{"id":13893,"date":"2025-09-24T12:26:53","date_gmt":"2025-09-24T11:26:53","guid":{"rendered":"https:\/\/pstqb.pt\/?p=13893"},"modified":"2025-10-23T09:18:41","modified_gmt":"2025-10-23T08:18:41","slug":"therac-25-erro-de-software-deixou-vitimas-ha-40-anos","status":"publish","type":"post","link":"https:\/\/pstqb.pt\/en\/therac-25-erro-de-software-deixou-vitimas-ha-40-anos\/","title":{"rendered":"Therac-25: Software Error Left Victims 40 Years Ago"},"content":{"rendered":"<div data-elementor-type=\"wp-post\" data-elementor-id=\"13893\" class=\"elementor elementor-13893\">\n\t\t\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-6e368fa elementor-section-boxed elementor-section-height-default elementor-section-height-default wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-equal-height-no\" data-id=\"6e368fa\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-8b4cf3a\" data-id=\"8b4cf3a\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-24d535f wpr-stt-btn-align-fixed wpr-stt-btn-align-fixed-right elementor-widget elementor-widget-wpr-back-to-top\" data-id=\"24d535f\" data-element_type=\"widget\" data-widget_type=\"wpr-back-to-top.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<div class=\"wpr-stt-wrapper\"><div class='wpr-stt-btn' data-settings='{&quot;animation&quot;:&quot;fade&quot;,&quot;animationOffset&quot;:&quot;0&quot;,&quot;animationDuration&quot;:&quot;200&quot;,&quot;fixed&quot;:&quot;fixed&quot;,&quot;scrolAnim&quot;:&quot;800&quot;}'><span class=\"wpr-stt-icon\"><i class=\"fas fa-chevron-up\"><\/i><\/span><\/div><\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-b122b8c elementor-widget elementor-widget-text-editor\" data-id=\"b122b8c\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<div><p data-start=\"0\" data-end=\"521\">About 40 years ago, a <em>software<\/em> was primarily responsible for the deaths of patients using the Therac-25, a radiotherapy machine developed to treat cancer. The equipment had two operating modes: electron beam, used to treat superficial tissues such as the skin; and high-energy X-ray beam, designed to target deeper tumors. Unlike previous versions, the Therac-25 was designed with controls via <em>software<\/em>and leaving aside various physical safety protections.<\/p><p data-start=\"523\" data-end=\"1018\">The problem in question was a programming flaw involving a race condition: when the operator entered commands too quickly, the logic of the <em>software<\/em> could skip verification steps and release radiation in a completely uncontrolled manner. As the machine took a few seconds to switch modes, this rapid operation created a dangerous fault, resulting in doses being projected up to 100 times stronger than recommended, leading to severe internal burns and, in several cases, death.<\/p><p data-start=\"1020\" data-end=\"1366\">Between 1985 and 1987, six incidents were documented, three of them fatal. Some of these patients received massive amounts of radiation in a matter of seconds, and ended up dying days later. The case became famous for showing how invisible flaws in the <em>software<\/em> can have devastating consequences when critical systems do not have physical redundancies.<\/p><p data-start=\"1368\" data-end=\"1792\">The Therac-25 disaster served as a milestone in the engineering history of <em>software<\/em> and in the area of medical devices, also leading to important changes in the requirements for testing, documentation and formal validation of programs used in safety-critical contexts.<\/p><\/div><p>The original article via <i>Tom's Hardware<\/i>\u00a0<a href=\"https:\/\/www.tomshardware.com\/software\/notorious-software-bug-was-killing-people-40-years-ago-at-least-three-people-died-after-radiation-doses-that-were-100x-too-strong-from-the-buggy-therac-25-radiation-therapy-machine\">here<\/a>.\u00a0<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>","protected":false},"excerpt":{"rendered":"<p>About 40 years ago, a software error was primarily responsible for the deaths of patients using the Therac-25, a radiotherapy machine developed to treat cancer. The equipment had two operating modes: electron beam, used to treat superficial tissues such as the skin; and high-energy X-ray beam, designed to target deeper tumors. Unlike previous versions, the Therac-25 was designed with software controls, leaving aside various physical safety protections. The problem in question lay in a programming flaw involving a race condition: when the operator entered commands too quickly, the software logic could skip verification steps and release radiation in a completely uncontrolled manner. As the machine took a few seconds to switch modes, this speed of operation created a dangerous flaw, resulting in doses being projected up to 100 times stronger than recommended, leading to severe internal burns and, in several cases, death. Between 1985 and 1987, six incidents were documented, three of them fatal. Some of these patients received massive amounts of radiation in a matter of seconds, and ended up dying days later. The case became famous for showing how invisible software failures can have devastating consequences when critical systems lack physical redundancies. The Therac-25 disaster served as a milestone in the history of software engineering and in the field of medical devices, also leading to important changes in the requirements for testing, documentation and formal validation of programs used in safety-critical contexts. The original article via Tom's Hardware here.\u00a0<\/p>","protected":false},"author":2,"featured_media":13898,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[31],"tags":[],"class_list":["post-13893","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-destaque"],"_links":{"self":[{"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/posts\/13893","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/comments?post=13893"}],"version-history":[{"count":1,"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/posts\/13893\/revisions"}],"predecessor-version":[{"id":13928,"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/posts\/13893\/revisions\/13928"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/media\/13898"}],"wp:attachment":[{"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/media?parent=13893"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/categories?post=13893"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pstqb.pt\/en\/wp-json\/wp\/v2\/tags?post=13893"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}