Expected } at the end of input
Your code is completely wrong in almost every respect.



#define char incomingByte; //Defines incomingByte 


That line means that the compiler will substitute incomingByte; whenever it sees char.



#define char sendBack = K;


Now it will substitute sendBack = K; when it sees char.



#define char ?;


Now it will substitute ?; when it sees char.



#define pollTime;


I don't know what you are thinking here. If you are trying to declare a variable you have to give a type, like this:

int pollTime;




bool running = true;

void setup() {
Serial.begin(9600); //Set data rate.
}
void loop() {


Those lines are OK.



for(Serial.available() &gt; 0;)  { //Gets you the number of bytes that are available to be read from the serial port.


You don't want the semicolon there. A for loop is not written like that. You possibly mean while, ie.

while(Serial.available() &gt; 0) 




pollTime = delayMicroseconds(200); // Sets a poll time of 200 microseconds.


That is doing nothing of the sort. It is delaying 200 µs, it isn't setting anything.



incomingByte  = Serial.read();


That line is OK, assuming you declared incomingByte like this, and not the way you did:

char incomingByte; 




if(incomingByte = ?) {


That needs to be in single quotes, as you are comparing a character. Also you compare with == not = ie.

if(incomingByte == '?') {




Serial.print(sendBack);


It looks from your earlier code you mean:

Serial.print('K');




  }
 }
}  


These lines look OK.



I suggest you read a beginners page about C programming. This is just pure guesswork what you are doing here. For one thing, read up on how #define works. Here is one page: https://www.techonthenet.com/c_language/constants/create_define.php. And another: http://www.cprogramming.com/reference/preprocessor/define.html