h library such as strlen, strcpy, strcat, strcmp, strlwr, and strupr. Additionally, it introduces structures as a user-defined data type for combining different data types, exemplified by keeping track of books in a library.

1. Declaration
• A string variable is declared as an array of characters.
Syntax:
char string_name[size];
e.g. char s[5];
• When the compiler assigns a character string to a
character array, it automatically supplies a null character
(‘0’) at the end of the string
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2. Initialization
Initialization Syntax:
char myString [] = { 'H','A','E','S', 'L', 'E', 'R', '0' } ;
char myString[13] = “Initial value”
char myString[] = “Initial value”;
0 = null character
Note: that ‘0’ and ‘0’ are not same.
• When we initialize a character array by listing its elements, the null
terminator or the size of the array must be provided explicitly.
• When declaring a string don’t forget to leave a space for the null
character which is also known as the string terminator character
because it is only way the functions that work with a string can know
where the string ends.
n i t i a l v a l u e ? ? …
I 0
Compilation time
initialization
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3. Differences Between Strings and Character
Arrays
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4. • Memory for strings must be allocated before the string can be
used.
• A string literal is enclosed in double quotes
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5. Reading String from terminal
• Input function scanf can be used with %s format specification to
read in a string of characters.
• Example: char address[10]; scanf(“%s”, address);
• The scanf function automatically terminates the string that is read
with a null character.
• %ws format specification can be used for reading a specified
number of characters from the input string.
• scanf with %s or %ws can ready only strings without whitespaces.
• 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.
• Example:
char line[80];
scanf(“%[^n]”,line);
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6. Library functions
• There are various string handling functions define in
string.h some of them are:
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7. strlen()
• In C, strlen() function calculates the length of string.
• It takes only one argument, i.e, string name.
Syntax:
temp_variable = strlen(string_name);
• Function strlen() returns the value of type integer.
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8. strcpy()
• Function strcpy() copies the content of one string to the
content of another string.
• Syntax of strcpy()
strcpy(destination,source);
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9. strcat()
• concatenates(joins) two strings.
• resultant string is stored in the first string
specified in the argument.
Syntax of strcat()
strcat(first_string,second_string);
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10. strcmp()
• compares two string and returns value 0, if the two strings are
equal.
Syntax of strcmp()
temp_varaible=strcmp(string1,string2);
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12. strlwr()
• function converts all the uppercase characters in that string to
lowercase characters.
• The resultant from strlwr() is stored in the same string.
Syntax of strlwr():-
strlwr(string_name);
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13. strupr()
• function converts all the lowercase characters in that string to
uppercase characters.
• The resultant from strupr() is stored in the same string.
Syntax of strupr()
strupr(string_name);
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14. Structure in C
– Introduction to structure
• Definition
• declaration of structure, declaration of structure variables
• initialization,
• accessing members of structure
• Array of structures
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15. What is structure
• Structure is user defined data type which allows to combine
data items of different kinds
• Structures are used to represent a record
• For example to keep track of books in a library, following
attributes about each book has to maintained−
– Book ID (Data Type – Int)
– Title (Data Type – Char)
– Author (Data Type – Char)
– Publication (Data Type – Char)
– Price (Data Type – Float)
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