DAC Controlled with Arduino

I am trying to control a resistor ladder DAC using an Arduino.
Basically, I am trying to control a group of 8 digital out pins based on a decimal
number that I input via the serial interface.

The issue that I am currently having is with

char command[4] = inData[];

How do I access this array?

I get an error of “expected primary-expression before ‘]’ token”

char inData[20]; // Allocate some space for the string
char inChar; // Where to store the character read
byte index = 0; // Index into array; where to store the character

void setup()
{
  Serial.begin(115200);
  for(byte i = 0; i < 8; i++){
    pinMode(-i+11,OUTPUT);
  }

}

void loop()
{
 if (Serial.available() ) {
      while(Serial.available() > 0)
   {
      char aChar = Serial.read();
      if(aChar == '\n')
      {
         // End of record detected. Time to parse

         index = 0;
         inData[index] = NULL;
      }
      else
      {
         inData[index] = aChar;
         index++;
         inData[index] = '\0'; // Keep the string NULL terminated
      }
   }
  int someValue = 100; //For this example, lets convert the number 20

  char binary[9] = {0}; //This is where the binary representation will be stored
  Serial.println(someValue); //print out our string.
  
 char command[4] = inData[]; //How do I access this array?
  
 someValue= atoi(&command[1]);
Serial.println(someValue); //Print value recieved from PC
  
  someValue += 208; //Adding 208 so that there will always be 8 digits in the string

  itoa(someValue,binary,2); //Convert someValue to a string using base 2 and save it in the array named binary
  char* string = binary + 1; //get rid of the most significant digit as you only want 8 bits
  Serial.println(); //Space

  Serial.println(string); //print out the string that will be applied to pins
  for(byte i = 0; i < 8; i++){
    digitalWrite(-i+11,string[i] - '0'); //write to the pin (the - '0' converts the bit of the string to HIGH or LOW)
  
  }
 }
}

You cannot copy arrays like that but why do you need to ?
You can access the inData array just like any other.

Analog_EE:

char command[4] = inData[];

Which element of the inData array do you want to access there?

for(byte i = 0; i < 8; i++){
    pinMode(-i+11,OUTPUT);

Is this from an obfuscated C website?

I'd recommend learning about shift operators for this sort of thing - you don't need an array of characters
to hold 8 bits, a byte variable is sufficient!

Also you might want to then go on to consider direct port manipulation if speed/performance is an issue,
it is possible to change upto 8 pins simultaneously (if they are in the same "port" on the chip) - however
that involves making the code hardware-specific.