Count Character Frequency in C, C++, Java & Python – Code with Explanation & Examples in Short and Simple

  

C Program

#include <stdio.h>
#include <string.h>
int main() {
    char str[100];
    int freq[256] = {0}; 
    printf("Enter a string: ");
    fgets(str, sizeof(str), stdin);
    for (int i = 0; str[i] != '\0'; i++)
        freq[(unsigned char)str[i]]++;
    for (int i = 0; i < 256; i++)
        if (freq[i] > 0 && i != '\n')
            printf("%c : %d\n", i, freq[i]);
    return 0;
}

C Output

Input:
hello world

Output:
h : 1
e : 1
l : 3
o : 2
  : 1
w : 1
r : 1
d : 1

C++ Program

#include <iostream>
#include <string>
#include <unordered_map>
using namespace std;
int main() {
    string str;
    cout << "Enter a string: ";
    getline(cin, str);
    unordered_map<char,int> freq;
    for(char c : str) freq[c]++;
    for(auto &p : freq) cout << p.first << " : " << p.second << endl;
    return 0;
}

C++ Output

Input:
banana

Output:
b : 1
a : 3
n : 2

JAVA Program

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a string: ");
        String str = sc.nextLine();
        HashMap<Character,Integer> freq = new HashMap<>();
        for(char c : str.toCharArray())
            freq.put(c, freq.getOrDefault(c,0)+1);
        for(Map.Entry<Character,Integer> e : freq.entrySet())
            System.out.println(e.getKey()+" : "+e.getValue());
    }
}

JAVA Output

Input:
programming

Output:
p : 1
r : 2
o : 1
g : 2
a : 1
m : 2
i : 1
n : 1

Python Program

from collections import Counter
s = input("Enter a string: ")
freq = Counter(s)
for k,v in freq.items():
    print(k, ":", v)

Python Output

Input:
mississippi

Output:
m : 1
i : 4
s : 4
p : 2

In-Depth Explanation

Example

Let us consider the word "balloon". The count for each character is:

b → 1

a → 1

l → 2

o → 2

n → 1

This informs us about how many times each character occurs in the string. It is like creating a count-sheet for each character.

Real-Life Analogy

Suppose you are a teacher tallying the number of times every student responds in class. Each student's name is a character, and each response increases his or her count by one. At the end, you have an idea of who contributed most and who contributed least. Similarly, we are tallying character contribution in a string.

Why It Matters

Frequency counting is not merely a fundamental drill. It is the building block of numerous practical problems:

Text compression schemes such as Huffman Coding employ frequency of characters to compress the file.

Cryptography employs frequency analysis to break substitution ciphers.

Spell checking and word suggestion based on letter frequency.

In data analysis, comparing word or letter frequency in logs, books, or tweets provides useful insights.

Learning Insights

This exercise educates beginners:

String iteration – you have to iterate over all characters in the string.

Storage of data – you would require an array or map/dictionary to hold counts.

Checking conditions – making sure you only count valid characters.

It forms a foundation for problems such as finding the most frequent word, anagramming checks, or palindromes with frequencies.

Interview and Real Projects

Interviewers tend to ask this problem as it tests whether you understand:

How to employ arrays or hash maps.

How to process strings effectively.

How to do clean, elegant code with maps/dictionaries.

In actual projects, this concept applies to log analysis (error type counting), natural language processing (frequency of words in a sentence), and file analysis (verifying character frequency for encoding).

SEO-Friendly Closing Paragraph

One of the most valuable programming tasks for beginners is counting frequency of characters in a string, which teaches students about arrays, hash maps, and string traversals. This is a common problem being asked in coding interviews, competitive exams, and programming competitions due to the fact that it serves as the foundation of sophisticated applications such as text mining, encryption, compression, and big data analysis. Through character frequency program practice in C, C++, Java, and Python, students not just learn to handle strings but also develop applied problem-solving skills that are beneficial for real-world projects and job interviews.