Computer Knowledge - MCQ Practice Questions

Variable names in C must start with a letter or underscore, not a digit. _variable is valid. '2var' starts with digit, 'var-name' contains hyphen (invalid), 'var name' contains space (invalid).

The strlen() function returns the length of a string as an int value, representing the number of characters.

Parentheses () have the highest precedence among all operators in C. They are always evaluated first in any expression.

A pointer is a variable that stores the memory address of another variable. It is declared using the * symbol.

malloc() (memory allocation) allocates a block of memory dynamically during program execution and returns a pointer to it.

Arrays in C are declared with square brackets containing the size, followed by initialization in curly braces. Option A is the correct syntax.

In C, if a function's return type is not explicitly specified, it defaults to int. However, modern C standards require explicit return type declaration.

The break statement immediately terminates the loop and transfers control to the statement following the loop.

The arrow operator (->) is used to access structure members through a pointer. The dot operator (.) is used for direct access.

#define is a preprocessor directive used to define symbolic constants (macros) and performs text substitution before compilation.

To explicitly declare a function with no parameters in C, use 'void' as the parameter. int func(); is ambiguous in older C standards.

The pre-increment operator (++x) increments x from 5 to 6 before using its value in printf(). So the output is 6.

ptr[2] is equivalent to *(ptr+2), which dereferences the pointer and returns the value at the third element (index 2).

Linear search checks each element sequentially. In the worst case, it needs to check all n elements, resulting in O(n) time complexity.

ptr is reassigned to point to b. When we dereference ptr using *ptr, we get the value stored at b, which is 10.

Static variables are initialized only once and retain their value throughout the program execution. Their value persists between function calls.

On most modern 32-bit and 64-bit systems, an int is typically 4 bytes (32 bits). However, the exact size can vary depending on the compiler and system architecture.

C does not have a built-in boolean data type. The other options (float, double, char) are all valid primitive data types in C. Boolean functionality is typically implemented using int (0 for false, non-zero for true).

The & operator has two uses in C: (1) When used before a variable, it returns the memory address of that variable (address-of operator), and (2) When used between two integers, it performs a bitwise AND operation.

The const keyword is used in C to declare a constant variable whose value cannot be modified after initialization. Variables declared as const are read-only.