for(ch=0;ch<=127;ch++)

    void main()

{

char ch;

for(ch=0;ch<=127;ch++)

printf(“%c   %d \n“, ch, ch);

}

Answer:

    Implementaion dependent

Explanation:

The char type may be signed or unsigned by default. If it is signed then ch++ is executed after ch reaches 127 and rotates back to -128. Thus ch is always smaller than 127.

Blog Author: Vijay Kumar

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int k = *ip/*jp;

    void main()

{

int i=10, j=2;

int *ip= &i, *jp = &j;

int k = *ip/*jp;

printf(“%d”,k);

}  

Answer:

Compiler Error: “Unexpected end of file in comment started in line 5”.

Explanation:

The programmer intended to divide two integers, but by the “maximum munch” rule, the compiler treats the operator sequence / and * as /* which happens to be the starting of comment. To force what is intended by the programmer,

int k = *ip/ *jp;

// give space explicity separating / and *

//or

int k = *ip/(*jp);

// put braces to force the intention 

will solve the problem. 

Blog Author: Vijay Kumar

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Which version do you prefer of the following two,

    Which version do you prefer of the following two,

1) printf(“%s”,str); // or the more curt one

2) printf(str);

Answer & Explanation:

Prefer the first one. If the str contains any  format characters like %d then it will result in a subtle bug.

Blog Author: Vijay Kumar

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gets() vs fgets()

    char inputString[100] = {0};

To get string input from the keyboard which one of the following is better?

    1) gets(inputString)

    2) fgets(inputString, sizeof(inputString), fp)

Answer & Explanation:

The second one is better because gets(inputString) doesn't know the size of the string passed and so, if a very big input (here, more than 100 chars) the charactes will be written past the input string. When fgets is used with stdin performs the same operation as gets but is safe.

Blog Author: Vijay Kumar

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sizeof pointer

    void main()

{

printf(“sizeof (void *) = %d \n“, sizeof( void *));

    printf(“sizeof (int *)    = %d \n”, sizeof(int *));

    printf(“sizeof (double *)  = %d \n”, sizeof(double *));

    printf(“sizeof(struct unknown *) = %d \n”, sizeof(struct unknown *));

    }

Answer   :

sizeof (void *) = 2

sizeof (int *)    = 2

sizeof (double *)  =  2

sizeof(struct unknown *) =  2

Explanation:

The pointer to any type is of same size.

Blog Author: Vijay Kumar

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Is the following code legal? (5)

    Is the following code legal?

void main()

{

typedef struct a aType;

aType someVariable;

struct a

{

int x;

      aType *b;

              };

}

Answer:

         No

Explanation:

         When the declaration,

typedef struct a aType;

is encountered body of struct a is not known. This is known as ‘incomplete types’.

Blog Author: Vijay Kumar

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Is the following code legal? (4)

    Is the following code legal?

typedef struct a aType;

struct a

{

int x;

aType *b;

};

Answer:

    Yes

Explanation:

The typename aType is known at the point of declaring the structure, because it is already typedefined.

Blog Author: Vijay Kumar

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Is the following code legal? (3)

    Is the following code legal?

typedef struct a

    {

int x;

 aType *b;

    }aType

Answer:

         No

Explanation:

The typename aType is not known at the point of declaring the structure (forward references are not made for typedefs).

Blog Author: Vijay Kumar

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Is the following code legal? (2)

 Is the following code legal?

struct a

    {

int x;

            struct a *b;

    }

Answer:

Yes.

Explanation:

*b is a pointer to type struct a and so is legal. The compiler knows, the size of the pointer to a structure even before the size of the structure

is determined(as you know the pointer to any type is of same size). This type of structures is known as ‘self-referencing’ structure.

Blog Author: Vijay Kumar

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