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Beginner C/C++ Exercises

Decimal to Binary

Convert a positive decimal integer to binary.

What is Decimal to Binary?

Repeated division by two produces binary digits from least significant to most significant.

Important points

  • Compile with warnings enabled and fix every warning.
  • Know the lifetime and type of every value.
  • Validate input and keep array bounds explicit.

C and C++ code examples

C
Run code →
main.c
#include <stdio.h>
int main(void) {
    unsigned number = 13, value = number; int bits[32], count = 0;
    // Store remainders generated from right to left.
    do { bits[count++] = value % 2; value /= 2; } while (value);
    printf("%u = ", number); while (count) printf("%d", bits[--count]); puts("");
}
Result of running the code
13 = 1101
C++
Run code →
main.cpp
#include <bitset>
#include <iostream>
#include <string>
int main() {
    unsigned number = 13;
    // Remove leading zeroes from a fixed-width bitset string.
    std::string bits = std::bitset<32>(number).to_string();
    bits.erase(0, bits.find_first_not_of('0'));
    std::cout << number << " = " << bits << '\n';
}
Result of running the code
13 = 1101

C and C++ comparison

Store remainders and print them in reverse order because division discovers the final digit first.

C

C exposes small procedural APIs and makes representation details explicit.

C++

C++ retains the low-level model while adding safer library types and abstractions.

Practice exercises

Run both versions, then modify them to observe the different language guarantees.

  • Add invalid and boundary-value inputs.
  • Compile with -Wall -Wextra -Wpedantic.
  • Move reusable declarations into a header and implementation file.

Practice with a challenge

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