QByteArray sum

[FalloutST]

AVR

for (int i = 1; i < sp_dataLength; i++) {
       sum += sp_recievedData[i];
   }

for (int i = 1; i < sp_dataLength; i++) {
       sum += sp_recievedData[i];
   }

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Qt

for (int i = 0; i < sp_dataLength; i++) {
       bytearray[0] = bytearray[0] + sp_ar_dataToSend[i];
    }

for (int i = 0; i < sp_dataLength; i++) {
       bytearray[0] = bytearray[0] + sp_ar_dataToSend[i];
    }

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output
sp_recievedData[i] : 1, 10, 215, 35, 60
result sum: 65
result bytearray[0] : 65

bytearray[0] - is QByteArray same as dataToSend

1+10+215+35+60 = 321 - 256 = 65

May I ask you?
If so: why should I count it in integer if it is loss prevention protocol?

My question is replacement bytearray[0] by other variable, in QT, to operate BYTE. CHAR crush....

I can't say it other "clear" way.