C Constants, Literals, and Best Practices

#include <stdio.h>

// Preprocessor constants (no memory allocation)
#define PI 3.1415926535
#define MAX_USERS 100
#define COMPANY_NAME "Nikhil LearnHub"
#define NEWLINE '\n'

// Constant variables (allocates memory)
const int DAYS_IN_WEEK = 7;
const float GRAVITY = 9.81;
const char TAB = '\t';

int main() {
    // Integer constants
    int decimal = 100;
    int octal = 0144;      // Octal: starts with 0
    int hexadecimal = 0x64; // Hexadecimal: starts with 0x
    
    // Floating point constants
    float regular = 3.14;
    float scientific = 3.14e2;  // 3.14 × 10² = 314.0
    
    // Character constants
    char letter = 'A';
    char escape = '\n';    // Newline character
    
    // String constants
    char greeting[] = "Hello, C Programmers!";
    
    printf("PI: %.10f%c", PI, NEWLINE);
    printf("Max Users: %d%c", MAX_USERS, NEWLINE);
    printf("Days in Week: %d%c", DAYS_IN_WEEK, NEWLINE);
    printf("Gravity: %.2f m/s²%c", GRAVITY, NEWLINE);
    printf("Company: %s%c", COMPANY_NAME, NEWLINE);
    
    return 0;
}

#include <stdio.h>

// Global variables (declared outside functions)
int globalCounter = 0;
const double TAX_RATE = 0.18;

int main() {
    // Valid variable declarations
    int age = 25;
    float _temperature = 36.6;
    char firstInitial = 'J';
    double accountBalance = 1250.75;
    
    // Multiple declarations of same type
    int x, y, z;
    float width = 10.5, height = 20.3, depth;
    
    // Declaration with initialization
    int counter = 0;
    char newline = '\n';
    
    // Using the variables
    x = 10;
    y = 20;
    z = x + y;
    
    depth = width * height;
    
    printf("Age: %d\n", age);
    printf("Temperature: %.1f\n", _temperature);
    printf("Initial: %c\n", firstInitial);
    printf("Sum: %d\n", z);
    printf("Volume: %.2f\n", depth);
    printf("Tax Rate: %.2f\n", TAX_RATE);
    
    // Redeclaration is NOT allowed
    // int age = 30; // ERROR: redeclaration of 'age'
    
    // Reassignment is allowed
    age = 30; // OK: changing value
    printf("New Age: %d\n", age);
    
    return 0;
}

#include <stdio.h>
#include <stdbool.h>

// Constants (UPPER_SNAKE_CASE)
#define MAX_STUDENTS 100
#define PI 3.1415926535

// Global variables (descriptive names)
int studentCount = 0;
float classAverage = 0.0;

// Function prototypes (camelCase for functions)
float calculateAverage(int scores[], int count);
bool isValidScore(int score);
void printStudentReport(int id, char name[], float grade);

int main() {
    // Local variables (camelCase or snake_case)
    int testScores[MAX_STUDENTS];
    int currentScore;
    bool isProcessingComplete = false;
    char studentName[50];
    
    // Loop counter (short names acceptable)
    for (int i = 0; i < 10; i++) {
        testScores[i] = i * 10;
    }
    
    // Boolean variables (prefix with 'is', 'has', 'can')
    bool hasPassedExam = true;
    bool isEligibleForScholarship = false;
    
    // Pointer variables (prefix with 'p' optionally)
    int *pScore = &testScores[0];
    char *pName = studentName;
    
    // Arrays (plural names)
    float temperatures[7];
    char fileNames[20][100];
    
    printf("Maximum students: %d\n", MAX_STUDENTS);
    printf("PI value: %.10f\n", PI);
    
    return 0;
}

float calculateAverage(int scores[], int count) {
    int total = 0;
    for (int i = 0; i < count; i++) {
        total += scores[i];
    }
    return (float)total / count;
}

bool isValidScore(int score) {
    return (score >= 0 && score <= 100);
}

/*
 * File: calculator.c
 * Author: Nikhil LearnHub
 * Description: Basic arithmetic operations with input validation
 * Created: 2024
 * Version: 1.0
 */

#include <stdio.h>
#include <stdbool.h>

// Constants
#define MAX_OPERAND 1000.0
#define MIN_OPERAND -1000.0

/**
 * @brief Validates if a number is within acceptable range
 * @param number The number to validate
 * @return true if number is within range, false otherwise
 */
bool isValidOperand(double number) {
    return (number >= MIN_OPERAND && number <= MAX_OPERAND);
}

/**
 * @brief Calculates the sum of two numbers
 * @param a First operand
 * @param b Second operand
 * @return Sum of a and b
 * @note Returns 0.0 if operands are invalid
 */
double add(double a, double b) {
    // Validate inputs before processing
    if (!isValidOperand(a) || !isValidOperand(b)) {
        printf("Error: Operand out of range\n");
        return 0.0;
    }
    
    return a + b;
}

/**
 * @brief Calculates the quotient of two numbers
 * @param dividend The number to be divided
 * @param divisor The number to divide by
 * @return Quotient of dividend ÷ divisor
 * @note Returns 0.0 if divisor is zero or operands are invalid
 */
double divide(double dividend, double divisor) {
    // Check for division by zero
    if (divisor == 0.0) {
        printf("Error: Division by zero\n");
        return 0.0;
    }
    
    // Validate operands
    if (!isValidOperand(dividend) || !isValidOperand(divisor)) {
        printf("Error: Operand out of range\n");
        return 0.0;
    }
    
    return dividend / divisor;
}

int main() {
    double num1, num2, result;
    
    // Get user input
    printf("Enter first number: ");
    scanf("%lf", &num1);
    
    printf("Enter second number: ");
    scanf("%lf", &num2);
    
    // Perform addition
    result = add(num1, num2);
    printf("Sum: %.2f\n", result);
    
    // Perform division
    result = divide(num1, num2);
    printf("Quotient: %.2f\n", result);
    
    return 0;
}