strlwr() function in C Last Updated : 04 Oct, 2018 Summarize Comments Improve Suggest changes Share Like Article Like Report The strlwr( ) function is a built-in function in C and is used to convert a given string into lowercase. Syntax: char *strlwr(char *str); Parameter: str: This represents the given string which we want to convert into lowercase. Returns: It returns the modified string obtained after converting the characters of the given string str to lowercase. Note: This is a non-standard function that works only with older versions of Microsoft C. Below programs illustrate the strlwr() function in C: Example 1:- C // C program to demonstrate // example of strlwr() function #include<stdio.h> #include<string.h> int main() { char str[ ] = "GEEKSFORGEEKS IS THE BEST"; // converting the given string into lowercase. printf("%s\n",strlwr (str)); return 0; } Output: geeksforgeeks is the best Example 2:- c // C program to demonstrate // example of strlwr() function. #include<stdio.h> #include <string.h> int main() { char str[] = "CompuTer ScienCe PoRTAl fOr geeKS"; printf("Given string is: %s\n",str); printf("\nString after converting to the " "lowercase is: %s",strlwr(str)); return 0; } Output: Given string is: CompuTer ScienCe PoRTAl fOr geeKS String after converting to the lowercase is: computer science portal for geeks Comment More infoAdvertise with us Next Article strol() function in C++ B bansal_rtk_ Follow Improve Article Tags : Misc C Language C-String C-Functions C-Library +1 More Practice Tags : Misc Similar Reads strol() function in C++ The strtol() function in C++ interprets the contents of a string as an integral number of the specified base and return its value as a long int.This function also sets an end pointer that points to the first character after the last valid numeric character of the string, if there is no such characte 3 min read strlen() function in c The strlen() function in C calculates the length of a given string. The strlen() function is defined in string.h header file. It doesn't count the null character '\0'. Syntax of C strlen() The syntax of strlen() function in C is as follows: size_t strlen(const char* str);Parameters The strlen() func 1 min read strrev() function in C The strrev() function is a built-in function in C and is defined in string.h header file. The strrev() function is used to reverse the given string. Syntax:char *strrev(char *str);Parameter:str: The given string which is needed to be reversed.Returns: This function doesn't return anything but the re 2 min read strupr() function in c The strupr( ) function is used to converts a given string to uppercase. Syntax: char *strupr(char *str); Parameter: str: This represents the given string which we want to convert into uppercase. Returns: It returns the modified string obtained after converting the characters of the given string str 1 min read iswlower() Function in C The iswlower() is a built-in function in C that checks whether the given wide character is a lowercase character or not. iswlower() function is defined inside the <wctype.h> in C. Syntax of iswlower() functionint iswlower(wint_t ch) Here, wint_t is a wide integer type used to represent a wide 4 min read strspn() function in C The strspn() function returns the length of the initial substring of the string pointed to by str1 that is made up of only those character contained in the string pointed to by str2. Syntax : size_t strspn(const char *str1, const char *str2) str1 : string to be scanned. str2 : string containing the 1 min read Like