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The truth table of XOR, shown in two different ways But just saying what it is doesn’t give a good intuition for what things it’s useful for, or when to use it. So in the next few sections I’ll present a few different ways of thinking about what XOR does. For such a simple operation, it’s possible to describe what it does in a lot of quite different-looking ways. But all of them are true at once!

PuTTY vulnerability vuln-p521-bias Home | FAQ | Feedback | Licence | Updates | Mirrors | Keys | Links | Team Download: Stable · Snapshot | Docs | Privacy | Changes | Wishlist summary: NIST P521 private keys are exposed by biased signature generation class: vulnerability: This is a security vulnerability. priority: high: This should be fixed in the next release. absent-in: 0.67 present-in: 0.68 0.6

[Simon Tatham, initial version 2023-09-01, last updated 2025-03-25] [Coroutines trilogy: C preprocessor | C++20 native | general philosophy ] Introduction Why I’m so enthusiastic about coroutines The objective view: what makes them useful? Versus explicit state machines Versus conventional threads The subjective view: why do I like them so much? “Teach the student when the student is ready” They s

PuTTY vulnerability vuln-indirect-dll-hijack-2 Home | FAQ | Feedback | Licence | Updates | Mirrors | Keys | Links | Team Download: Stable · Snapshot | Docs | Privacy | Changes | Wishlist summary: Further potential malicious code execution via indirect DLL hijacking class: vulnerability: This is a security vulnerability. difficulty: fun: Just needs tuits, and not many of them. priority: high: This

PuTTY vulnerability vuln-ech-overflow Home | FAQ | Feedback | Licence | Updates | Mirrors | Keys | Links | Team Download: Stable · Snapshot | Docs | Privacy | Changes | Wishlist summary: Vulnerability: integer overflow and buffer underrun in terminal emulator's ECH handling class: vulnerability: This is a security vulnerability. difficulty: fun: Just needs tuits, and not many of them. priority: hi

by Simon Tatham 1. Introduction This article attempts to give a sort of ‘orientation tour’ for people whose previous programming background is in high (ish) level languages such as Java or Python, and who now find that they need or want to learn C. C is quite different, at a fundamental level, from languages like Java and Python. However, well-known books on C (such as the venerable Kernighan & Ri

by Simon Tatham This article describes a technique for using the C preprocessor to implement a form of metaprogramming in C, allowing a programmer to define custom looping and control constructions which behave syntactically like C's own for, while and if but manage control flow in a user-defined way. The technique is almost all portable C89, except that some constructions need the feature (availa

作者：Simon Tatham, 職業プログラマ兼、フリーソフトウェアのプログラマ [ English | Português | 简体中文 | Česky | Dansk | Deutsch | Español | Français | Magyar | Italiano | 日本語 | Nederlands | Polski | Русский | 繁體中文 ] はじめに おおやけに利用されるソフトウェアを書いたことがある人なら、おそらく一通は質の悪いバグ報告を受け取ったことがあるだろう。何も言わんとしない報告(「動きません!」)、意味をなさない報告、十分な情報を供さない報告、誤った情報を含む報告などだ。なかには、使用法の誤り、他のプログラムの欠陥、ネットワークの障害などに起因する問題の報告まである。 技術サポートがぞっとする仕事とみなされるには理由があり、その理由こそが質の悪いバグ報

Tweak is a hex editor. It allows you to edit a file at very low level, letting you see the full and exact binary contents of the file. It can be useful for modifying binary files such as executables, editing disk or CD images, debugging programs that generate binary file formats incorrectly, and many other things. Tweak currently runs on Unix, using the ncurses library to run in a terminal. Why ye

Simon Tatham's Home Page Welcome to my web site. I'm Simon Tatham, a software engineer and free-software author in Cambridge, UK. Here are links to the various other pages of this site. About me: some idea of who I am. Free software I've written, which you can download. PuTTY: an SSH client for Windows, also able to talk to serial ports and speak older insecure protocols like Telnet. A collection

Simon Tatham's Portable Puzzle Collection Introduction This page contains a collection of small computer programs which implement one-player puzzle games. All of them run natively on Unix (GTK) and on Windows. They can also be played on the web, as Java or Javascript applets. 2023-09-20: I'm sorry to say that I'm no longer going to be able to build the MacOS version of these puzzles. My Mac was ve

PuTTY FAQ Home | FAQ | Feedback | Licence | Updates | Mirrors | Keys | Links | Team Download: Stable · Snapshot | Docs | Privacy | Changes | Wishlist Appendix A: PuTTY FAQ A.1 Introduction A.1.1 What is PuTTY? A.2 Features supported in PuTTY A.2.1 Does PuTTY support SSH-2? A.2.2 Does PuTTY support reading OpenSSH or ssh.com SSH-2 private key files? A.2.3 Does PuTTY support SSH-1? A.2.4 Does PuTTY

by Simon Tatham, professional and free-software programmer [ English | Português | 简体中文 | Česky | Dansk | Deutsch | Español | Français | Magyar | Italiano | 日本語 | Nederlands | Polski | Русский | 繁體中文 ] Introduction Anybody who has written software for public use will probably have received at least one bad bug report. Reports that say nothing ("It doesn't work!"); reports that make no sense; repor