A 108-byte contract deployed by the Ethereum Foundation wallet on September 20, 2015. Written in Solidity v0.1.4, it implements bar(uint256) returning x + 2. De
Historical Significance
Completes the earliest known ABI compliance test suite on Ethereum mainnet. Tests calldata input encoding and arithmetic return values. The EF1 wallet called bar(0) just 3 hours after deployment to verify.
Context
Deployed 52 days after Frontier launch. Three contracts deployed in one session: constant return, address return, and computed input return. A systematic ABI test harness executed on mainnet.
Key Facts
Description
EF1 ABI Test Suite
On September 20, 2015, the Ethereum Foundation wallet 0x5eD8Cee6b63b1c6AFce3AD7c92f4fD7E1B8fAd9F deployed three ABI test contracts in a 6-hour window:
| Time (UTC) | Address | Function | Returns |
|---|---|---|---|
| 06:28 | 0xe30608b5 | foo() | uint256(5) |
| 08:48 | 0xdf8eb001 | foo() | address |
| 09:35 | 0x441e72c6 | bar(uint256) | x + 2 |
bar(uint256) (selector 0x0423a132) takes an integer and returns it plus 2. Unlike the other two, this tests calldata input handling -- the most complete ABI test of the three.
The EF1 wallet called bar(0) at 12:39 UTC, 3 hours after deployment, confirming active testing.
Compilation note: Named return variable required -- function bar(uint256 x) returns (uint256 result) compiles to different bytecode than the anonymous variant. Cracked in 2026 with soljson v0.1.4, optimizer off.
Together these three contracts are among the earliest evidence of systematic ABI testing on Ethereum mainnet.
Source Verified
Exact bytecode match. 108 bytes. Named return variable required: returns (uint256 result) with result = x + 2.
Heuristic Analysis
The following characteristics were detected through bytecode analysis and may not be accurate.
Frontier Era
The initial release of Ethereum. A bare-bones implementation for technical users.
Bytecode Overview
Verified Source Available
Source verified through compiler archaeology and exact bytecode matching.
View Verification ProofShow source code (Solidity)
contract C {
function bar(uint256 x) returns (uint256 result) {
result = x + 2;
}
}