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The definition of C string , how to declare a string, string definition in C and what is string in C language are all covered in this article. With examples, it goes over the many ways to initialize strings. It discusses how to read text from a user and how to read text with whitespace. Also addressed is how to represent strings as pointers and send them to functions. It covers what we learned in the article by going over an example of a C String. Finally, it compares and contrasts character arrays and string literals.<\/p>\n
Strings are useful for communicating information from the program to the program user and, thus, are a part of all programming languages and applications. They are implemented with character arrays that behave like usual arrays with which we can perform regular operations, including modification. Another way of implementing strings is through pointers since character arrays act as pointers. These pointers point to string literals and cannot be modified as string literals are stored in the read-only memory by most compilers. Thus, any attempt at modifying them leads to undefined behavior.<\/p>\n
A string is a group of characters, such as letters, numbers, symbols, and punctuation marks, that are arranged in a linear fashion. A string in C is a group of characters that is finished with the NULL character "0." For instance:<\/p>\n
char str[] = \"PrepBytes.\\0\";<\/code><\/pre>\nLike many other programming languages, C encloses strings in double quotes ("") while enclosing characters in single quotes (”). A null character (\\0) is automatically added at the conclusion when the compiler discovers a string of characters contained in double quotation marks.<\/p>\n
So, the string is stored in this way:<\/p>\n
![\"\"](\"https:\/\/prepbytes-misc-images.s3.ap-south-1.amazonaws.com\/assets\/1673871045017-string%20in%20c1.png\")
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A group of zero or more multibyte characters surrounded in double quotes, such as "abc," is referred to as a string literal. String literals cannot be changed (and are placed in read-only memory). Any attempt to change their values leads to behavior that is undefined.<\/p>\n
How to Declare String in C<\/h3>\n
A character-based array known as a String in the C programming language. In contrast to other programming languages like C++, C does not natively provide the string data type. Therefore, in order to show a string in C, character arrays are required. Declaring a string in C generally looks like this:<\/p>\n
char variable[array_size];<\/code><\/pre>\nConsequently, the traditional declaration can be expressed as follows::<\/p>\n
char str[5];\nchar str2[50];<\/code><\/pre>\nWe must always take into consideration the extra space that the null letter (\\0) occupies.<\/p>\n
Highlights<\/strong>
\nIn C, strings are declared using character arrays.
\nTheir general syntax is as follows:<\/p>\nchar variable[array_size];<\/code><\/pre>\nInitializing C String<\/h3>\n
There are four methods of initializing a string in C:<\/p>\n
1. Assigning a string literal with size<\/strong>
\nDirectly assigning a string literal to a character array is possible as long as the array size is at least one greater than the string literal original length.<\/p>\nNote:<\/strong> The null character requires one additional space, therefore we must always take it into consideration when calculating the initial size. Setting the initial size to be n+1 will allow us to store a string of size n.
\nFor example:<\/strong><\/p>\nchar str[8] = \"PrepBytes.\";<\/code><\/pre>\nAlthough this string should be 10 characters long, we kept the size at 11 to include the Null character. The Null character (\\0) is automatically added at the end by the compiler.<\/p>\n
Note:<\/strong> If the string is too long for the array, it only accepts characters based on available space. For instance:<\/p>\nchar str[3] = \"PREPBYTES.\";\nprintf(\"%s\",str);<\/code><\/pre>\nOutput<\/strong><\/p>\nPRE<\/code><\/pre>\n2. Assigning a string literal without size<\/strong>
\nAnother option is to simply assign a string literal with no size to a character array. At compile time, the compiler automatically calculates the size.<\/p>\nchar str[] = \"PREPBYTES\";<\/code><\/pre>\nThe important thing to keep in mind is that because this string is an array and is called "str," it functions as a pointer.<\/p>\n
3. Assigning character by character with size<\/strong>
\nA string can also be assigned character per character. But it’s crucial to set the final character to be ‘0’. For instance:<\/p>\nchar str[11] = {'P', 'R', 'E', 'P', 'B', 'Y', \u2018T\u2019, \u2018E\u2019, \u2018S\u2019, '.','\\0'};<\/code><\/pre>\n4. Assigning character by character without size<\/strong>
\nWe also assign character by character with the Null Character at the end, similar to assigning straight without regard to size. The length of the string will be determined automatically by the compiler.<\/p>\nchar str[] = {{'P', 'R', 'E', 'P', 'B', 'Y', \u2018T\u2019, \u2018E\u2019, \u2018S\u2019, '.','\\0'};<\/code><\/pre>\n![\"\"](\"https:\/\/prepbytes-misc-images.s3.ap-south-1.amazonaws.com\/assets\/1673871045017-string%20in%20c2.png\")
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Highlights:<\/strong> There are four methods of initializing a string in C:
\n1. Assigning a string literal with size.<\/strong>
\n2. Assigning a string literal without size.<\/strong>
\n3. Assigning character by character with size.<\/strong>
\n4. Assigning character by character without size.<\/strong><\/p>\nAssign Value to Strings<\/h3>\n
Once they have been declared, character arrays cannot be given a string literal using the ‘=’ operator.<\/p>\n
char str[100];\nstr = \"String.\";<\/code><\/pre>\nSince assignment operations are not supported after strings are declared, this will result in a compilation error. We can utilize the following two techniques to overcome this:<\/p>\n
\n- While initializing it, as described above, assign the value to a character array.<\/li>\n
- \n
The value we want to add to the character array can be copied using the strcpy() function. The following is the strcpy() syntax:
\nstrcpy(char destination, const char<\/em> source);
\nThe string pointed by the source is copied to the destination, along with the null character. For instance:<\/p>\nchar str[20];
\nstrcpy(str,"Strings.");
\nThis gives the string its assigned value.<\/p>\n<\/li>\n<\/ol>\n
Note –<\/strong> Making sure the value assigned has a length that is less than or equal to the character array’s maximum size.<\/p>\nHighlights:<\/strong><\/p>\n\n- Once they have been declared, character arrays cannot be given a string literal using the ‘=’ operator.<\/li>\n
- Both initialization time and the strcpy() function can be used for assignment.<\/li>\n<\/ol>\n
Read String from the User<\/h3>\n
Scanf(), the most popular method for reading strings, reads a string of characters until it runs into whitespace (i.e., space, newline, tab, etc.). The process of accepting input with whitespace is described in the section that follows. For instance,<\/p>\n
char str[25];\nscanf(\"%s\", str);<\/code><\/pre>\nIf we enter the following input:<\/p>\n
PrepBytes is amazing.<\/code><\/pre>\nWe obtain the following Output:<\/p>\n
PrepBytes<\/code><\/pre>\nAs we can see, once it detects whitespace, scanf() stops accepting input.<\/p>\n
Note –<\/strong><\/p>\n\n- In C, %s is the format specifier that is used to input and output strings.<\/li>\n
- You may have noticed that the variable’s name is typically prefixed by a & operator when using scanf(). This is not the case in this instance since the character array’s character pointer points to the address of the array’s first character. Therefore, there is no need to employ the address operator(&).
\nHighlights:<\/strong> In C, scanf() can be used to read strings. But it only reads till it hits a whitespace.<\/li>\n<\/ol>\nHow to Read a Line of Text?<\/h3>\n
As it automatically stops reading when it encounters whitespace, the scanf() operation cannot read strings that contain spaces. By combining fgets() with puts(), we can read and print strings with whitespace:<\/p>\n
\n- fgets()<\/strong> An array of characters can be read using the fgets() method. Its statement is as follows:
\nfgets(name_of_string, number_of_characters, stdin);
\n*name_of_string<\/em>: It is the variable where the string will be kept. <\/strong>number_of_characters: You should read the string’s maximum length. <\/strong>stdin:** The string needs to be read from the filehandle in this case.<\/li>\n- puts():<\/strong> The function puts() makes it easy to show strings.
\nputs(name_of_string);<\/li>\n<\/ul>\nname_of_string:<\/strong> It is the variable that will hold the string.<\/p>\nUsing both functions as an example:
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