Multiple Choice Questions and Answers for Data Types and Sizes in C Language

List of C language programming interview questions on “Data Types and Sizes” along with answers, explanations and/or solutions:

1. Comment on the output of this C code?

1.     #include 

2.     int main()

3.     {

4.         int a[5] = {1, 2, 3, 4, 5};

5.         int i;

6.         for (i = 0; i < 5; i++)

7.             if ((char)a[i] == '5')

8.                 printf("%d\n", a[i]);

9.             else

10.                 printf("FAIL\n");

11.     }

a) The compiler will flag an error
b) Program will compile and print the output 5
c) Program will compile and print the ASCII value of 5
d) Program will compile and print FAIL for 5 times

Answer:d

Explanation:The ASCII value of 5 is 53, the char type-casted integral value 5 is 5 only.

Output:
$ cc pgm1.c
$ a.out
FAILED
FAILED
FAILED
FAILED
FAILED

2. The format identifier ‘%i’ is also used for _____ data type?

a) char
b) int
c) float
d) double

Answer:b

Explanation:Both %d and %i can be used as a format identifier for int data type.

3. Which data type is most suitable for storing a number 65000 in a 32-bit system?

a) signed short
b) unsigned short
c) long
d) int

Answer:b

Explanation:65000 comes in the range of short (16-bit) which occupies the least memory. Signed short ranges from -32768 to 32767 and hence we should use unsigned short.

4. Which of the following is a User-defined data type?

a) typedef int Boolean;
b) typedef enum {Mon, Tue, Wed, Thu, Fri} Workdays;
c) struct {char name[10], int age};
d) all of the mentioned

Answer:d

Explanation:typedef and struct are used to define user-defined data types.

5. What is the size of an int data type?

a) 4 Bytes
b) 8 Bytes
c) Depends on the system/compiler
d) Cannot be determined

Answer:c

Explanation:The size of the data types depend on the system.

6. What is the output of this C code?

1.     #include  

2.     int main()

3.     {

4.        signed char chr;

5.        chr = 128;

6.        printf("%d\n", chr);

7.        return 0;

8.     }

a) 128
b) -128
c) Depends on the compiler
d) None of the mentioned

Answer:b

Explanation:signed char will be a negative number.

Output:
$ cc pgm2.c
$ a.out
-128

7. Comment on the output of this C code?

1.     #include  

2.     int main()

3.     {

4.         char c;

5.         int i = 0;

6.         FILE *file;

7.         file = fopen("test.txt", "w+");

8.         fprintf(file, "%c", 'a');

9.         fprintf(file, "%c", -1);

10.         fprintf(file, "%c", 'b');

11.         fclose(file);

12.         file = fopen("test.txt", "r");

13.         while ((c = fgetc(file)) !=  -1)

14.             printf("%c", c);

15.         return 0;

16.     }

a) a
b) Infinite loop
c) Depends on what fgetc returns
d) Depends on the compiler

Answer:a
Explanation:None.
Output:
$ cc pgm3.c
$ a.out
a

8. What is short int in C programming?

a) Basic datatype of C
b) Qualifier
c) short is the qualifier and int is the basic datatype
d) All of the mentioned

Answer:c

9. Comment on the output of this C code?

1.     #include 

2.     int main()

3.     {

4.         float f1 = 0.1;

5.         if (f1 == 0.1)

6.             printf("equal\n");

7.         else

8.             printf("not equal\n");

9.     }

a) equal
b) not equal
c) Output depends on compiler
d) None of the mentioned

Answer:b

Explanation:0.1 by default is of type double which has different representation than float resulting in inequality even after conversion.

Output:
$ cc pgm4.c
$ a.out
not equal

10. Comment on the output of this C code?

1.     #include 

2.     int main()

3.     {

4.         float f1 = 0.1;

5.         if (f1 == 0.1f)

6.             printf("equal\n");

7.         else

8.             printf("not equal\n");

9.     }

a) equal
b) not equal
c) Output depends on compiler
d) None of the mentioned

Answer:a

Explanation:0.1f results in 0.1 to be stored in floating point representations.

Output:
$ cc pgm5.c
$ a.out
equal

11. What is the output of this C code (on a 32-bit machine)?

1.     #include 

2.     int main()

3.     {

4.         int x = 10000;

5.         double y = 56;

6.         int *p = &x;

7.         double *q = &y;

8.         printf("p and q are %d and %d", sizeof(p), sizeof(q));

9.         return 0;

10.     }

a) p and q are 4 and 4
b) p and q are 4 and 8
c) Compiler error
d) p and q are 2 and 8

Answer:a

Explanation:Size of any type of pointer is 4 on a 32-bit machine.

Output:
$ cc pgm6.c
$ a.out
p and q are 4 and 4

12. Which is correct with respect to size of the datatypes?

a) char > int > float
b) int > char > float
c) char < int < double
d) double > char > int

Answer:c

Explanation:char has lesser bytes than int and int has lesser bytes than double in any system

13. What is the output of the following C code(on a 64 bit machine)?

1.     #include 

2.     union Sti

3.     {

4.         int nu;

5.         char m;

6.     };

7.     int main()

8.     {

9.         union Sti s;

10.         printf("%d", sizeof(s));

11.         return 0;

12.     }

a) 8
b) 5
c) 9
d) 4

Answer:d

Explanation:Since the size of a union is the size of its maximum datatype, here int is the largest hence 4.
Output:
$ cc pgm7.c
$ a.out
4

14. What is the output of this C code?

1.     #include 

2.     int main()

3.     {

4.         float x = 'a';

5.         printf("%f", x);

6.         return 0;

7.     }

a) a
b) run time error
c) a.0000000
d) 97.000000

Answer:d

Explanation:Since the ASCII value of a is 97, the same is assigned to the float variable and printed.

Output:
$ cc pgm8.c
$ a.out
97.000000

15. Which of the datatypes have size that is variable?

a) int
b) struct
c) float
d) double

Answer:b

Explanation:Since the size of the structure depends on its fields, it has a variable size.