Nested printf (printf inside printf) in C

Predict the output of the following C program with a printf inside printf.

#include<stdio.h>

int main()
{
   int x = 1987;
   printf("%d", printf("%d", printf("%d", x)));
   return(0);
}

Output :

198741

Explanation :
1. Firstly, the innermost printf is executed which results in printing 1987

2. This printf returns total number of digits in 1987 i.e 4. printf() returns number of characters successfully printed on screen. The whole statement reduces to :

printf("%d", printf("%d", 4));

3. The second printf then prints 4 and returns the total number of digits in 4 i.e 1 (4 is single digit number ).

4. Finally, the whole statement simply reduces to :

printf("%d", 1);

5. It simply prints 1 and output will be :

Output:

198741

So, when multiple printf’s appear inside another printf, the inner printf prints its output and returns length of the string printed on the screen to the outer printf.

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