Fundamentals on Artur Rios Lab

String Similarity: Levenshtein, Jaro and Jaro–Winkler

Wed, 21 Oct 2026 20:00:00 +0000

Two strings are equal or they are not, and for a computer that is the end of it: "Smith" and "Smyth" differ, and so do "recieve" and "receive". For the person who typed them, though, they are almost the same, and a lot of software has to act on that “almost”. A spell checker has to find the word that was meant. A search box has to forgive a typo. A company merging two customer lists has to notice that “Jon Smyth, 12 Main St” and “John Smith, 12 Main Street” are probably the same person. A string similarity measure puts a number on how close two strings are, so a program can make those calls.

What Is a Unit Test? Where Unit Testing Came From and How to Write Good Ones

Tue, 20 Oct 2026 22:30:00 +0000

You change one line in a pricing function and want to know whether anything broke. You could start the whole application, log in, fill a cart and look at the total, for every kind of cart you can think of. Or you could run a few hundred small programs that each call the pricing function with one input and check the answer, and know in under a second. Those small programs are unit tests, and the second way of working is one of the biggest changes in how software has been written in the last thirty years: from testing as a phase at the end of a project, done by someone else, to testing as something every programmer does every few minutes.

How Do Programs Talk to Each Other? JSON, XML, Protobuf, RPC, REST, gRPC, GraphQL and Messaging

Tue, 20 Oct 2026 20:00:00 +0000

A mobile app asks a server for a user’s orders. The server asks a payment service whether an order was paid, tells a warehouse system to ship it, and announces to anyone interested that it has shipped. A code editor asks a language server where a function is defined; an AI agent asks a tool to read a file. All of these are programs talking to other programs, and every one of those conversations rests on two decisions: how the data is encoded into bytes, and how the conversation is shaped, as a function call, a request for a resource, a query, a stream or a message dropped in a queue.

How Do Computer Networks Work? TCP/IP, the OSI Model and the Protocols Every Programmer Uses

Tue, 20 Oct 2026 18:00:00 +0000

Very few programs work alone. A web page fetches data from an API, the API queries a database on another machine, the database replicates to a third, and all of them ask a time server what time it is and a name server where everyone else lives. Every one of those conversations crosses a network, and every one of them can be slow, fail halfway or arrive in pieces. A programmer who understands what happens between connect() and the reply can tell a DNS problem from a TLS problem from a congested link, and can write code that copes with all three.

How Does a Web Browser Work? From a URL to Pixels on the Screen

Tue, 20 Oct 2026 17:30:00 +0000

A web browser is probably the most complex program most people use every day. In a few hundred milliseconds it turns a line of text in an address bar into a network connection, a stream of bytes, a tree of objects, a set of styled and measured boxes, and finally pixels, then keeps all of that live while scripts change it and the user scrolls, types and clicks. It is also a small operating system in its own right (What Is an Operating System?), running untrusted code from every site you visit and keeping those sites apart.

What Is Text Encoding? From Telegraph Codes to Unicode and UTF-8

Tue, 20 Oct 2026 17:00:00 +0000

A computer stores nothing but numbers. Every letter you read on a screen, every name in a database and every line of source code is held as a sequence of numbers, and something has to agree on which number means which character. That agreement is a text encoding. When it works, nobody notices. When two programs disagree, “café” turns into “cafÃ©”, a customer’s name is rejected as invalid, or an emoji crashes a database insert. This article explains what a text encoding is, how the world got from telegraph codes to Unicode, how the modern encodings work bit by bit, and where text still goes wrong. The examples were run with Python 3.10 and Node.js 12, and their output is shown as printed.

What Are Data Structures? From Arrays to Hash Tables, and How to Choose One

Tue, 20 Oct 2026 16:30:00 +0000

Niklaus Wirth titled a 1976 book Algorithms + Data Structures = Programs,¹ and What Is Programming? quoted it: choosing how to represent information is as much a part of programming as choosing the steps that work on it. This article is about the second half of that equation. It explains what a data structure is, where the classic ones came from, how each works and what it costs, and how to choose between them. The examples were run with Python 3.10 on an Intel Core i9-13900K, and their output is shown exactly as printed.

What Is a Compiler? How Source Code Becomes a Running Program

Tue, 20 Oct 2026 16:00:00 +0000

What Is Programming? ended with high-level languages taking over from machine code, and What Is a Processor? described the machine instructions a CPU actually runs. Between the two sits the compiler: the program that turns one into the other. This article explains what a compiler is, where compilers came from, how each of their phases works, how a C file becomes an executable on a real system, and how to build a small compiler of your own. Every compiler output shown here was produced by running the tools on Ubuntu 22.04 with GCC 11.4 and Python 3.10, not written by hand.

Processes and Threads: What They Are, Where They Came From and How They Work

Tue, 20 Oct 2026 15:30:00 +0000

What Is an Operating System? introduced processes and threads in a few paragraphs, and What Is a Processor? showed the hardware they run on. This article gives them the space they deserve. Almost every question about how a program behaves when it does more than one thing at a time, from “why did my server run out of memory?” to “why does this counter come out wrong?”, comes down to the difference between a process and a thread.

What Is a Processor? History, Architectures and How a CPU Works

Tue, 20 Oct 2026 15:00:00 +0000

What Is Programming? described programs as precise descriptions of a process, and What Is an Operating System? described the software that shares a machine between them. This article goes one level further down, to the part that does the work: the processor. It covers what a processor is, how it got from vacuum tubes to tens of billions of transistors, the main ways processors are designed, and, in some detail, how a modern CPU turns instructions into results.

What Is an Operating System? History, Architectures and How It Works

Tue, 20 Oct 2026 09:00:00 +0000

Every program you have ever written leaned on an operating system without asking. Printing a line, opening a file, allocating memory, waiting for a key press: none of these is something a processor knows how to do. The operating system does them on the program’s behalf, and does them for hundreds of other programs at the same time without letting any of them trample the others.

What Is Programming? followed the history of telling machines what to do. This article follows the program that stands between every other program and the machine: what it is, how it came to exist, the main ways it can be built, and, in some detail, how it actually works.

What Is Programming? A Short History of Telling Machines What to Do

Mon, 19 Oct 2026 09:00:00 +0000

Ask ten developers what programming is and you will get ten answers: “writing code”, “solving problems”, “telling a computer what to do”. All of them are true, and none of them is quite enough. This article tries to pin the idea down, and then follows it through roughly two centuries of history — because most of what feels arbitrary about programming today makes sense once you know where it came from.