Example: Rainfall Statistics (Sentinel Value) in C

// Rainfall Statistics (Sentinel Value)
#include <stdio.h>
#include <float.h> // For FLT_MAX and FLT_MIN

int main() {
    // Step 1: Declare variables for sum, count, min, max, and current input.
    float currentRate;
    float sum = 0.0f;
    int count = 0;
    float lowestRate = FLT_MAX; // Initialize with largest possible float value
    float highestRate = FLT_MIN; // Initialize with smallest possible float value

    // Step 2: Prompt for input with instructions for sentinel value.
    printf("Enter rainfall rates (mm/hour). Enter -1 to stop.\n");

    // Step 3: Loop to get rainfall rates until the sentinel is entered.
    while (1) { // Infinite loop, will break manually
        printf("Enter rate: ");
        scanf("%f", &currentRate);

        if (currentRate == -1) {
            break; // Exit loop if sentinel value is entered
        }

        // Validate positive rain rate, or allow 0 for no rain
        if (currentRate < 0) {
            printf("Rainfall rates cannot be negative. Please enter a valid rate or -1 to stop.\n");
            continue; // Skip to next iteration without processing invalid input
        }

        // Step 4: Update sum, count, min, and max.
        sum += currentRate;
        count++;

        if (currentRate < lowestRate) {
            lowestRate = currentRate;
        }
        if (currentRate > highestRate) {
            highestRate = currentRate;
        }
    }

    // Step 5: Check if any valid rates were entered before calculating average.
    if (count > 0) {
        float averageRate = sum / count;
        printf("\n--- Rainfall Statistics ---\n");
        printf("Average Rainfall Rate: %.2f mm/hour\n", averageRate);
        printf("Lowest Rainfall Rate: %.2f mm/hour\n", lowestRate);
        printf("Highest Rainfall Rate: %.2f mm/hour\n", highestRate);
    } else {
        printf("\nNo rainfall rates were entered.\n");
    }

    return 0;
}