Function parameters - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function with pointer parameter

What is the output of this C program?

C

#include <stdio.h>

void update(int *p) {
    *p = *p + 5;
}

int main() {
    int x = 10;
    update(&x);
    printf("%d\n", x);
    return 0;
}

A 15

B 10

C 5

D Compilation error

💡 Hint

Remember that passing a pointer allows the function to modify the original variable.

The function 'update' receives a pointer to 'x' and adds 5 to the value it points to. So 'x' becomes 15.

❓ Predict Output

intermediate

Output of function with array parameter

What will this program print?

C

#include <stdio.h>

void modify(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        arr[i] += 1;
    }
}

int main() {
    int nums[3] = {1, 2, 3};
    modify(nums, 3);
    for (int i = 0; i < 3; i++) {
        printf("%d ", nums[i]);
    }
    return 0;
}

A 1 2 3

B 0 1 2

C 2 3 4

D Compilation error

💡 Hint

Arrays passed to functions can be modified inside the function.

The function adds 1 to each element of the array, so the output is '2 3 4 '.

❓ Predict Output

advanced

Output of function with const pointer parameter

What is the output of this program?

C

#include <stdio.h>

void printValue(const int *p) {
    // *p = 10; // Uncommenting this line causes error
    printf("%d\n", *p);
}

int main() {
    int x = 7;
    printValue(&x);
    return 0;
}

A Runtime error

B 10

C Compilation error due to assignment to const pointer

D 7

💡 Hint

The function only reads the value pointed to, it does not modify it.

The function prints the value pointed to by 'p', which is 7. The commented line would cause a compile error if uncommented.

❓ Predict Output

advanced

Output of function with multiple parameters and default values (simulate)

What is the output of this program?

C

#include <stdio.h>

void greet(char *name, int times) {
    for (int i = 0; i < times; i++) {
        printf("Hello, %s!\n", name);
    }
}

int main() {
    greet("Alice", 2);
    return 0;
}

A

Hello, Alice!
Hello, Alice!

B

Hello, Alice!

C Compilation error: default parameters not supported

D Runtime error

💡 Hint

C does not support default parameters, so both arguments must be passed.

The function prints the greeting twice because 'times' is 2.

🧠 Conceptual

expert

Behavior of function parameters with struct pointers

Consider this code snippet. What will be the value of 'p.age' after calling 'updatePerson(&p);'?

C

typedef struct {
    int age;
} Person;

void updatePerson(Person *person) {
    person->age = 30;
}

int main() {
    Person p = {25};
    updatePerson(&p);
    // What is p.age here?
    return 0;
}

A 25

B 30

C Undefined behavior

D Compilation error

💡 Hint

Passing a pointer to a struct allows modifying its fields inside the function.

The function sets the 'age' field of the struct pointed to by 'person' to 30, so 'p.age' becomes 30.