Code cleaned up and comments added

b-tree.c

@@ -2,101 +2,101 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-#define MAXCHAR 1000
-FILE* file;
+#define MAXCHAR 1000                //maxchar constant equal to 1000
+FILE* file;                         //global variables initialized
 char data[MAXCHAR];
 
-struct node
+struct node                         //node class initialised
 {
 
-	char record [200];
-	char key [50];
+	char record [200];              //record variable stores the whole string of each record from the file
+	char key [50];                  //the rest of the variables store the record variable split up
 	char module [50];
 	char year [50];
 	char semester [50];
-    struct node* left;
-    struct node* right;
+    struct node* left;              //Creates another node and assigns it as left from the current one
+    struct node* right;             //Creates another node and assigns it as right from the current one
 
 };
 
-struct node* createNode(char record [200]){
+struct node* createNode(char record [200]){                  //procedure to create a new node and input values into its variables
  
-    struct node* newNode = malloc(sizeof(struct node));
-    strcpy(newNode->record, record);
+    struct node* newNode = malloc(sizeof(struct node));      //sets space in the memory for the node using malloc
+    strcpy(newNode->record, record);                         //copies whole record parameter into the new node
     char* token = strtok(record, ",");
-    strcpy(newNode->key, token);
+    strcpy(newNode->key, token);                             //splits record and copies parts of it into the class variables
     token = strtok(NULL, ",");
     strcpy(newNode->module, token);
     token = strtok(NULL, ",");
     strcpy(newNode->year, token); 
     token = strtok(NULL, ",");
     strcpy(newNode->semester, token);
-    newNode->left = NULL;
+    newNode->left = NULL;                                    //finally sets the next left and right node to NULL.
     newNode->right = NULL;
     return newNode;
 
 }
 
-struct node* input(struct node* root, char record [200])
+struct node* input(struct node* root, char record [200])    //procedure to input a record into the tree
 {
 
-    if (root == NULL) return createNode(record);
+    if (root == NULL) return createNode(record);            //if the tree is empty then enter into root
 
-    if (strcmp(record, root->record) < 0){
+    if (strcmp(record, root->record) < 0){                  //compares record to existing records in the tree
 
-        root->left  = input(root->left, record);
+        root->left  = input(root->left, record);            //if record is smaller then recurse the procedure with the left leaf
 
     }
-    else if (strcmp(record, root->record) > 0){
+    else if (strcmp(record, root->record) > 0){             //compares record to existing records in the tree
 
-        root->right = input(root->right, record);
+        root->right = input(root->right, record);           //if record is smaller then recurse the procedure with the left leaf
 
     }   
-    return root;
+    return root;                                            //procedure will recurse until an empty root is found
 
 }
 
-void traverse_order(struct node* root){
+void traverse_order(struct node* root){                                     //procedure to read the tree in incrementing order
 
     if(root == NULL) return;                                                
-    traverse_order(root->left);
-    printf("%s (Left: ", root->key);
+    traverse_order(root->left);                                             //recurses to the last left leaf where its null
+    printf("%s (Left: ", root->key);                                        //printing left-node-right
 
-    if (root->left != NULL) printf("%s)", root->left->key);
+    if (root->left != NULL) printf("%s)", root->left->key);                 //prints out the left and right node keys, else prints null
     else  printf("NULL)");
 
     if (root->right != NULL) printf(" (Right: %s)\n", root->right->key);
     else printf(" (Right: NULL)\n");
 
   	fflush(stdout);
-    fputs(root->record, file);
-    traverse_order(root->right);
+    fputs(root->record, file);                                              //write the record to the file sorted
+    traverse_order(root->right);                                            //recurses to the right node
     
 }
 		
-int main() {
+int main() {                                                                //program begins
 
-    char* filenameread = "pg03data.txt";
+    char* filenameread = "pg03data.txt";                                    //local variables (file paths, counters, tree root, file)
     char* filenamewrite ="pg03sorted.txt";
     int counter = 1;
  	struct node *root = NULL;
     file = fopen(filenameread, "r");
     if (file == NULL) printf("Could not open read file %s", filenameread);
-    while (fgets(data, MAXCHAR, file) != NULL){
+    while (fgets(data, MAXCHAR, file) != NULL){                             //reading records from the file
 
         if (counter == 1){
 
-        	root = input(root, data);
+        	root = input(root, data);                                       //inputs root into the file
         	counter = counter + 1;
 
-        }else input(root,data);
+        }else input(root,data);                                             //inputs the rest of the records as normal
 
    	}
-    fclose(file);
-    file= fopen(filenamewrite, "w");
+    fclose(file);                                                           //read file closes
+    file= fopen(filenamewrite, "w");                                        //opens file to write to
     if (file == NULL) printf("Could not open file to write to %s", filenamewrite);
-    traverse_order(root);
+    traverse_order(root);                                                   //starts the read through the binary tree
     fclose(file);
-    return 0;
+    return 0;                                                               //end of program
 
 }
\ No newline at end of file