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;
Answer
Answer: b [Reason:] Space, comma and $ cannot be used in a variable name.
2. What is the output of this C code?
-
#include <stdio.h> -
int main()
-
{ -
printf("Hello World! %d n", x);
-
return 0;
-
}
a) Hello World! x;
b) Hello World! followed by a junk value
c) Compile time error
d) Hello World!
Answer
Answer: c [Reason:] 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?
-
#include <stdio.h> -
int main()
-
{ -
int y = 10000;
-
int y = 34;
-
printf("Hello World! %dn", y);
-
return 0;
-
}
a) Compile time error
b) Hello World! 34
c) Hello World! 1000
d) Hello World! followed by a junk value
Answer
Answer: a [Reason:] 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
Answer
Answer: d [Reason:] #define PI 3.14 is a macro preprocessor, it is a textual substitution.
5. What will happen if the below program is executed?
-
#include <stdio.h> -
int main()
-
{ -
int main = 3;
-
printf("%d", main);
-
return 0;
-
}
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
Answer
Answer: c [Reason:] 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
Answer
Answer: d [Reason:] 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?
-
#include <stdio.h> -
int main()
-
{ -
int ThisIsVariableName = 12;
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int ThisIsVariablename = 14;
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printf("%d", ThisIsVariablename);
-
return 0;
-
}
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
Answer
Answer: b [Reason:] 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
Answer
Answer: a [Reason:] volatile is C keyword.
