The asc code values of characters'1','2' and' 3' are 49, 50 and 5 1 respectively.

The computer runs printf("%c, ",b++); Statement,

The output format is %c character format.

So first output the character b, which is 2, and then add1to b;

At this time, b=3, and asc code value is 5 1.

Then run printf("%d\n ",b-a);

The output format is %d plastic format.

So the difference between the asc code value of B and the asc code value of A is output;

That is 51-49 = 2;

So the running result of the program is 2, 2.