HCODX |

Online Verilog Compiler Runner (Editor, Interpreter)

Full IDE
Select Language
Online Code Compiler
Full HTML IDE
Py main.py
Program Output Ready 
  Welcome to HCODX Online Compiler

  Quick Start:
  Ctrl+Enter  Run code
  Ctrl+S      Save / Download
  Ctrl+L      Clear output

  Select a language and start coding.
✓
Success
Operation completed

Why Use Our Free Verilog?

Online Verilog Compiler with an Interactive Terminal

Compile and run Verilog code online instantly with HCODX. Our free cloud-based Verilog compiler supports real-time execution, standard input, syntax highlighting, and code download. No installation or configuration required. Start coding in Verilog now.

Instant Execution

Run Verilog instantly without installing any IDEs or configuring environments. Our cloud-based Verilog handles libraries, runtimes, and dependencies automatically so you can focus on writing code.

Perfect for Learning

Whether you are studying algorithms in Verilog, practicing data structures in Verilog, or exploring functional programming, our tool provides real-time stdout/stderr feedback with interactive standard input support.

Professional Features

  • Standard Input (stdin) support
  • 85+ programming languages
  • Syntax highlighting with themes
  • Zero-setup cloud environment
  • Download code as .v
  • Real-time compilation & execution

Why developers use HCODX

HCODX is a free online compiler and code runner: write code in your browser, execute it on a cloud sandbox, and interact with your program through a live terminal. Students use it for coursework and interview practice; developers use it to test snippets in 85+ languages without setting up a local environment.

About Verilog

Verilog is the hardware description language behind a huge share of the world's digital chips, and Icarus Verilog is the open source simulator that lets you run it without vendor licenses. Instead of instructions executing in order, you describe registers, wires, and always blocks that respond to clock edges, then drive them from a testbench and observe the waveform of values over simulated time. Icarus (iverilog plus its vvp runtime) is the standard choice in university digital design labs and hobbyist FPGA workflows targeting boards like the iCE40. This page compiles your modules and testbench and streams $display output live in the terminal, so you can debug a counter or ALU design straight from the browser.

Hello World in Verilog

module counter(
    input wire clk,
    input wire rst,
    output reg [3:0] count
);
    always @(posedge clk or posedge rst) begin
        if (rst)
            count <= 4'd0;
        else
            count <= count + 4'd1;
    end
endmodule

module tb;
    reg clk = 0;
    reg rst = 1;
    wire [3:0] count;

    counter uut (.clk(clk), .rst(rst), .count(count));

    always #5 clk = ~clk;

    initial begin
        $display("time | rst count");
        #12 rst = 0;
        repeat (6) begin
            @(posedge clk);
            #1 $display("%4t |  %b  %d", $time, rst, count);
        end
        $display("Counter reached %0d, stopping.", count);
        $finish;
    end
endmodule

When to use Verilog

Icarus Verilog is the workhorse of digital logic coursework: counters, finite state machines, ALUs, and pipeline stages are all assigned as module-plus-testbench pairs exactly like the example above. FPGA hobbyists in the open source toolchain community simulate designs here before synthesizing with yosys, and students preparing for computer engineering exams verify blocking versus nonblocking assignment behavior interactively. It is also convenient for interview preparation at hardware companies, where whiteboard RTL questions can be sanity-checked in seconds without installing a simulator. HCODX is a free online Verilog editor, runner and interpreter — an IDE-grade compiler and playground to write and run code online, execute code with live output and live preview, no downloads or web server required.

Common questions

How do I see my simulation results in the terminal?

Use system tasks in your testbench: $display prints a line immediately, $monitor prints whenever listed signals change, and $time reports simulation time. Output streams live into the terminal as simulation advances. Always end with $finish, otherwise a free-running clock generator keeps the simulation alive until the sandbox time limit stops it.

Which simulator and Verilog standard is used here?

Your code is compiled with Icarus Verilog and executed by its vvp runtime, with solid support for Verilog-2001 and the commonly used parts of Verilog-2005, including generate blocks and named port connections. SystemVerilog support is partial, so classwork written in plain Verilog is the safest fit; advanced SV verification features like classes will not compile.

Can I view waveforms like GTKWave output on this page?

Not graphically; the environment is a text terminal, so the usual workflow of dumping a VCD file with $dumpfile and opening it in GTKWave does not apply. The practical substitute is $monitor, which logs every signal change with timestamps, giving you a textual waveform that is usually sufficient for homework-scale designs.