Get a string, make a copy of it, capitalize the copy.

malloc.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>

int main(void) {
    // define a string (or get from user input)
    char *s = "santosh";

    // copy that string into memory
    // otherwise it will just reference to it
    char *t = malloc((strlen(s) + 1) * sizeof(char));

    // the real copying goes here
    for (int i = 0, n = strlen(s); i <= n; i++) {
        t[i] = s[i];
    }
    
    // make the first char capital
    if (strlen(t) > 0) {
        t[0] = toupper(t[0]);
    }

    printf("s: %s\n", s);
    printf("t: %s\n", t);
    
    // to prevent memory leak
    free(t);
    return 0;
}