>>Look up strstr and strchr.
That's not in stdio.h, they're in string.h.
>> how could you do this without using anything but stdio.h?
Use sscanf, since it only reads up to the next whitespace you can break up words easily. The biggest problem is how to move the get pointer forward through the string using it as a loop. This can be done by using the %n format for sscanf that tells you how many characters were read, just assign a pointer to the array and after each repetition of the loop, add the value of %n to the pointer until there's nothing left.
Code:
#include <stdio.h>
int main(void)
{
int n;
char name[] = "My name is Bob", *namep = name;
char word[5];
while (sscanf(namep, "%s%n", word, &n) == 1)
{
word[0] = 'A';
printf("%s\n", word);
namep += n;
}
return 0;
}