Dero Virtual Machine
DVM-BASIC

DVM-BASIC Programming Guide

DVM-BASIC is DERO's smart contract programming language - a blockchain-optimized BASIC variant that's easy to learn yet powerful enough for complex dApps with privacy features.

Source: dvm/ - Virtual Machine implementation

Language Features

  • Line-numbered syntax (like GW-BASIC)
  • Strong typing: Uint64 and String
  • Built-in blockchain functions
  • Privacy-preserving operations
  • Deterministic execution

Quick Start

Function Initialize() Uint64
  10 STORE("owner", SIGNER())
  20 STORE("counter", 0)
  30 RETURN 0
End Function

Function Increment() Uint64
  10 DIM current as Uint64
  20 LET current = LOAD("counter")
  30 STORE("counter", current + 1)
  40 RETURN 0
End Function

Data Types & Variables

TypeRangeDefaultUsage
Uint640 to 18,446,744,073,709,551,6150Numbers, balances, counts
StringVariable (size limits apply)""Text, addresses, keys

Declare variables:

10 DIM counter as Uint64
20 DIM name, symbol as String

Operators

TypeOperators
Arithmetic+ - * / %
Bitwise& | ^ ! >> <<
Comparison> >= < <= == !=
String+ (concat), ==, !=

Control Flow

IF-THEN-ELSE:

10 IF value > 100 THEN GOTO 30 ELSE GOTO 50

Loops with GOTO:

10 LET counter = 0
20 LET counter = counter + 1
30 IF counter < 10 THEN GOTO 20

Comments

' Single-line comment
// Alternative single-line
/* Multi-line
   comment */

Functions

Syntax:

Function Name(param1 Type, param2 Type) ReturnType
  10 RETURN value
End Function

Visibility:

  • Uppercase first letter → Public (callable externally)
  • Lowercase first letter → Private (internal only)

Return values:

  • 0 = success
  • Non-zero = error code

Blockchain Functions

State Management

FunctionPurpose
STORE(key, value)Save to blockchain state
LOAD(key)Read from blockchain state
EXISTS(key)Check if key exists

Identity & Transaction

FunctionPurpose
SIGNER()Get transaction sender address
TXID()Get current transaction ID
ADDRESS_RAW(string)Convert address string to raw format
IS_ADDRESS_VALID(string)Validate address format

Asset Operations

FunctionPurpose
SEND_DERO_TO_ADDRESS(addr, amount)Transfer DERO
SEND_ASSET_TO_ADDRESS(addr, amount, scid)Transfer asset/token
DEROVALUE()Get DERO sent in transaction
ASSETVALUE(scid)Get asset sent in transaction

Blockchain Info

FunctionPurpose
BLOCK_HEIGHT()Current block height
BLOCK_TIMESTAMP()Current block timestamp
SCID()This contract's ID

Cryptographic

FunctionPurpose
SHA256(data)Compute SHA256 hash
KECCAK256(data)Compute Keccak256 hash

Best Practices

  1. Security - Always validate inputs and permissions
  2. Gas efficiency - Minimize STORE/LOAD operations
  3. Line spacing - Use increments of 10 for future insertions
  4. Error codes - Return meaningful error codes
  5. Testing - Use Simulator before deployment

Example: Token Contract

Function Initialize() Uint64
  10 STORE("owner", SIGNER())
  20 STORE("supply", 1000000)
  30 STORE("balance:" + SIGNER(), 1000000)
  40 RETURN 0
End Function

Function Transfer(to String, amount Uint64) Uint64
  10 DIM sender as String
  20 DIM sender_bal, recipient_bal as Uint64
  
  30 LET sender = SIGNER()
  40 IF IS_ADDRESS_VALID(to) != 1 THEN GOTO 200
  50 IF amount <= 0 THEN GOTO 200
  
  60 LET sender_bal = LOAD("balance:" + sender)
  70 IF sender_bal < amount THEN GOTO 200
  
  80 IF EXISTS("balance:" + to) THEN GOTO 100
  90 STORE("balance:" + to, 0)
  
  100 LET recipient_bal = LOAD("balance:" + to)
  110 STORE("balance:" + sender, sender_bal - amount)
  120 STORE("balance:" + to, recipient_bal + amount)
  130 RETURN 0
  
  200 RETURN 1 ' Error
End Function

Function BalanceOf(address String) Uint64
  10 IF EXISTS("balance:" + ADDRESS_RAW(address)) THEN GOTO 30
  20 RETURN 0
  30 RETURN LOAD("balance:" + ADDRESS_RAW(address))
End Function

Learn More

Tip: The DVM-BASIC language evolves with DERO. Check official docs for updates!

Related Pages

Smart Contract Examples:

Understanding the DVM:

Deploy & Test: