gistfile1.m

float screenResolution() {
	struct utsname systemInfo;
	uname(&systemInfo);
	char *name = systemInfo.machine;

	float ppi;
	if ((strstr(name, "iPod") != NULL) && (strstr(name, "iPod4") == NULL)) {
		// older ipod touches
		ppi = 163;
	} else if ((strstr(name, "iPhone") != NULL) && (strstr(name, "iPhone3") == NULL)) {
		// older non-retina iphones
		ppi = 163;
	} else if ((strstr(name, "iPad") != NULL) && (strstr(name, "iPad3") == NULL)) {
		// ipad 1, ipad 2
		ppi = 132;
	} else if (strstr(name, "iPad3") != NULL) {
		// ipad 3
		ppi = 264;
	} else {
		// iphone 4/4s, ipod touch 4g or simulator
		ppi = 326;
	}
	return ppi;
}