diff --git a/README.md b/README.md
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+++ b/README.md
@@ -13,6 +13,111 @@ must load and execute the script file called myscript.ba
 
 ## Data Structures
 
+### BigInt
+
+#### BigIntNode struct
+
+```c
+typedef struct bigintNode{
+    long long number;
+    struct bigintNode* next;
+    struct bigintNode* prev;
+}BigIntNode;
+```
+
+#### BigInt Struct
+
+```c
+typedef struct bigIntStruct{
+    bool isNegative;
+    BigIntNode* root;
+unsigned long long size;
+}BigInt;
+```
+
+These two structs keeps BigInts(large numbers). There is no upper or lower limit for numbers
+(other than your computers memory).
+
+Nodes are store maximum 10 digits (lower than 10^10). After 10 digits, another node added to linked list and
+extra digits stored there.
+
+#### BigInt Functions
+
+* ```c 
+  void addBigInt(BigInt* dest, BigInt* number);
+  ```
+  * Sums two BigInts.
+
+* ```c 
+  void subBigInt(BigInt* dest, BigInt* number);
+  ```
+  * Subtracts two BigInts.
+
+* ```c 
+  void addbi_internal(BigInt* dest, BigInt* number);
+  ```
+  * Sums two BigInts without signs.
+
+* ```c 
+  void subbi_internal(BigInt* dest, BigInt* number);
+  ```
+  * Subtracts two BigInts without signs.
+
+* ```c 
+  void tidyBigInt(BigInt* number);
+  ```
+  * Cleans unnecessary nodes from BigInt.
+
+* ```c 
+  int compare(BigInt* num1, BigInt* num2);
+  ```
+  * Compares two BigInts.
+
+* ```c 
+  int compareAbsVal(BigInt* num1, BigInt* num2);
+  ```
+  * Compares two BigInts absolute values.
+
+* ```c 
+  int compareNode(BigIntNode *node1, BigIntNode *node2);
+  ```
+  * Compares two BigIntNodes.(Including next nodes).
+
+* ```c 
+  BigInt *copyBigInt(BigInt *number);
+  ```
+  * Copies the given BigInt and returns its pointer.
+
+* ```c 
+  BigInt *strtobigInt(char* str);
+  ```
+  * Creates a BigInt according to the str and returns its pointer.
+
+* ```c 
+  void printBigInt(BigInt* number);
+  ```
+  * Prints the given BigInt.
+
+* ```c 
+  void printbigIntNode(BigIntNode* node);
+  ```
+  * Prints the given BigIntNode. (Recuses next nodes)
+
+* ```c 
+  void freeBigInt(BigInt* number);
+  ```
+  * Frees the given BigInt.
+
+* ```c 
+  void freeBigIntNode(BigIntNode* node);
+  ```
+  * Frees the given BigIntNode. (Recuses next nodes)
+
+* ```c 
+  char digitCount(long long num);
+  ```
+  * Returns digit count of the given number.
+
 ### Word
 
 #### Word Struct