File Character and Line Coutning

#include <stdio.h>
#include <ctype.h>
#define MAX_SIZE 100

int main() {
    FILE* file_ptr;
    file_ptr = fopen("input.txt", "r");
    if (!file_ptr) {
        perror("File opening failed");
        return 1;
    }

    int line_count = 0;
    int char_count = 0;
    char buffer[MAX_SIZE];
    
    while (fgets(buffer, MAX_SIZE, file_ptr)) {
        line_count++;
    }
    
    rewind(file_ptr);
    
    int current_char;
    while ((current_char = fgetc(file_ptr)) != EOF) {
        if (!isspace(current_char)) {
            char_count++;
        }
    }
    
    printf("File analysis results:\n");
    printf("Total lines: %d\n", line_count);
    printf("Non-whitespace characters: %d\n", char_count);
    
    fclose(file_ptr);
    return 0;
}

Student Exam Processing System

#include <stdio.h>
#include <string.h>
#define MAX_STUDENTS 10

typedef struct {
    long exam_id;
    char student_name[20];
    float theory_score;
    float practical_score;
    float total_score;
    char status[10];
} Student;

void load_student_data(Student students[], int count);
void save_results(Student students[], int count);
void display_results(Student students[], int count);
int evaluate_students(Student all[], int total, Student passed[]);

int main() {
    Student all_students[MAX_STUDENTS];
    Student passed_students[MAX_STUDENTS];
    int passed_count;
    
    printf("Loading %d student records...\n", MAX_STUDENTS);
    load_student_data(all_students, MAX_STUDENTS);
    
    passed_count = evaluate_students(all_students, MAX_STUDENTS, passed_students);
    
    printf("\nExam results:\n");
    display_results(all_students, MAX_STUDENTS);
    save_results(passed_students, passed_count);
    
    float pass_percentage = (float)passed_count / MAX_STUDENTS * 100;
    printf("\nPass rate: %.2f%%\n", pass_percentage);
    
    return 0;
}

void display_results(Student students[], int count) {
    printf("ID\t\tName\t\tTheory\tPractical\tTotal\t\tStatus\n");
    for (int i = 0; i < count; i++) {
        printf("%ld\t%s\t%.2f\t%.2f\t\t%.2f\t\t%s\n", 
               students[i].exam_id, students[i].student_name,
               students[i].theory_score, students[i].practical_score,
               students[i].total_score, students[i].status);
    }
}

void load_student_data(Student students[], int count) {
    FILE* input_file = fopen("students.txt", "r");
    if (!input_file) {
        perror("Failed to open input file");
        return;
    }
    
    for (int i = 0; i < count; i++) {
        fscanf(input_file, "%ld %s %f %f", 
              &students[i].exam_id, students[i].student_name,
              &students[i].theory_score, &students[i].practical_score);
    }
    fclose(input_file);
}

void save_results(Student students[], int count) {
    FILE* output_file = fopen("passed_students.txt", "w");
    if (!output_file) {
        perror("Failed to create output file");
        return;
    }
    
    fprintf(output_file, "ID\t\tName\t\tTheory\tPractical\tTotal\t\tStatus\n");
    for (int i = 0; i < count; i++) {
        fprintf(output_file, "%ld\t%s\t%.2f\t%.2f\t\t%.2f\t\t%s\n",
               students[i].exam_id, students[i].student_name,
               students[i].theory_score, students[i].practical_score,
               students[i].total_score, students[i].status);
    }
    fclose(output_file);
}

int evaluate_students(Student all[], int total, Student passed[]) {
    int pass_count = 0;
    
    for (int i = 0; i < total; i++) {
        all[i].total_score = all[i].theory_score + all[i].practical_score;
        
        if (all[i].total_score >= 60) {
            strcpy(all[i].status, "Passed");
            passed[pass_count++] = all[i];
        } else {
            strcpy(all[i].status, "Failed");
        }
    }
    return pass_count;
}

Random Seelction and File Output

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#define MAX_ENTRIES 100

int main() {
    char entries[MAX_ENTRIES][MAX_ENTRIES];
    char winners[5][MAX_ENTRIES];
    int selected[MAX_ENTRIES] = {0};
    
    FILE* input_file = fopen("entries.txt", "r");
    if (!input_file) {
        perror("Failed to open input file");
        return 1;
    }
    
    int entry_count = 0;
    while (fgets(entries[entry_count], MAX_ENTRIES, input_file)) {
        entry_count++;
    }
    fclose(input_file);
    
    srand(time(NULL));
    printf("Selected winners:\n");
    
    for (int i = 0; i < 5; i++) {
        int random_index;
        do {
            random_index = rand() % entry_count;
        } while (selected[random_index]);
        
        selected[random_index] = 1;
        strcpy(winners[i], entries[random_index]);
        printf("%s", winners[i]);
    }
    
    printf("\nEnter output filename: ");
    char filename[MAX_ENTRIES];
    scanf("%s", filename);
    
    FILE* output_file = fopen(filename, "w");
    if (!output_file) {
        perror("Failed to create output file");
        return 1;
    }
    
    for (int i = 0; i < 5; i++) {
        fputs(winners[i], output_file);
    }
    
    fclose(output_file);
    return 0;
}