isalpha() in C
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Overview
isalpha() is a function used to check whether the input character is an alphabet or not. It is present in the ctype header file in the C standard library.
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Syntax of isalpha() in C
The syntax of isalpha is:
Parameters of isalpha() in C
The isalpha() function takes the following parameter as an input.
- c: a character or its ASCII value
Return Values of isalpha() in C
Return Type: int
The function returns different values depending on the input. They are as follows.
- If the character is an alphabet(lowercase or uppercase), it returns a non-zero number.
- If the character is not an alphabet, it returns zero.
Example of isalpha() in C
Output
What is isalpha() in C?
The isalpha() function in C is used to check whether a character is an alphabet or not. It is defined in the ctype header file in the C Standard Library.
It returns a non-zero number if it is an alphabet('a'-'z' and 'A'-'Z'). Else it returns zero for all other characters.
Note: To check whether the given character is an alphabet, the function converts the character into its ASCII value.
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Let's see some more examples to understand how this function works.
Example 1: Program to use isalpha() function for lowercase alphabets
Output
Explanation In the above program, a lowercase alphabet(a) is passed to the function isalpha(). It returns a non-zero number(1024). Hence, the character passed is an alphabet.
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Example 2: Program to use isalpha() function for uppercase alphabets
Output
Explanation In the above program, a uppercase alphabet(Q) is passed to the function isalpha. It returns a non-zero number(1024). Hence, the character passed is an alphabet.
Example 3: Program to use isalpha() function for numbers
Output
Explanation In the above program, a digit(9) is passed to the function isalpha. It returns zero. Hence, the character passed is not an alphabet.
Example 4: Program to use isalpha() function for special characters
Output
Explanation In the above program, a special character(*) is passed to the function isalpha. It returns zero. Hence, the character passed is not an alphabet.
Example 5: Program to use isalpha() function by passing ASCII values of characters.
Output
Explanation In this example, we pass the ASCII value of 'm'(ASCII value = 109) and '-'(ASCII value = 45) to the function. It returns the expected output.
Conclusion
- The isalpha() function is defined in the ctype header file in the C standard library.
- It is used to check whether a character is an alphabet or not.
- It returns a non-zero if the character is an alphabet and zero otherwise.
