sizeof of a const that uses PROGMEM

If I have an array defined

const unsigned int lookup[] PROGMEM = {
	0x0000,0xc0c1,0xc181,0x0140,0xc301,0x03c0,0x0280,0xc241,0xc601,0x06c0,0x0780,
	0xc741,0x0500,0xc5c1,0xc481,0x0440,0xcc01,0x0cc0,0x0d80,0xcd41,0x0f00,0xcfc1,
	0xce81,0x0e40,0x0a00,0xcac1,0xcb81,0x0b40,0xc901,0x09c0,0x0880,0xc841,0xd801,
	0x18c0,0x1980,0xd941,0x1b00,0xdbc1,0xda81,0x1a40,0x1e00,0xdec1,0xdf81,0x1f40,
	0xdd01,0x1dc0,0x1c80,0xdc41,0x1400,0xd4c1,0xd581,0x1540,0xd701,0x17c0,0x1680,
	0xd641,0xd201,0x12c0,0x1380,0xd341,0x1100,0xd1c1,0xd081,0x1040,0xf001,0x30c0,
	0x3180,0xf141,0x3300,0xf3c1,0xf281,0x3240,0x3600,0xf6c1,0xf781,0x3740,0xf501,
	0x35c0,0x3480,0xf441,0x3c00,0xfcc1,0xfd81,0x3d40,0xff01,0x3fc0,0x3e80,0xfe41,
	0xfa01,0x3ac0,0x3b80,0xfb41,0x3900,0xf9c1,0xf881,0x3840,0x2800,0xe8c1,0xe981,
	0x2940,0xeb01,0x2bc0,0x2a80,0xea41,0xee01,0x2ec0,0x2f80,0xef41,0x2d00,0xedc1,
	0xec81,0x2c40,0xe401,0x24c0,0x2580,0xe541,0x2700,0xe7c1,0xe681,0x2640,0x2200,
	0xe2c1,0xe381,0x2340,0xe101,0x21c0,0x2080,0xe041,0xa001,0x60c0,0x6180,0xa141,
	0x6300,0xa3c1,0xa281,0x6240,0x6600,0xa6c1,0xa781,0x6740,0xa501,0x65c0,0x6480,
	0xa441,0x6c00,0xacc1,0xad81,0x6d40,0xaf01,0x6fc0,0x6e80,0xae41,0xaa01,0x6ac0,
	0x6b80,0xab41,0x6900,0xa9c1,0xa881,0x6840,0x7800,0xb8c1,0xb981,0x7940,0xbb01,
	0x7bc0,0x7a80,0xba41,0xbe01,0x7ec0,0x7f80,0xbf41,0x7d00,0xbdc1,0xbc81,0x7c40,
	0xb401,0x74c0,0x7580,0xb541,0x7700,0xb7c1,0xb681,0x7640,0x7200,0xb2c1,0xb381,
	0x7340,0xb101,0x71c0,0x7080,0xb041,0x5000,0x90c1,0x9181,0x5140,0x9301,0x53c0,
	0x5280,0x9241,0x9601,0x56c0,0x5780,0x9741,0x5500,0x95c1,0x9481,0x5440,0x9c01,
	0x5cc0,0x5d80,0x9d41,0x5f00,0x9fc1,0x9e81,0x5e40,0x5a00,0x9ac1,0x9b81,0x5b40,
	0x9901,0x59c0,0x5880,0x9841,0x8801,0x48c0,0x4980,0x8941,0x4b00,0x8bc1,0x8a81,
	0x4a40,0x4e00,0x8ec1,0x8f81,0x4f40,0x8d01,0x4dc0,0x4c80,0x8c41,0x4400,0x84c1,
	0x8581,0x4540,0x8701,0x47c0,0x4680,0x8641,0x8201,0x42c0,0x4380,0x8341,0x4100,
	0x81c1,0x8081,0x4040 };

Does the following line return the number of elements of the array?

(sizeof(lookup) / sizeof(int))

If not what will return the number of element of array lookup?

Yes, although its would be better to use information the compiler already knows about the array.

#define NUM_ENTRIES(ARRAY) (sizeof(ARRAY) / sizeof(ARRAY[0]))

size_t   countEntries = NUM_ENTRIES(lookup);

It's more generic if you use:

#define ELEMENTS(x) (sizeof(x) / sizeof(x[0]))

void setup() {
  // put your setup code here, to run once:

const unsigned int lookup[] PROGMEM = {
  0x0000,0xc0c1,0xc181,0x0140,0xc301,0x03c0,0x0280,0xc241,0xc601,0x06c0,0x0780,
  0xc741,0x0500,0xc5c1,0xc481,0x0440,0xcc01,0x0cc0,0x0d80,0xcd41,0x0f00,0xcfc1,
  0xce81,0x0e40,0x0a00,0xcac1,0xcb81,0x0b40,0xc901,0x09c0,0x0880,0xc841,0xd801,
  0x18c0,0x1980,0xd941,0x1b00,0xdbc1,0xda81,0x1a40,0x1e00,0xdec1,0xdf81,0x1f40,
  0xdd01,0x1dc0,0x1c80,0xdc41,0x1400,0xd4c1,0xd581,0x1540,0xd701,0x17c0,0x1680,
  0xd641,0xd201,0x12c0,0x1380,0xd341,0x1100,0xd1c1,0xd081,0x1040,0xf001,0x30c0,
  0x3180,0xf141,0x3300,0xf3c1,0xf281,0x3240,0x3600,0xf6c1,0xf781,0x3740,0xf501,
  0x35c0,0x3480,0xf441,0x3c00,0xfcc1,0xfd81,0x3d40,0xff01,0x3fc0,0x3e80,0xfe41,
  0xfa01,0x3ac0,0x3b80,0xfb41,0x3900,0xf9c1,0xf881,0x3840,0x2800,0xe8c1,0xe981,
  0x2940,0xeb01,0x2bc0,0x2a80,0xea41,0xee01,0x2ec0,0x2f80,0xef41,0x2d00,0xedc1,
  0xec81,0x2c40,0xe401,0x24c0,0x2580,0xe541,0x2700,0xe7c1,0xe681,0x2640,0x2200,
  0xe2c1,0xe381,0x2340,0xe101,0x21c0,0x2080,0xe041,0xa001,0x60c0,0x6180,0xa141,
  0x6300,0xa3c1,0xa281,0x6240,0x6600,0xa6c1,0xa781,0x6740,0xa501,0x65c0,0x6480,
  0xa441,0x6c00,0xacc1,0xad81,0x6d40,0xaf01,0x6fc0,0x6e80,0xae41,0xaa01,0x6ac0,
  0x6b80,0xab41,0x6900,0xa9c1,0xa881,0x6840,0x7800,0xb8c1,0xb981,0x7940,0xbb01,
  0x7bc0,0x7a80,0xba41,0xbe01,0x7ec0,0x7f80,0xbf41,0x7d00,0xbdc1,0xbc81,0x7c40,
  0xb401,0x74c0,0x7580,0xb541,0x7700,0xb7c1,0xb681,0x7640,0x7200,0xb2c1,0xb381,
  0x7340,0xb101,0x71c0,0x7080,0xb041,0x5000,0x90c1,0x9181,0x5140,0x9301,0x53c0,
  0x5280,0x9241,0x9601,0x56c0,0x5780,0x9741,0x5500,0x95c1,0x9481,0x5440,0x9c01,
  0x5cc0,0x5d80,0x9d41,0x5f00,0x9fc1,0x9e81,0x5e40,0x5a00,0x9ac1,0x9b81,0x5b40,
  0x9901,0x59c0,0x5880,0x9841,0x8801,0x48c0,0x4980,0x8941,0x4b00,0x8bc1,0x8a81,
  0x4a40,0x4e00,0x8ec1,0x8f81,0x4f40,0x8d01,0x4dc0,0x4c80,0x8c41,0x4400,0x84c1,
  0x8581,0x4540,0x8701,0x47c0,0x4680,0x8641,0x8201,0x42c0,0x4380,0x8341,0x4100,
  0x81c1,0x8081,0x4040 };

  Serial.begin(9600);
  Serial.print("The array has ");
  Serial.print(ELEMENTS(lookup));
  Serial.println(" in it.");
}

void loop() {
  // put your main code here, to run repeatedly:
}

Edit: lloyddean: You're too quick for me...

Thank you.

Now my next problem. Using the same constant array "lookup" from above, I added code to my program

#include <avr/pgmspace.h>

const unsigned int lookup[] PROGMEM = {
	0x0000,0xc0c1,0xc181,0x0140,0xc301,0x03c0,0x0280,0xc241,0xc601,0x06c0,0x0780,
	0xc741,0x0500,0xc5c1,0xc481,0x0440,0xcc01,0x0cc0,0x0d80,0xcd41,0x0f00,0xcfc1,
	0xce81,0x0e40,0x0a00,0xcac1,0xcb81,0x0b40,0xc901,0x09c0,0x0880,0xc841,0xd801,
	0x18c0,0x1980,0xd941,0x1b00,0xdbc1,0xda81,0x1a40,0x1e00,0xdec1,0xdf81,0x1f40,
	0xdd01,0x1dc0,0x1c80,0xdc41,0x1400,0xd4c1,0xd581,0x1540,0xd701,0x17c0,0x1680,
	0xd641,0xd201,0x12c0,0x1380,0xd341,0x1100,0xd1c1,0xd081,0x1040,0xf001,0x30c0,
	0x3180,0xf141,0x3300,0xf3c1,0xf281,0x3240,0x3600,0xf6c1,0xf781,0x3740,0xf501,
	0x35c0,0x3480,0xf441,0x3c00,0xfcc1,0xfd81,0x3d40,0xff01,0x3fc0,0x3e80,0xfe41,
	0xfa01,0x3ac0,0x3b80,0xfb41,0x3900,0xf9c1,0xf881,0x3840,0x2800,0xe8c1,0xe981,
	0x2940,0xeb01,0x2bc0,0x2a80,0xea41,0xee01,0x2ec0,0x2f80,0xef41,0x2d00,0xedc1,
	0xec81,0x2c40,0xe401,0x24c0,0x2580,0xe541,0x2700,0xe7c1,0xe681,0x2640,0x2200,
	0xe2c1,0xe381,0x2340,0xe101,0x21c0,0x2080,0xe041,0xa001,0x60c0,0x6180,0xa141,
	0x6300,0xa3c1,0xa281,0x6240,0x6600,0xa6c1,0xa781,0x6740,0xa501,0x65c0,0x6480,
	0xa441,0x6c00,0xacc1,0xad81,0x6d40,0xaf01,0x6fc0,0x6e80,0xae41,0xaa01,0x6ac0,
	0x6b80,0xab41,0x6900,0xa9c1,0xa881,0x6840,0x7800,0xb8c1,0xb981,0x7940,0xbb01,
	0x7bc0,0x7a80,0xba41,0xbe01,0x7ec0,0x7f80,0xbf41,0x7d00,0xbdc1,0xbc81,0x7c40,
	0xb401,0x74c0,0x7580,0xb541,0x7700,0xb7c1,0xb681,0x7640,0x7200,0xb2c1,0xb381,
	0x7340,0xb101,0x71c0,0x7080,0xb041,0x5000,0x90c1,0x9181,0x5140,0x9301,0x53c0,
	0x5280,0x9241,0x9601,0x56c0,0x5780,0x9741,0x5500,0x95c1,0x9481,0x5440,0x9c01,
	0x5cc0,0x5d80,0x9d41,0x5f00,0x9fc1,0x9e81,0x5e40,0x5a00,0x9ac1,0x9b81,0x5b40,
	0x9901,0x59c0,0x5880,0x9841,0x8801,0x48c0,0x4980,0x8941,0x4b00,0x8bc1,0x8a81,
	0x4a40,0x4e00,0x8ec1,0x8f81,0x4f40,0x8d01,0x4dc0,0x4c80,0x8c41,0x4400,0x84c1,
	0x8581,0x4540,0x8701,0x47c0,0x4680,0x8641,0x8201,0x42c0,0x4380,0x8341,0x4100,
	0x81c1,0x8081,0x4040 };

int Result = 0;

void setup()
{

    for (int idx = 0; idx < 5; idx++)
    {
        Result = Result ^ pgm_read_word_near(lookup + idx);
    }
}

I get a precompile error for "pgm_read_word_near(loopup + idx);"
(I'm using Visual Studio 2015 for my IDE)

"expected an expression"

I looked at all of the examples and it looks like I'm doing what the example is doing.
Could anyone tell me what is wrong?

After adding the required routine 'loop' it compiles here just fine!

It looks like Visual Studios is complaining, but mine compiles also.
Must be a bug in the interpreter in VS15.