C Programming - MCQ Practice Questions

Which statement is true about nested structures in C?

What happens if you assign a union member and then access another member? struct u { int a; char b; }; u.a = 257; printf("%d", u.b);

How can you initialize a structure array of 10 elements partially in C?

What is the difference between self-referential and recursive structures?

Given union test { int x; char y[4]; }; If you set y[0]=65, y[1]=66, what happens to x?

Which approach is more memory efficient for storing 100 flags: array of char or bit fields in a structure?

In nested structures with pointers, which access method is correct? struct outer { struct inner *ptr; } *o; Accessing inner's member x:

What is the relationship between structure alignment and padding in modern C compilers?

In a structure with flexible array members, which statement is INCORRECT? struct FlexArray { int len; int arr[]; };

What is the output of the following? struct S { int a:3; int b:3; int c:3; }; printf("%zu", sizeof(struct S));

In competitive programming, when should you use union instead of struct?

What will be the output of this code? struct X { int a; float b; }; struct Y { struct X x; int c; }; printf("%zu", sizeof(struct Y));

In a structure, what does the #pragma pack(1) directive do?

If a structure contains a flexible array member, where must it be declared?

In competitive programming, when implementing a graph using adjacency lists, which data structure is most suitable?

If you have a structure with bit fields, which statement about their behavior is true?

What is the output of this complex code? struct S { char c; int i; } s; printf("%lu", sizeof(s));

In competitive programming, when you need a structure that can hold either an integer or a floating-point number (but not both simultaneously) in the most memory-efficient way, which should you use?

What will be the output of the following code? union Test { int a; char b; }; union Test t; t.a = 65; printf("%d %c", t.a, t.b);

In competitive programming for GATE/ISRO 2025, which scenario would union be preferable over structure?