diff --git a/src/hello.c b/src/hello.c
index 9d6338f..7f5a152 100644
--- a/src/hello.c
+++ b/src/hello.c
@@ -2,8 +2,8 @@
 #include <stdio.h>
 
 int main(int argc, char *argv[]) {
-  // This is your first C program my friend
-  printf("Hello, RTU World from C Lab in 2025!\n");
+  // My first C program!
+  printf("Hello, RTU World from C Lab in September 2025!\n");
   printf("You passed %d argument(s).\n", argc - 1);
   for (int i = 1; i < argc; ++i) {
     printf("  arg[%d] = %s\n", i, argv[i]);
diff --git a/src/lab2_1 b/src/lab2_1
new file mode 100755
index 0000000..7236e09
Binary files /dev/null and b/src/lab2_1 differ
diff --git a/src/lab2_1.c b/src/lab2_1.c
index 699339a..8e8bdb6 100644
--- a/src/lab2_1.c
+++ b/src/lab2_1.c
@@ -12,8 +12,11 @@
 */
 
 int sum_to_n(int n) {
-    // TODO: implement sum with a for loop
-    return 0; // placeholder
+    int sum=0;
+    for (int i=1; i<=n; i++) {
+        sum +=i;
+    }
+    return sum; // placeholder
 }
 
 int main(void) {
@@ -22,7 +25,11 @@ int main(void) {
     printf("Enter a positive integer n: ");
     scanf("%d", &n);
 
-    // TODO: validate input, call function, and print result
+    if (n<1) {
+        printf("error\n");
+    } else {
+        printf("The sum is: %d\n", sum_to_n(n));
+    }
 
     return 0;
 }
diff --git a/src/lab2_2 b/src/lab2_2
new file mode 100755
index 0000000..614930a
Binary files /dev/null and b/src/lab2_2 differ
diff --git a/src/lab2_2.c b/src/lab2_2.c
index d88ef6d..65b005a 100644
--- a/src/lab2_2.c
+++ b/src/lab2_2.c
@@ -12,8 +12,11 @@
 */
 
 long long factorial(int n) {
-    // TODO: compute factorial iteratively
-    return 1; // placeholder
+    long long res = 1;
+    for (int i=1; i<=n; i++) {
+        res *= i;
+    }
+    return res; // placeholder
 }
 
 int main(void) {
@@ -22,7 +25,11 @@ int main(void) {
     printf("Enter a non-negative integer n: ");
     scanf("%d", &n);
 
-    // TODO: validate input, call function, print result
+    if (n<0) {
+        printf("Error\n");
+    } else {
+        printf("The result is: %d\n", factorial(n));
+    }
 
     return 0;
 }
diff --git a/src/lab2_3 b/src/lab2_3
new file mode 100755
index 0000000..e5b3571
Binary files /dev/null and b/src/lab2_3 differ
diff --git a/src/lab2_3.c b/src/lab2_3.c
index ddc8af6..bc5f577 100644
--- a/src/lab2_3.c
+++ b/src/lab2_3.c
@@ -12,8 +12,13 @@
 */
 
 int is_prime(int n) {
-    // TODO: check if n is prime using loop up to sqrt(n)
-    return 0; // placeholder
+    if (n<2) return 0;
+    for (int i=2; i*i <= n; i++) {
+        if (n % i == 0) {
+            return 0;
+        }
+    }
+    return 1; // placeholder
 }
 
 int main(void) {
@@ -22,7 +27,17 @@ int main(void) {
     printf("Enter an integer n (>= 2): ");
     scanf("%d", &n);
 
-    // TODO: validate input and print all primes up to n
+    if (n<=2) {
+        printf("Error\n");
+    } else {
+        printf("Prime numbers up to %d:\n", n);
+        for (int i=2; i<=n; i++) {
+            if (is_prime(i)) {
+                printf("%d ", i);
+            }
+        }
+    }
+    printf("\n");
 
     return 0;
 }
diff --git a/src/lab3_task1 b/src/lab3_task1
new file mode 100755
index 0000000..6067f56
Binary files /dev/null and b/src/lab3_task1 differ
diff --git a/src/lab3_task1.c b/src/lab3_task1.c
index f0d73ee..8b444c0 100644
--- a/src/lab3_task1.c
+++ b/src/lab3_task1.c
@@ -23,7 +23,10 @@
 
 #include <stdio.h>
 #include <limits.h>
+<<<<<<< HEAD
+=======
 
+>>>>>>> upstream/main
 // Function prototypes
 int array_min(int arr[], int size);
 int array_max(int arr[], int size);
@@ -44,8 +47,12 @@ int main(void) {
 
 // Implement functions below
 int array_min(int arr[], int size) {
+<<<<<<< HEAD
+    int my_min = INT_MAX;
+=======
     // TODO: return smallest element
     int my_min = INT_MAX; //set to max infinity
+>>>>>>> upstream/main
     for (int i=0;i<size;i++) {
         if (my_min > arr[i]) {
             my_min = arr[i];
@@ -55,16 +62,25 @@ int array_min(int arr[], int size) {
 }
 
 int array_max(int arr[], int size) {
-    // TODO: return largest element
-    return 0; // placeholder
+    int my_max = INT_MIN;
+    for (int i=0;i<size;i++) {
+        if (arr[i] >my_max) {
+            my_max = arr[i];
+        }
+    }
+    return my_max; // placeholder
 }
 
 int array_sum(int arr[], int size) {
-    // TODO: return sum of elements
-    return 0; // placeholder
+    int sum = 0;
+    for (int i=0; i<size; i++) {
+        sum += arr[i];
+    }
+    return sum; // placeholder
 }
 
 float array_avg(int arr[], int size) {
-    // TODO: return average as float
-    return 0.0f; // placeholder
+    if (size == 0) return 0.0f; 
+    int sum = array_sum(arr, size);
+    return (float) sum/size;
 }
diff --git a/src/lab3_task2 b/src/lab3_task2
new file mode 100755
index 0000000..55bbc83
Binary files /dev/null and b/src/lab3_task2 differ
diff --git a/src/lab3_task2.c b/src/lab3_task2.c
index fcc50d8..c0fa430 100644
--- a/src/lab3_task2.c
+++ b/src/lab3_task2.c
@@ -38,9 +38,11 @@ int main(void) {
 
 // Implement functions below
 void swap(int *x, int *y) {
-    // TODO: swap values using a temporary variable
+    int t = *x;
+    *x = *y;
+    *y = t;
 }
 
 void modify_value(int *x) {
-    // TODO: multiply value by 2
+    *x = *x * 2;
 }
diff --git a/src/lab3_task3 b/src/lab3_task3
new file mode 100755
index 0000000..ef8b7c1
Binary files /dev/null and b/src/lab3_task3 differ
diff --git a/src/lab3_task3.c b/src/lab3_task3.c
index 55cc20f..8f4cc79 100644
--- a/src/lab3_task3.c
+++ b/src/lab3_task3.c
@@ -41,10 +41,18 @@ int main(void) {
 
 // Implement functions below
 int my_strlen(const char *str) {
-    // TODO: count characters until '\0'
-    return 0; // placeholder
+    int len = 0;
+    while (str[len] != '\0') {
+        len++;
+    }
+    return len; // placeholder
 }
 
 void my_strcpy(char *dest, const char *src) {
-    // TODO: copy characters until '\0'
+    int i = 0;
+    while (src[i] != '\0') {
+        dest[i] = src[i];
+        i++;
+    }
+    dest[i] = '\0';
 }
diff --git a/src/meow b/src/meow
new file mode 100644
index 0000000..b8613f5
--- /dev/null
+++ b/src/meow
@@ -0,0 +1,3 @@
+Meow meow 1
+Meow meow 2
+Meow meow 3
diff --git a/src/student.txt b/src/student.txt
new file mode 100644
index 0000000..9f934f3
--- /dev/null
+++ b/src/student.txt
@@ -0,0 +1,3 @@
+Alice
+21
+3.75
diff --git a/src/students.txt b/src/students.txt
new file mode 100644
index 0000000..d58f626
--- /dev/null
+++ b/src/students.txt
@@ -0,0 +1,2 @@
+leyli 241 -nan
+db 121 5.80
diff --git a/src/week4_1_dynamic_array b/src/week4_1_dynamic_array
new file mode 100755
index 0000000..8b58b92
Binary files /dev/null and b/src/week4_1_dynamic_array differ
diff --git a/src/week4_1_dynamic_array.c b/src/week4_1_dynamic_array.c
index 575567f..09f950d 100644
--- a/src/week4_1_dynamic_array.c
+++ b/src/week4_1_dynamic_array.c
@@ -1,7 +1,7 @@
 /*
  * week4_1_dynamic_array.c
- * Author: [Your Name]
- * Student ID: [Your ID]
+ * Author: Leyli Iskandarli
+ * Student ID: 241ADB073
  * Description:
  *   Demonstrates creation and usage of a dynamic array using malloc.
  *   Students should allocate memory for an integer array, fill it with data,
@@ -14,6 +14,8 @@
 int main(void) {
     int n;
     int *arr = NULL;
+    int sum = 0;
+    double avg;
 
     printf("Enter number of elements: ");
     if (scanf("%d", &n) != 1 || n <= 0) {
@@ -23,16 +25,29 @@ int main(void) {
 
     // TODO: Allocate memory for n integers using malloc
     // Example: arr = malloc(n * sizeof(int));
+    arr = (int *)malloc(n * sizeof(int));
 
     // TODO: Check allocation success
+    if (arr == NULL) {
+        printf("Error");
+        return 1;
+    }
 
     // TODO: Read n integers from user input and store in array
-
-    // TODO: Compute sum and average
+    //Compute sum and average
+    printf("Enter %d integers: \n", n);
+    for (int i=0; i<n; i++) {
+        scanf("%d", &arr[i]);
+        sum += arr[i];
+    }
+    avg = (double)sum/n;
 
     // TODO: Print the results
+    printf("Sum = %d\n", sum);
+    printf("Average = %.2f\n", avg);
 
     // TODO: Free allocated memory
+    free(arr);
 
     return 0;
 }
diff --git a/src/week4_2_struct_student b/src/week4_2_struct_student
new file mode 100755
index 0000000..f5428fd
Binary files /dev/null and b/src/week4_2_struct_student differ
diff --git a/src/week4_2_struct_student.c b/src/week4_2_struct_student.c
index b04fc32..d379ae5 100644
--- a/src/week4_2_struct_student.c
+++ b/src/week4_2_struct_student.c
@@ -1,7 +1,7 @@
 /*
  * week4_2_struct_student.c
- * Author: [Your Name]
- * Student ID: [Your ID]
+ * Author: Leyli Iskandarli
+ * Student ID: 241ADB073
  * Description:
  *   Demonstrates defining and using a struct in C.
  *   Students should define a 'Student' struct with fields like name, id, and grade.
@@ -13,18 +13,35 @@
 
 // TODO: Define struct Student with fields: name (char[]), id (int), grade (float)
 // Example:
-// struct Student {
-//     char name[50];
-//     int id;
-//     float grade;
-// };
+struct Student {
+    char name[50];
+    int id;
+    float grade;
+};
 
 int main(void) {
     // TODO: Declare one or more Student variables
+    struct Student student1, student2;
 
     // TODO: Assign values (either manually or via scanf)
+    strcpy(student1.name, "Leyli");
+    student1.id = 1;
+    student1.grade = 8.9;
+
+    strcpy(student2.name, "Meow");
+    student2.id = 2;
+    student2.grade = 8.5;
 
     // TODO: Print struct contents using printf
+    printf("Student 1:\n");
+    printf("  Name: %s\n", student1.name);
+    printf("  ID: %d\n", student1.id);
+    printf("  Grade: %.2f\n", student1.grade);
+
+    printf("\nStudent 2:\n");
+    printf("  Name: %s\n", student2.name);
+    printf("  ID: %d\n", student2.id);
+    printf("  Grade: %.2f\n", student2.grade);
 
     return 0;
 }
diff --git a/src/week4_3_struct_database b/src/week4_3_struct_database
new file mode 100755
index 0000000..fb4848d
Binary files /dev/null and b/src/week4_3_struct_database differ
diff --git a/src/week4_3_struct_database.c b/src/week4_3_struct_database.c
index 663b998..e9b299b 100644
--- a/src/week4_3_struct_database.c
+++ b/src/week4_3_struct_database.c
@@ -1,7 +1,7 @@
 /*
  * week4_3_struct_database.c
- * Author: [Your Name]
- * Student ID: [Your ID]
+ * Author: Leyli Iskandarli
+ * Student ID: 241ADB073
  * Description:
  *   Simple in-memory "database" using an array of structs.
  *   Students will use malloc to allocate space for multiple Student records,
@@ -13,6 +13,11 @@
 #include <string.h>
 
 // TODO: Define struct Student with fields name, id, grade
+struct Student {
+    char name[50];
+    int id;
+    float grade;
+};
 
 int main(void) {
     int n;
@@ -25,14 +30,43 @@ int main(void) {
     }
 
     // TODO: Allocate memory for n Student structs using malloc
+    students = (struct Student *)malloc(n * sizeof(struct Student));
+    if (students == NULL) {
+        printf("Error");
+        return 1;
+    }
 
     // TODO: Read student data in a loop
+    for (int i = 0; i < n; i++) {
+        printf("\nEnter data for student %d:\n", i + 1);
+        printf("  Name: ");
+        scanf(" %[^\n]", students[i].name);  
+
+        printf("  ID: ");
+        scanf("%d", &students[i].id);
+
+        printf("  Grade: ");
+        scanf("%f", &students[i].grade);
+    }
 
     // TODO: Display all student records in formatted output
+    printf("\n Student Records: \n");
+    for (int i = 0; i < n; i++) {
+        printf("Student %d:\n", i + 1);
+        printf("Name: %s\n", students[i].name);
+        printf("ID: %d\n", students[i].id);
+        printf("Grade: %.2f\n\n", students[i].grade);
+    }
 
     // Optional: Compute average grade or find top student
+    float sum = 0.0;
+    for (int i = 0; i < n; i++) {
+        sum += students[i].grade;
+    }
+    printf("Average grade: %.2f\n", sum / n);
 
     // TODO: Free allocated memory
+    free(students);
 
     return 0;
 }
diff --git a/src/week5_task1_file_io b/src/week5_task1_file_io
new file mode 100755
index 0000000..1c9c605
Binary files /dev/null and b/src/week5_task1_file_io differ
diff --git a/src/week5_task1_file_io.c b/src/week5_task1_file_io.c
index 336e21a..741020a 100644
--- a/src/week5_task1_file_io.c
+++ b/src/week5_task1_file_io.c
@@ -1,3 +1,5 @@
+//Leyli Iskandarli 241ADB073
+
 // week5_task1_file_io.c
 // Task 1: Read and write data from text files
 // Week 5 – Files & Modular Programming
@@ -8,20 +10,49 @@
 
 int main(void) {
     FILE *fp;
-    char filename[100] = "data.txt";
+    char filename[100];
     char line[256];
+    int line_count = 0;
+
+    // BONUS: ask user for filename instead of using default "data.txt"
+    printf("Enter filename: ");
+    scanf("%s", filename);
 
     // TODO: 1. Open file for writing (mode = "w")
+    fp = fopen(filename, "w");
+
     // TODO: 2. Check if file opened successfully
+    if (fp == NULL) {
+        printf("Error\n");
+        return 1;
+    }
+
     // TODO: 3. Write 2–3 lines of text to the file using fprintf()
+    fprintf(fp, "Meow meow 1\n");
+    fprintf(fp, "Meow meow 2\n");
+    fprintf(fp, "Meow meow 3\n");
+
     // TODO: 4. Close the file
+    fclose(fp);
 
     // TODO: 5. Open file again for reading (mode = "r")
+    fp = fopen(filename, "r");
+    if (fp == NULL) {
+        printf("Error\n");
+        return 1;
+    }
+
     // TODO: 6. Use fgets() in a loop to read and print each line to the console
-    // TODO: 7. Close the file
+    while (fgets(line, sizeof(line), fp) != NULL) {
+        printf("%s", line);
+        line_count++;
+    }
 
-    // BONUS: ask user for filename instead of using default "data.txt"
+    // TODO: 7. Close the file
+    fclose(fp);
+    
     // BONUS: count number of lines read
+    printf("\nNumber of lines: %d\n", line_count);
 
     return 0;
 }
diff --git a/src/week5_task2_struct_save_load b/src/week5_task2_struct_save_load
new file mode 100755
index 0000000..f34cb0b
Binary files /dev/null and b/src/week5_task2_struct_save_load differ
diff --git a/src/week5_task2_struct_save_load.c b/src/week5_task2_struct_save_load.c
index 267dc11..ef636ea 100644
--- a/src/week5_task2_struct_save_load.c
+++ b/src/week5_task2_struct_save_load.c
@@ -1,3 +1,5 @@
+//Leyli Iskandarli 241ADB073
+
 // week5_task2_struct_save_load.c
 // Task 2: Save and load structured records from a file
 // Week 5 – Files & Modular Programming
@@ -28,8 +30,14 @@ int main(void) {
     const char *filename = "student.txt";
 
     // TODO: Call save_student() to save student data to file
+    save_student(s1, filename);
     // TODO: Call load_student() to read data back into a new struct
+    Student loaded = load_student(filename);
     // TODO: Print loaded data to confirm correctness
+    printf("Loaded data:\n");
+    printf("Name: %s\n", loaded.name);
+    printf("Age: %d\n", loaded.age);
+    printf("GPA: %.2f\n", loaded.gpa);
 
     return 0;
 }
@@ -37,13 +45,30 @@ int main(void) {
 // TODO: Implement save_student()
 // Open file for writing, check errors, write fields, then close file
 void save_student(Student s, const char *filename) {
-    // ...
+    FILE *fp = fopen(filename, "w");
+    if (fp == NULL) {
+        printf("Error \n");
+        exit(1);
+    }
+
+    fprintf(fp, "%s\n%d\n%.2f\n", s.name, s.age, s.gpa);
+    fclose(fp);
 }
 
 // TODO: Implement load_student()
 // Open file for reading, check errors, read fields, then close file
 Student load_student(const char *filename) {
     Student s;
-    // ...
+    FILE *fp = fopen(filename, "r");
+    if (fp == NULL) {
+        printf("Error \n");
+        exit(1);
+    }
+
+    fscanf(fp, "%s", s.name);
+    fscanf(fp, "%d", &s.age);
+    fscanf(fp, "%f", &s.gpa);
+
+    fclose(fp);
     return s;
 }
diff --git a/src/week5_task3_student_management_system b/src/week5_task3_student_management_system
new file mode 100755
index 0000000..fb01587
Binary files /dev/null and b/src/week5_task3_student_management_system differ
diff --git a/src/week5_task3_student_management_system.c b/src/week5_task3_student_management_system.c
index 6ed6dfd..f33096f 100644
--- a/src/week5_task3_student_management_system.c
+++ b/src/week5_task3_student_management_system.c
@@ -1,3 +1,5 @@
+//Leyli Iskandarli 241ADB073
+
 // week5_task3_student_management_system.c
 // Task 3: Mini-project – Student management system with file persistence
 // Week 5 – Files & Modular Programming
@@ -29,7 +31,7 @@ int main(void) {
     int choice;
 
     // TODO: Load existing data from file using load_students()
-
+    count = load_students(students);
     do {
         printf("\n=== Student Management System ===\n");
         printf("1. List students\n");
@@ -42,12 +44,15 @@ int main(void) {
         switch (choice) {
             case 1:
                 // TODO: Call list_students()
+                list_students(students, count);
                 break;
             case 2:
                 // TODO: Call add_student()
+                add_student(students, &count);
                 break;
             case 3:
                 // TODO: Call save_students() and exit loop
+                save_students(students, count);
                 break;
             default:
                 printf("Invalid option. Try again.\n");
@@ -60,24 +65,67 @@ int main(void) {
 // TODO: Implement load_students()
 // Open DATA_FILE, read records until EOF, return number of records loaded
 int load_students(Student arr[]) {
-    // ...
-    return 0;
+    FILE *fp = fopen(DATA_FILE, "r");
+    int count = 0;
+
+    if (fp == NULL) {
+        printf("Error\n");
+        return 0;
+    }
+
+    while (fscanf(fp, "%s %d %f", arr[count].name, &arr[count].id, &arr[count].gpa) == 3) {
+        count++;
+        if (count >= MAX_STUDENTS) break;
+    }
+
+    fclose(fp);
+    printf("%d records loaded\n", count);
+    return count;
 }
 
 // TODO: Implement save_students()
 // Write all students to DATA_FILE
 void save_students(Student arr[], int count) {
-    // ...
+    FILE *fp = fopen(DATA_FILE, "w");
+    if (fp == NULL) {
+        printf("Error\n");
+        return;
+    }
+
+    for (int i = 0; i < count; i++) {
+        fprintf(fp, "%s %d %.2f\n", arr[i].name, arr[i].id, arr[i].gpa);
+    }
+
+    fclose(fp);
 }
 
 // TODO: Implement add_student()
 // Read input from user and append to array
 void add_student(Student arr[], int *count) {
-    // ...
+    if (*count >= MAX_STUDENTS) {
+        printf("Limit reached.\n");
+        return;
+    }
+
+    Student s;
+    printf("Enter name: ");
+    scanf("%s", s.name);
+
+    printf("Enter ID: ");
+    scanf("%d", &s.id);
+
+    printf("Enter GPA: ");
+    scanf("%f", &s.gpa);
+
+    arr[*count] = s;
+    (*count)++;
 }
 
 // TODO: Implement list_students()
 // Print all students in readable format
 void list_students(Student arr[], int count) {
-    // ...
+    printf("\n%-20s %-10s %-5s\n", "Name", "ID", "GPA");
+    for (int i = 0; i < count; i++) {
+        printf("%-20s %-10d %-5.2f\n", arr[i].name, arr[i].id, arr[i].gpa);
+    }
 }