gistfile1.c

// declare a character array of 50 elements (0 to 49)
char buffer[50];
// declaring the index, it should be a number, but it works as char anyhow
char i;
 
// this is the setup function, simple commands that occur only once
void setup(){
  // let's start serialing with a baud rate of 9600 bytes per second
  Serial.begin(9600);
  // memory setting: all 50 elements of the char array are equal to null character
  memset(buffer, '\0', 50);
}

// this is the loop function, it's an infinite loop
void loop(){
  i = 0;
  // while we have serial data
  while (Serial.available()) {
    // store this char in the char array and then increment the index by 1
    buffer[i++] = Serial.read();
    // put a null character after storing 1 char, however, this gets override at the next iteration of the while loop
    buffer[i] = '\0';
  } // then repeat the process until we will not have any data. and the last item will be null character 
  // if the length of the buffer will be more than 0 elements, print the buffer. 
  if (strlen(buffer) > 0){
    Serial.println(buffer);
  }
} // repeat the loop