ARDUINO UNO- Need explains about program - arduino

Question

I am begginer on Arduino. I am student and this is my first homework.
Please, could someone explain to me how to understand the following codes. Which code is better? How do operators affect the executive speed? Below is the content.
"The task was to measure the speed of code execution depending on the programming technique used. The program code was designed to expose the high and low states to the D10 (PB2) port respectively without entering delays – as a result, we obtained a rectangular waveform with the maximum frequency for a given program recording method. Programs were written by putting all statements in void setup() omitting the void loop().
Preparation for the exercise consisted in connecting the Arduino Uno board to the USB port, starting the Arduino IDE environment and turning on the oscilloscope. The oscilloscope was used to observe the rectangular waveform generated from the D10 pin (PB2) and to measure its frequency."
Code of the first program:
const byte outPin = 10;
void setup() {
pinMode(outPin,OUTPUT);
while (1)
{
digitalWrite(outPin, HIGH);
digitalWrite(outPin, LOW);
}
Code of the second program:
const byte outPin = B00000100;
void setup() {
DDRB | = outPin;
while (1)
{
PORTB = B00000100;
PORTB = B11111011;
}
Third program code:
const byte outPin =10;
byte state =0;
void setup() {
pinMode(outPin,OUTPUT);
while (1)
{
digitalWrite(outPin, state);
state = !state;
}
Code of the fourth program:
#define _BV(n) (1<<n)
const byte outPin= B00000100;
byte state = _BV(2);
void setup()
{
DDRB|=outPin;
}
while (1){
PORTB |=state;
PORTB &=~state;
}
Code of the fifth program:
const byte outPin= B00000100;
void setup()
{
DDRB|=outPin;
while (1){
PORTB |=B00000100;
PORTB &=B11111011;}
}
As I said I am begginer on ARDUINO UNO. I cannot find any solution to explain exactly my homework.

Answer 1

Which code is better?
The first one, of course. Reasons:
Usually, it's fast enough.
The other ones are hardware specific and do not run on any Arduino, but just on atmega328P microcontrollers.
How do operators affect the executive speed?
It's the call to digitalWrite, which makes the difference, not some operators like ~ . You should look for an similarly hardware independent replacement to digitalWrite, which does the translation between Arduino pin number and hardware register only once at compile time.
BTW: your question is off topic here :)