struct MyStruct {
  int valSum;
  int valSub;
  int valMul;
};

byte a, b;
int c;

int f, g;
int d;

MyStruct compute(int val1, int val2) {
  MyStruct str;
  str.valSum = val1 + val2;
  str.valSub = val1 - val2;
  str.valMul = val1 * val2;
  return str;
}

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  MyStruct str;
  str = compute(3, 4);
  Serial.println(str.valSum);
  Serial.println(str.valSub);
  Serial.println(str.valMul);

a = 10;
b = 20;
sumFunction();
Serial.println(c);
  // после вызова функции
  // с имеет значение 30

f = 20;
g = 40;
d = sumFunction2();
Serial.println(d);
Serial.println(sumFunction2());

//a = 50;
//b = 60;
c = sumFunction3(a, b);
Serial.println(c);

//MyStruct str2;
//MyStruct str2 = compute2(5, 6);
//Serial.println(ToString() str2);
//Serial.println(compute2(5, 6);
//Serial.println(compute2.valMul);

}

void loop() {
  // put your main code here, to run repeatedly:

}

void sumFunction() {
  c = a + b;
}

int sumFunction2() {
  return (f + g);
}

int sumFunction3(byte paramA, byte paramB) {
  return (paramA + paramB);
}

//MyStruct compute2(int val1, int val2) {
//  return (MyStruct) {val1 + val2, val1 - val2, val1 * val2};
//}