Comparing senderNumber[20] to integer

Hardware Arduino GSM Shield
5

You are comparing two array of characters. If you want to compare two numbers mathematically, you should compare two integer variables, in other words, you should cast myCharNumber and senderNumber to integer with atoi function. If you want to compare two array for know if they are exactly equal (with letters and numbers), you should use strcmp(array1, array2).

Comparison of two numbers mathematically:

  char myCharNumber[20] = "+12223333";
  char senderNumber[20] = "+656543344";
  int myIntNumber = atoi(myCharNumber);
  int myIntSenderNumber = atoi(senderNumber);
  
  if(myIntSenderNumber < myIntNumber)
  {
    Serial.println("SenderNumber is less than myCharNumber");
  }
  else
  {
    Serial.println("SenderNumber is greater than myCharNumber");
  }

Comparison of two arrays (character by character):

  Serial.begin(9600);
  char myCharNumber[20] = "+656543344";
  char senderNumber[20] = "+656543344";

  if(strcmp(senderNumber, myCharNumber) == 0)
  {
    Serial.println("Equal");
  }
  else
  {
    Serial.println("Not equal");
  }