Guide to tolower() Function in C with Examples
Enhance your C programming skills with our detailed guide on how to use toupper() function in C effectively.
In this tutorial, we will discuss the tolower() C function for converting uppercase C strings into lowercase.
Introduction to tolower() Function in C
The tolower() function is a standard library function in the C programming language that converts a given character to its lowercase equivalent.
The tolower() function is part of the ctype.h header file in C, which provides a collection of functions for character handling. It is commonly for string manipulation and text processing when it comes to C programming, particularly when dealing with user input, where case sensitivity can be an issue.
Here is the syntax for the tolower() function:
int tolower(int c);
The function takes a single argument c, an integer representing the character to convert. If the argument is an uppercase letter, tolower() returns the corresponding lowercase letter. And when the argument is already a lowercase letter, it returns unchanged. Or, if the argument is not a letter, the function returns the argument as it is.
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C Examples of tolower() Function
Example 1: Converting a single character to lowercase
#include <stdio.h>#include <ctype.h>
int main() { char c = 'A'; char lc = tolower(c); printf("The lowercase of %c is %c\n", c, lc); return 0;}
Output
The lowercase of A is a
In this example, the tolower() function converts the uppercase character ‘A’ to its lowercase equivalent. The variable c is first initialized with the uppercase character ‘A’, and then passed as an argument to the tolower() function. The resulting lowercase character is stored in the lc variable, and then printed on the screen.
Example 2: Converting a string to lowercase
#include <stdio.h>#include <ctype.h>#include <string.h>
int main() { char str[] = "HELLO WORLD"; int len = strlen(str); for (int i = 0; i < len; i++) { str[i] = tolower(str[i]); } printf("The lowercase of the string is %s\n", str); return 0;}
Output
The lowercase of the string is hello world
In this example, the tolower() function converts each uppercase character in a given string to its lowercase equivalent. The str variable is first initialized with the string “HELLO WORLD”, and then each character in the string is passed as an argument to the tolower() function using a for loop. The resulting lowercase character then prints to the screen using the printf() function.
Example 3: Converting user input to lowercase
#include <stdio.h>#include <ctype.h>
int main() { char input[100]; printf("Enter a string: "); fgets(input, 100, stdin); // read user input // convert the string to lowercase for(int i = 0; input[i]; i++){ input[i] = tolower(input[i]); } printf("The lowercase string is: %s", input); return 0;}
Output:
Enter a string: Tyre
The lowercase string is: tyre
In this code, the user is prompted to enter a string. The fgets() function reads the input from the user, and the tolower() function is in a loop to convert each input string character to lowercase. The converted string is then printed to the console using printf().
Note that the tolower() function only works with characters, so you need to loop through each character of the string and apply the function to each character individually in order to convert the entire string to lowercase.
Example 4: Comparing characters case-insensitively
#include <stdio.h>#include <ctype.h>
int main() { char ch1 = 'X'; char ch2 = 'x';
if (tolower(ch1) == tolower(ch2)) { printf("The characters are equal (case-insensitive).\n"); } else { printf("The characters are not equal (case-insensitive).\n"); } return 0;}
Output:
In this example, the tolower() function converts ch1 and ch2 to lowercase before comparing them. This allows us to compare the characters case-insensitively, since the uppercase and lowercase versions of the same letter are treated as equal. The if statement tests whether the two characters are equal (case-insensitive), and prints the appropriate message to the screen.
Example 5: Converting characters in an array to lowercase
#include <stdio.h>#include <ctype.h>
int main() { char characters[] = {'A', 'b', 'C', 'd', 'E', 'f'}; int length = sizeof(characters) / sizeof(char); // calculate the length of the array // convert each character to lowercase for(int i = 0; i < length; i++) { characters[i] = tolower(characters[i]); } // print the lowercase characters for(int i = 0; i < length; i++) { printf("%c ", characters[i]); } return 0;}
Output:
a b c d e f
In this code, an array of characters is defined, and the length of the array is calculated using the sizeof() operator. The tolower() function is in a loop to convert each character in the array to lowercase. The converted characters are then printed to the console using printf().
Endnotes
In conclusion, the function tolower() is a useful and uncomplicated resource that can enhance the efficiency and effectiveness of C programming. This article outlines the fundamentals of tolower() and gives various instances of how you can apply in C programs. To learn more, check out C programming courses.
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