C questions in placement tests and university exams are rarely about syntax alone. Most of what you will find here is output prediction, pointer arithmetic, arrays and strings, structures and unions, storage classes, recursion, and file handling. The explanations walk through memory behaviour step by step, which is usually where the confusion sits rather than in the code itself.
Which of the following is NOT a fundamental data type in C?
Answer: C
C has 5 fundamental data types: int, float, double, char, and void. 'string' is not a fundamental type; it's created using char arrays.
Q.2Easy
What is the size of an 'int' variable in a 32-bit system?
Answer: B
In a 32-bit system, an int is typically 4 bytes (32 bits). However, the C standard only guarantees it's at least 2 bytes, so technically it's compiler-dependent. But in practice, 4 bytes is standard.
Q.3Easy
Which variable declaration is correct in C?
Answer: C
Variable names must start with a letter or underscore, followed by letters, digits, or underscores. Option C follows this rule correctly.
Q.4Medium
What will be the output of the following code? int x = 5; float y = x; printf("%f", y);
Answer: A
Implicit type conversion occurs from int to float. The value 5 is converted to 5.0 and printed as 5.000000 with %f format specifier.
Q.5Medium
Which of the following occupies maximum memory in a 64-bit system?
Answer: B
In a 64-bit system, long double typically occupies 16 bytes (128 bits), which is the maximum among these options.
Q.6Medium
What is the range of unsigned int in a 32-bit system?
Answer: B
Unsigned int uses all 32 bits for magnitude, giving range 0 to 2^32 - 1 (0 to 4,294,967,295).
Q.7Easy
Which keyword is used to declare a variable that cannot be modified?
Answer: B
'const' keyword makes a variable constant and immutable after initialization.
Q.8Medium
What is the difference between 'static' and 'extern' variables?
Answer: B
static restricts variable visibility to the current file; extern declares a variable defined elsewhere with global scope.
Q.9Medium
What is the output of the following code? int x = 10; int *p = &x; printf("%d", *p);
Answer: A
p is a pointer to x. *p dereferences the pointer, giving the value of x, which is 10.
Q.10Easy
Which of the following is a derived data type in C?
Answer: B
Derived data types are created from fundamental types. Arrays, pointers, structures, and unions are derived types.
Q.11Hard
What will be the size of the following structure? struct test { char c; int i; float f; };
Answer: D
Size depends on compiler's padding and alignment rules. Typically 12 bytes with padding, but varies by system.
Q.12Medium
Which variable storage class has default initialization to 0?
Answer: C
Static variables are automatically initialized to 0 by the compiler.
Q.13Medium
What is the output of this code? float x = 25; printf("%f", x);
Answer: B
25 performs integer division (both operands are int), resulting in 2. This is then converted to float as 2.0.
Q.14Easy
How many bits are used to store a 'short int' in a standard C environment?
Answer: B
Standard C guarantees short int is at least 16 bits (2 bytes). Most systems use exactly 16 bits.
Q.15Medium
What happens when you declare a variable without initializing it?
Answer: B
Auto variables (local variables) contain unpredictable garbage values if not initialized. Static/global variables are initialized to 0.
Q.16Hard
Which of the following correctly demonstrates pointer arithmetic?
Answer: A
Option A shows pointer arithmetic where p++ increments the pointer by the size of int (4 bytes). Other options are regular arithmetic operations.
Q.17Hard
What is the output of the following code? int a = 5; int *p = &a; int **q = &p; printf("%d", **q);
Answer: A
q is a pointer to pointer p. **q dereferences both pointers, giving the value of a, which is 5.
Q.18Medium
Which data type is most suitable for storing a decimal number with high precision?
Answer: C
long double provides maximum precision (typically 80-128 bits) for decimal numbers compared to float (32 bits) and double (64 bits).
Q.19Easy
What is the range of values for a signed char in C?
Answer: B
A signed char occupies 1 byte (8 bits). With sign bit, it ranges from -128 to 127 (2^7 to 2^7-1).
Q.20Easy
Which keyword is used to modify a variable so that it cannot be changed?
Answer: B
The const keyword makes a variable read-only after initialization. Its value cannot be modified during program execution.
