C program topic 2

                                                                           

1. Which is valid C expression?
a) int my_num = 100,000;
b) int my_num = 100000;
c) int my num = 1000;
d) int $my_num = 10000;
View Answer

Answer: b
Explanation: Space, comma and $ cannot be used in a variable name.

2. What is the output of this C code?

1.     #include <stdio.h>

2.     int main()

3.     {

4.         printf("Hello World! %d \n", x);

5.         return 0;

6.     }

a) Hello World! x;
b) Hello World! followed by a junk value
c) Compile time error
d) Hello World!
View Answer

Answer: c
Explanation: It results in an error since x is used without declaring the variable x.
Output:
$ cc pgm1.c
pgm1.c: In function ‘main’:
pgm1.c:4: error: ‘x’ undeclared (first use in this function)
pgm1.c:4: error: (Each undeclared identifier is reported only once
pgm1.c:4: error: for each function it appears in.)

3. What is the output of this C code?

1.     #include <stdio.h>

2.     int main()

3.     {

4.         int y = 10000;

5.         int y = 34;

6.         printf("Hello World! %d\n", y);

7.         return 0;

8.     }

a) Compile time error
b) Hello World! 34
c) Hello World! 1000
d) Hello World! followed by a junk value
View Answer

Answer: a
Explanation: Since y is already defined, redefining it results in an error.
Output:
$ cc pgm2.c
pgm2.c: In function ‘main’:
pgm2.c:5: error: redefinition of ‘y’
pgm2.c:4: note: previous definition of ‘y’ was here

4. Which of the following is not a valid variable name declaration?
a) float PI = 3.14;
b) double PI = 3.14;
c) int PI = 3.14;
d) #define PI 3.14
View Answer

Answer: d
Explanation: #define PI 3.14 is a macro preprocessor, it is a textual substitution.

5. What will happen if the below program is executed?

1.     #include <stdio.h>

2.     int main()

3.     {

4.         int main = 3;

5.         printf("%d", main);

6.         return 0;

7.     }

a) It will cause a compile-time error
b) It will cause a run-time error
c) It will run without any error and prints 3
d) It will experience infinite looping
View Answer

Answer: c
Explanation: A C program can have same function name and same variable name.
$ cc pgm3.c
$ a.out
3

6. What is the problem in following variable declaration?

float 3Bedroom-Hall-Kitchen?;

a) The variable name begins with an integer
b) The special character ‘-‘
c) The special character ‘?’
d) All of the mentioned
View Answer

Answer: d
Explanation: A variable name cannot start with an integer, along with that the C compiler
interprets the ‘-‘ and ‘?’ as a minus operator and a question mark operator respectively.

7. Comment on the output of this C code?

1.     #include <stdio.h>

2.     int main()

3.     {

4.         int ThisIsVariableName = 12;

5.         int ThisIsVariablename = 14;

6.         printf("%d", ThisIsVariablename);

7.         return 0;

8.     }

a) The program will print 12
b) The program will print 14
c) The program will have a runtime error
d) The program will cause a compile-time error due to redeclaration
View Answer

Answer: b
Explanation: Variable names ThisIsVariablename and ThisIsVariableName are both distinct as C is case sensitive.
Output:
$ cc pgm4.c
$ a.out
14

8. Which of the following cannot be a variable name in C?
a) volatile
b) true
c) friend
d) export
View Answer

Answer: a
Explanation: volatile is C keyword.