gave up solving this /explain:

[Reem Alnuaimi]

int x,value;
int a=0,b=0,c=0,d=0;

for(x=10240953;x!=0;x=x/10){
value=x%10;

switch(value)
{
case2:case4:case6:case8:
a++;
break;
case3:case5:
b++;
case9:case7:
c++;
break;
default:
d++;
break;
}
}
cout<<"a"<<a<<"b"<<b<<"c"<<c<<"d"<<d;

Ans :
a=2 b=2 c=3 d=3

[salem c]

Does it help if you realise there is no break statement after b++?

[whitenite1]

@Reem Alnuaimi

There should be a space between the word case and the numbers.
IE: case 2: case 4:
etc.

[dhayden]

Here is the code with spaces after the cases, indented to reflect the block structure, and with the code needed to make it a program:

#include <iostream>
using namespace std;

int
main()
{
    int x, value;
    int a = 0, b = 0, c = 0, d = 0;

    for (x = 10240953; x != 0; x = x / 10) {
	value = x % 10;

	switch (value) {
	case 2:
	case 4:
	case 6:
	case 8:
	    a++;
	    break;
	case 3:
	case 5:
	    b++;
	case 9:
	case 7:
	    c++;
	    break;
	default:
	    d++;
	    break;
	}
    }
    cout << "a" << a << "b" << b << "c" << c << "d" << d;
}

The first thing to do is recognize that the loop on lines 10 & 11 causes value to take on the value of each digit in 10240953, in reverse order. So it's 3, then 5, then 9, 0, 4, 2, 0, and finally 1.

Next write the letters a,b,c,d on a sheet of paper, one per line:

a
b
c
d

Now simply examine the switch statement for each of those digits values and put a check mark next to a letter each time it's variable gets incremented.

For example, the first time through the loop, value=3. Control transfers to line 22 where b gets incremented. Then it falls through to line 25 and increments a. Then it breaks out of the switch statement. So your paper now looks like this:

a  |
b  |
c
d

Continue the same way with the rest of the digits. When you're done, your sheet will show how many times each variable got incremented. Easy peasy.

[keskiverto]

A compiler gives many warnings about the original code that are similar to:

warning: label 'case2' defined but not used [-Wunused-label]

That is a hint to focus attention to the labels.

The syntax of labels: https://en.cppreference.com/w/cpp/language/statements#Labels

[lastchance]

#include <iostream>
using namespace std;

int main()
{
    int x, value;
    int a = 0, b = 0, c = 0, d = 0;

    for ( x = 10240953; x != 0; x = x / 10 )
    {
       value = x % 10;
       cout << "\nvalue is " << value << '\n';
	   switch (value)
	   {
	      case 2:
	      case 4:
	      case 6:
	      case 8:
	         a++;   cout << "a\n";
	         break;
	         
	      case 3:
	      case 5:
	         b++;   cout << "b (and falling through)\n";
	      case 9:
	      case 7:
	         c++;   cout << "c\n";
	         break;
	         
	      default:
	         d++;   cout << "d\n";
	         break;
	   }
    }
    cout << "\n\na: " << a << "    b: " << b << "    c: " << c << "    d: " << d;
}

value is 3
b (and falling through)
c

value is 5
b (and falling through)
c

value is 9
c

value is 0
d

value is 4
a

value is 2
a

value is 0
d

value is 1
d


a: 2    b: 2    c: 3    d: 3 

[Reem Alnuaimi]

@dhayden : your comment was so helpful very detailed and accurate , I am so thankful to you .

you too @lastchance thanks so much was straightforward !.

@keskiverto &@whitenite1 : thanks for the notes I appreciate them !.

@salem : No Salem it does not matter actually this is another presentation used in switch just to reduce the lines see what @dhayden did .

thanks guys really !