Typedef keyword in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of typedef alias usage

What is the output of this C program using typedef?

C

#include <stdio.h>

typedef unsigned int uint;

int main() {
    uint a = 10;
    printf("%u\n", a);
    return 0;
}

A Compilation error

B 10

C Garbage value

D 0

💡 Hint

typedef creates an alias for a type, so uint is an alias for unsigned int.

The typedef creates 'uint' as an alias for 'unsigned int'. So 'a' is an unsigned int with value 10, printed correctly.

🧠 Conceptual

intermediate

Purpose of typedef keyword

What is the main purpose of the typedef keyword in C?

A To create a new data type with a different name

B To declare a constant variable

C To allocate memory dynamically

D To define a function prototype

💡 Hint

Think about how typedef helps with naming types.

typedef allows you to create a new name (alias) for an existing data type to make code easier to read or manage.

❓ Predict Output

advanced

Output of typedef with struct

What is the output of this C program?

C

#include <stdio.h>

typedef struct {
    int x;
    int y;
} Point;

int main() {
    Point p = {3, 4};
    printf("%d %d\n", p.x, p.y);
    return 0;
}

A Compilation error

B 0 0

C 3 4

D Garbage values

💡 Hint

typedef creates an alias for the struct type named Point.

The typedef defines 'Point' as an alias for the struct. The variable 'p' is initialized with {3,4} and prints those values.

🔧 Debug

advanced

Identify the error with typedef usage

What error will this code produce?

C

typedef int Number;

int main() {
    Number x = 5;
    int Number = 10;
    printf("%d %d\n", x, Number);
    return 0;
}

A Output: 5 10

B Runtime error

C Output: 10 5

D Compilation error: redefinition of 'Number'

💡 Hint

Check if typedef names and variable names can conflict.

The typedef creates an alias 'Number' for int, but then 'Number' is used as a variable name, causing a redefinition error.

🧠 Conceptual

expert

How typedef affects pointer declarations

Given typedef int* IntPtr;, what does IntPtr a, b; declare?

A 'a' is a pointer to int, 'b' is an int

B 'a' is an int, 'b' is a pointer to int

C Both 'a' and 'b' are ints

D Both 'a' and 'b' are pointers to int

💡 Hint

Remember how typedef affects pointer syntax and variable declarations.

typedef creates 'IntPtr' as a pointer to int. In 'IntPtr a, b;', both 'a' and 'b' are pointers to int because the typedef name includes the pointer.