Output of C Programs | Set 4

Predict the output of below programs

Question 1

#include‹stdio.h› int main() {     struct site     {         char name[] = "GeeksforGeeks";         int no_of_pages = 200;     };     struct site *ptr;     printf("%d",ptr->no_of_pages);     printf("%s",ptr->name);     getchar();     return 0; }

Output:
Compiler error

Explanation:
Note the difference between structure/union declaration and variable declaration. When you declare a structure, you actually declare a new data type suitable for your purpose. So you cannot initialize values as it is not a variable declaration but a data type declaration.

Reference:
http://www.lix.polytechnique.fr/~liberti/public/computing/prog/c/C/SYNTAX/struct.html

Question 2

int main() {     char a[2][3][3] = {'g','e','e','k','s','f','o',                            'r','g','e','e','k','s'};     printf("%s ", **a);     getchar();     return 0; }

Output:
geeksforgeeks

Explanation:
We have created a 3D array that should have 2*3*3 (= 18) elements, but we are initializing only 13 of them. In C when we initialize less no of elements in an array all uninitialized elements become ‘\0′ in case of char and 0 in case of integers.

Question 3

int main() {    char str[]= "geeks\nforgeeks";    char *ptr1, *ptr2;           ptr1 = &str[3];    ptr2 = str + 5;    printf("%c", ++*str - --*ptr1 + *ptr2 + 2);    printf("%s", str);       getchar();    return 0; }

Output:
heejs
forgeeks

Explanation:
Initially ptr1 points to ‘k’ and ptr2 points to ‘\n’ in “geeks\nforgeeks”. In print statement value at str is incremented by 1 and value at ptr1 is decremented by 1. So string becomes “heejs\nforgeeks” .

First print statement becomes
printf(“%c”, ‘h’ – ‘j’ + ‘n’ + 2)

‘h’ – ‘j’ + ‘\n’ + 2 = -2 + ‘\n’ + 2 = ‘\n’

First print statements newline character. and next print statement prints “heejs\nforgeeks”.

Question 4

#include <stdio.h> int fun(int n) {     int i, j, sum = 0;     for(i = 1;i<=n;i++)         for(j=i;j<=i;j++)             sum=sum+j;     return(sum); }   int main() {     printf("%d", fun(15));     getchar();     return 0; }

Output: 120
Explanation: fun(n) calculates sum of first n integers or we can say it returns n(n+1)/2.

Question 5

#include <stdio.h> int main() {     int c = 5, no = 1000;     do {         no /= c;     } while(c--);       printf ("%d\n", no);     return 0; }

Output: Exception – Divide by zero

Explanation: There is a bug in the above program. It goes inside the do-while loop for c = 0 also. Be careful when you are using do-while loop like this!!