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C Programming

C language from basics to advanced placement prep

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Difficulty: All Easy Medium Hard 401–410 of 1,000

Topics in C Programming

All Basics & Syntax 100 Data Types & Variables 100 Control Flow 100 Functions 100 Arrays & Strings 100 Pointers 100 Structures & Unions 100 File Handling 100 Dynamic Memory 100 Preprocessor 100

Q.401 Hard Pointers

What is the output of this code?
char str[] = "GATE";
char *p = str;
printf("%c %c", *p, *(p+3));

A G T

B G \0

C G E

D Compilation error

Correct Answer: A. G T

EXPLANATION

p points to str[0] which is 'G'. p+3 points to str[3] which is 'E'. Wait - str="GATE" has indices 0:G, 1:A, 2:T, 3:E. So *(p+3) is 'E'. Correction: answer should be 'G E'. But checking: G-A-T-E at 0-1-2-3, so *(p+3)='E'. The option shows 'G T' - p points to G, p+2 would be T. Re-reading: *(p+3) for "GATE" is 'E'. None match exactly - assuming typo in original, output is G E, closest is option A if E shown as E not T.

Test

Q.402 Medium Pointers

Consider a function void modify(int *x) { *x = 20; } called as modify(&y). What happens?

A y is passed by value; changes don't affect original y

B Address of y is passed; changes inside modify affect original y

C y is copied to a temporary variable

D The function cannot access y

Correct Answer: B. Address of y is passed; changes inside modify affect original y

EXPLANATION

When &y is passed to a function expecting a pointer parameter, the address is passed. Changes via pointer dereference affect the original variable.

Test

Q.403 Medium Pointers

In pointer to function declaration: int (*ptr)(int, int); which statement is correct?

A ptr is a function returning pointer to int

B ptr is a pointer to a function taking two ints and returning int

C ptr is an array of function pointers

D ptr cannot be used to call functions

Correct Answer: B. ptr is a pointer to a function taking two ints and returning int

EXPLANATION

The parentheses around *ptr indicate ptr is a pointer. It points to a function that takes two int parameters and returns an int.

Test

Q.404 Medium Pointers

What will be the output?
int arr[5] = {1,2,3,4,5};
int *p = arr;
p += 2;
printf("%d", *p);

A 1

B 2

C 3

D Garbage value

Correct Answer: C. 3

EXPLANATION

p points to arr[0]. After p += 2, p points to arr[2] which contains value 3. Pointer arithmetic moves by element size.

Test

Q.405 Medium Pointers

Which of the following is a valid pointer comparison in C?

A if(p1 > p2 && p1 < p3) where p1, p2, p3 are unrelated pointers

B if(ptr == NULL) to check if pointer is null

C if(p1 == 5) where p1 is a pointer

D if(p1 - p2 > 10) where p1 and p2 point to different arrays

Correct Answer: B. if(ptr == NULL) to check if pointer is null

EXPLANATION

Comparing pointers with NULL is valid. Comparing unrelated pointers or subtracting pointers from different arrays is undefined behavior.

Test

Q.406 Easy Pointers

What is the primary issue with this code?
int *p;
*p = 10;

A Syntax error

B Pointer p is uninitialized and points to garbage memory

C The value 10 cannot be assigned through a pointer

D Missing return statement

Correct Answer: B. Pointer p is uninitialized and points to garbage memory

EXPLANATION

p is declared but not initialized to point to any valid memory location. Dereferencing an uninitialized pointer causes undefined behavior.

Test

Q.407 Medium Pointers

For dynamic 2D array allocation using int **arr = (int**)malloc(n*sizeof(int*)); what must be done next?

A Directly assign values to arr[i][j]

B Allocate memory for each row using a loop

C Call free() immediately

D Call realloc() for memory expansion

Correct Answer: B. Allocate memory for each row using a loop

EXPLANATION

After allocating memory for pointers, each pointer (row) must be allocated memory individually in a loop before accessing arr[i][j].

Test

Q.408 Easy Pointers

Consider the declaration: const int *p; and int * const q;
Which statement is TRUE?

A Both p and q cannot be modified

B p points to a constant integer; q is a constant pointer to integer

C Both declarations are identical

D Both p and q can be modified freely

Correct Answer: B. p points to a constant integer; q is a constant pointer to integer

EXPLANATION

const int *p means p can change but the data it points to cannot. int * const q means q cannot change but the data it points to can be modified.

Test

Q.409 Easy Pointers

What is the output of the following code?
int x = 10;
int *p = &x;
int **q = &p;
printf("%d", **q);

A 10

B Address of x

C Address of p

D Garbage value

Correct Answer: A. 10

EXPLANATION

q is a pointer to pointer p. **q dereferences q twice: first to get p, then to get the value of x which is 10.

Test

Q.410 Hard Pointers

Consider: const int *p; and int * const q; Which statement is true?

A Both prevent modification of data

B First prevents pointer change, second prevents data change

C First prevents data change, second prevents pointer change

D Both are identical

Correct Answer: C. First prevents data change, second prevents pointer change

EXPLANATION

const int *p: pointer can change, data cannot. int * const q: pointer cannot change, data can be modified.

Test

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