Test your C Programming skills Part 3

Q1. Find the o/p:
main() {

   char *p;

   p="Hello";

   printf("%c\n",*&*p);

}
Ans:

     H

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Q2. Find the o/p:
main() {

   int i=1;

   while (i<=5){      printf("%d",i);      if (i>2)

     i++;

   }

}

fun() {

   here:

   printf("PP");

}
Ans:

Compiler error: Undefined label 'here' in function main

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Q3. Find the o/p:
void main() {

   int i=5;

   printf("%d",i++ + ++i);

}

Ans:

     Output Cannot be predicted exactly.

     Explanation:
     Side effects are involved in the evaluation of i.

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Q4. Find the o/p:
main() {

   int i=1,j=2;

   switch(i) {

   case 1: printf("GOOD");

   break;

   case j: printf("BAD");

   break;

   }

}
Ans:

Compiler Error: Constant expression required in function main.

Explanation:
The case statement can have only constant expressions (this implies that
we cannot use variable names directly so an error).

Note:
Enumerated types can be used in case statements.

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Q5. Find the o/p:
main() {

   int i;

   printf("%d",scanf("%d",&i)); // value 10 is given as input here

}

Ans:

     1

Explanation:
Scanf returns number of items successfully read.Here 10 is given as input
which should have been scanned successfully. So number of items read is 1.

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Q6. Find the o/p:
#define f(g,g2) g##g2

main() {

   int var12=100;

   printf("%d",f(var,12));

}
Ans:

     100

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Q7. Find the o/p:
main() {

   int i=0;

   for(;i++;printf("%d",i)) ;

}
Ans:

     1

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Q8. Find the o/p:
# include < stdio.h >
main() {

   printf("%d", out);

}

int out=100;

Ans:

     Compiler error: undefined symbol out in function main.

Explanation:
The rule is that a variable is available for use from the point of declaration.
Even though a is a global variable, it is not available for main. Hence an error.

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Q9. Find the o/p:
#include <stdio.h>
main() {

   extern out;

   printf("%d", out);

}

int out=100;

Ans:

     100

Explanation:
This is the correct way of writing the previous program.

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Q10. Find the o/p of this:
main( ) {

   int a[ ] = {10,20,30,40,50},j,*p;

   for(j=0; j<5; j++){      printf(“%d” ,*;      a++;    }    p = a;    for(j=0; j<5; j++){      printf(“%d ” ,*p);      p++;    } }

Ans:

Compiler error: lvalue required.

Explanation:
Error is in line with statement a++. The operand must be an lvalue and may be of any of
scalar type for the any operator, array name only when subscripted is an lvalue. Simply array name is a non-modifiable lvalue.

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Q11. Find the o/p:
main() {

   static char *s[ ] = {“black”, “white”, “yellow”, “violet”};

   char **ptr[ ] = {s+3, s+2, s+1, s}, ***p;

   p = ptr;

   **++p;

   printf(“%s”,*--*++p + 3);

}

Ans:

     ck

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Q12. Find the o/p:
main() {
   int i,j;

   for(i=0;i<=10;i++){    j+=5;    assert(i<5); }

Ans:

Runtime error: Abnormal program termination.

Explaination:
assert failed (i<5), ,
asserts are used during debugging to make sure that certain conditions are
satisfied. If assertion fails, the program will terminate reporting the same. After
debugging use,

#undef NDEBUG

and this will disable all the assertions from the source code. Assertion is a
good debugging tool to make use of.

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Q13.What are the files which are automatically opened when a C file is executed?

Ans:

stdin, stdout, stderr (standard input,standard output,standard error).

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