how to convert lowercase to upper case without using string.h?

[fmedina151]

how would I get this to work right now all its doing is giving every value an ascii of 222 capital I with an accent.

void Upcase (char S[ ])
{
  
	for(int i = 0; S[i]; ++i)
		if ((S[i]>='a') && (S[i]<='z'))
			S[i] = S[(i-32)];

[long double main]

Are you allowed to use this?
http://www.cplusplus.com/reference/cctype/toupper/

[booradley60]

By this:
S[i] = S[(i-32)];
I think you mean this:
S[i] = S[i] - 32;