TOUPPER(3) (simplified)
NAME
toupper -- lower case to upper case letter conversion
SYNOPSIS
int toupper(int c);
DESCRIPTION
The toupper() function converts a lower-case letter to the corresponding upper-case letter. The argument must be representable as an unsigned char or the value of EOF.
RETURN VALUES
If the argument is a lower-case letter, the toupper() function returns the corresponding upper-casse letter if there is one; otherwise, the argument is returned unchanged.
Understandable explanation
I don't think I'll need to explain with more details what this function does, the man is pretty self-explanatory on this point.
Hints
ft_toupper.c
intft_toupper(int c){if (/* c is lower-case letter */)return (/* corresponding upper-case letter */);return (c);}
Commented solution
ft_toupper
ft_toupper.c
#include"libft.h"intft_toupper(int c){ /* this checks if the character is a lower-case letter * with the decimal ASCII values (97 => a; 122 => z) */if (c >=97&& c <=122) /* in the ASCII table, upper-case letter are indexed 32 * less than lower-case letter, so to get the corresponding * upper-case letter, we substract 32 to the lower-case * letter */return (c -32); /* As said in the man, if the character is not a lower-case * letter, the argument is returned unchanged, that's why we * return c directly */return (c);}