Type modifiers in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of signed and unsigned char addition

What is the output of this C code snippet?

C

#include <stdio.h>

int main() {
    signed char a = 127;
    unsigned char b = 1;
    int c = a + b;
    printf("%d\n", c);
    return 0;
}

A 128

B -128

C 0

D 255

💡 Hint

Remember that signed char max is 127 and unsigned char max is 255. The addition promotes both to int.

The signed char 'a' is 127, unsigned char 'b' is 1. Both are promoted to int before addition. 127 + 1 = 128, which fits in int and prints as 128.

❓ Predict Output

intermediate

Effect of long modifier on integer size

What is the output of this C code?

C

#include <stdio.h>

int main() {
    long int x = 2147483648L;
    printf("%ld\n", x);
    return 0;
}

A 0

B -2147483648

C 2147483648

D Compilation error

💡 Hint

Check the size of long int on a 32-bit or 64-bit system and the literal value.

The literal 2147483648 fits in a long int on 64-bit systems. The output prints the positive number 2147483648.

🔧 Debug

advanced

Why does this code print a negative number?

This code prints a negative number instead of the expected positive value. Why?

C

#include <stdio.h>

int main() {
    unsigned int a = 4000000000U;
    int b = a;
    printf("%d\n", b);
    return 0;
}

A Because 4000000000 is too small for unsigned int.

B Because unsigned int cannot hold values above 32767.

C Because printf with %d expects unsigned int, but got int.

D Because assigning unsigned int to int causes overflow and negative value due to two's complement.

💡 Hint

Think about how large values in unsigned int convert to signed int.

The value 4000000000 exceeds the max of signed int (usually 2147483647). Assigning it to int causes overflow and prints a negative number due to two's complement representation.

📝 Syntax

advanced

Which option causes a compilation error?

Which of the following C declarations will cause a compilation error?

A long long int y;

B unsigned signed int x;

C signed int z;

D unsigned int w;

💡 Hint

Check if 'unsigned signed' is a valid combination.

'unsigned signed int' is invalid because 'unsigned' and 'signed' cannot be combined together for the same variable.

🧠 Conceptual

expert

Size difference between short, int, and long with modifiers

On a typical 64-bit system, which statement about sizes of these types is true?

A short int < int < long int

B short int == int < long int

C short int == int == long int

D short int < int == long int

💡 Hint

Check typical sizes: short is 2 bytes, int and long are usually 4 or 8 bytes on 64-bit.

On a typical 64-bit system (such as Linux with LP64 data model), short int is 2 bytes, int is 4 bytes, long int is 8 bytes, so short int < int < long int.