--- title: cucu: a compiler you can understand (1/3) | daily.dev description: This is the first part of a three-part series building a toy C-like compiler called CUCU, designed to be simple enough to understand. It defines the language... canonical: https://daily.dev/posts/cucu-a-compiler-you-can-understand-1-3--wcenpl1as twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: cucu: a compiler you can understand (1/3) | daily.dev og:description: This is the first part of a three-part series building a toy C-like compiler called CUCU, designed to be simple enough to understand. It defines the language... og:url: https://daily.dev/posts/cucu-a-compiler-you-can-understand-1-3--wcenpl1as og:image: https://api.daily.dev/og/posts/wcENpL1AS.png og:image:alt: cucu: a compiler you can understand (1/3) og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # cucu: a compiler you can understand (1/3) **[zserge's blog](https://daily.dev/sources/zserge)** · 8 min read · 0 upvotes · 0 comments ## Summary This is the first part of a three-part series building a toy C-like compiler called CUCU, designed to be simple enough to understand. It defines the language grammar in EBNF (variable/function declarations, statements, expressions with operator precedence), then implements a lexer in C that tokenizes source input using a single-byte lookahead buffer. Full working lexer source code is included, which tokenizes identifiers, operators, string literals, and comments. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do you write a simple lexer in C that tokenizes identifiers, operators, and string literals? A simple lexer can use a single readtok() function with a one-byte lookahead buffer (nextc) to avoid needing to un-read bytes from the stream. It skips whitespace, then tries to read an identifier (letters, digits, underscore), then operators like &, |, <, >, =, !, then string literals delimited by quotes, then comments, and finally falls back to reading a single byte as a standalone token. _See a full worked example of compiler and lexer fundamentals curated for developers on daily.dev._ ### How does operator precedence get expressed in an EBNF grammar for expressions? Operator precedence is expressed through the nesting order of grammar rules, from lowest precedence at the top to highest at the bottom, with assignment last and parentheses/brackets evaluated first. For example, under this scheme 8>>1+1 evaluates to 2 because right-shift is defined at a lower precedence level than addition, so it behaves as 8>>(1+1) rather than (8>>1)+1. _Developers designing their own mini-languages can find grammar and parsing deep dives like this on daily.dev._ ## Similar posts on daily.dev - [C3](https://daily.dev/posts/c3-5w6a8vyad) · Hacker News · 0 upvotes · 0 comments - [Overengineered calculator: Zig \+ QBE](https://daily.dev/posts/overengineered-calculator-zig-qbe-af2hy5t5q) · Lobsters · 0 upvotes · 0 comments --- Tags: [#c](https://daily.dev/tags/c) [View this post on daily.dev](https://daily.dev/posts/cucu-a-compiler-you-can-understand-1-3--wcenpl1as) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"cucu: a compiler you can understand (1/3)","url":"https://daily.dev/posts/cucu-a-compiler-you-can-understand-1-3--wcenpl1as","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/cucu-a-compiler-you-can-understand-1-3--wcenpl1as"},"datePublished":"2026-08-23T10:20:15.824Z","dateModified":"2026-08-23T10:21:11.843Z","description":"This is the first part of a three-part series building a toy C-like compiler called CUCU, designed to be simple enough to understand. 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