Compiler

What is a compiler?

A compiler is a program that converts high-level, human-readable code (e.g., C++, Java, Solidity, Vyper) into machine code or bytecode, enabling a computer to execute the instructions.

Some compilers translate code into an intermediate assembly language before generating machine code, while others convert it directly. This process of transforming source code into machine-readable instructions is known as compilation. 

Unlike an interpreter, which executes code line by line, a compiler processes the entire codebase at once, producing an executable file or optimized code for runtime.

How does a compiler work?

A compiler analyzes the source code and breaks it down into individual instructions that a computer can execute. In simple terms, it converts program code into low-level binary instructions (0s and 1s) that the hardware can understand.

‍

The compilation process occurs in several phases, with the output of each step serving as the input for the next. These phases are as follows:

1. Lexical analysis

First, the compiler performs a lexical analysis in which it breaks down the source code into a sequence of tokens. Tokens are the smallest units of code used to represent individual program elements such as keywords, operators, and identifiers. 

2. Syntactic and semantic analysis
Next, the compiler checks the source code for any syntax errors, ensuring it follows the correct language rules. If errors are found, the compilation stops, and the compiler returns an error.

3. Optimization
After parsing and error-checking, the compiler performs low-level optimizations to improve performance. This can include reducing the amount of memory the program uses or reordering instructions for faster execution.

4. Output code generation
Finally, the compiler generates machine code that corresponds to the original source code, creating a binary file that the computer’s hardware can execute directly.

‍

Solidity code example and compiler output

Here’s a simple example of the Solidity code: 

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract HelloWorld {
    string public message;

    constructor() {
        message = "Hello, Blockchain!";
    }
}

‍
The Solidity compiler (solc) translates the source code into Ethereum Virtual Machine (EVM) bytecode. This bytecode is what is deployed and executed on the blockchain.

Here is the deployment bytecode generated by the compiler:

‍

0x608060405234801561000f575f80fd5b5060043610610029575f3560e01c80
63e21f37ce1461002d575b5f80fd5b61003561004b565b604051610042919061
0146565b60405180910390f35b5f805461005790610193565b80601f01602080
9104026020016040519081016040528092919081815260200182805461008390
610193565b80156100ce5780601f106100a55761010080835404028352916020
01916100ce565b820191905f5260205f20905b81548152906001019060200180
83116100b157829003601f168201915b505050505081565b5f81519050919050
565b5f82825260208201905092915050565b8281835e5f83830152505050565b
5f601f19601f8301169050919050565b5f610118826100d6565b610122818561
00e0565b93506101328185602086016100f0565b61013b816100fe565b840191
505092915050565b5f6020820190508181035f83015261015e818461010e565b
905092915050565b7f4e487b7100000000000000000000000000000000000000
0000000000000000005f52602260045260245ffd5b5f60028204905060018216
806101aa57607f821691505b6020821081036101bd576101bc610166565b5b50
91905056fea2646970667358221220133997eb65d20989cd1fa7eded2dd7b3f5
1caaafe0010253b0f02f5024dcfd6d64736f6c634300081a0033

Compilers for blockchain and general programming:

Compilers are essential tools in both general programming and blockchain development, but their roles differ due to the unique needs and challenges of each domain.

‍