{"id":371,"date":"2024-06-28T12:37:43","date_gmt":"2024-06-28T12:37:43","guid":{"rendered":"https:\/\/study.madeeasy.in\/?p=371"},"modified":"2025-07-16T14:43:26","modified_gmt":"2025-07-16T09:13:26","slug":"what-is-system-call-in-operating-system-os","status":"publish","type":"post","link":"https:\/\/www.madeeasy.in\/study\/cs-it\/operating-system\/what-is-system-call-in-operating-system-os","title":{"rendered":"What is System Call?"},"content":{"rendered":"\r\n<p style=\"text-align: justify;\">System call provides the services of operating system to the user programs via Application Program Interface (API). It provides an interface between a process and operating system to allow user level processes to request services of operating system.<\/p>\r\n<h2 style=\"text-align: justify;\">WHAT IS PROCESS?<\/h2>\r\n<p style=\"text-align: justify;\">A process is an activity of executing a program. It is a program under execution. Every process needs certain resources to complete its task.<\/p>\r\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-207 aligncenter\" src=\"http:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/06\/abstraction-view-of-a-process.png\" alt=\"Abstraction view of a process\" width=\"182\" height=\"195\" \/><\/p>\r\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_79_1 ez-toc-wrap-left counter-hierarchy ez-toc-counter ez-toc-light-blue ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.madeeasy.in\/study\/cs-it\/operating-system\/what-is-system-call-in-operating-system-os\/#Process-Control-Block-PCB\" >Process Control Block (PCB)<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.madeeasy.in\/study\/cs-it\/operating-system\/what-is-system-call-in-operating-system-os\/#PROCESS-STATE-MODELS\" >PROCESS STATE MODELS<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.madeeasy.in\/study\/cs-it\/operating-system\/what-is-system-call-in-operating-system-os\/#SCHEDULING\" >SCHEDULING<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.madeeasy.in\/study\/cs-it\/operating-system\/what-is-system-call-in-operating-system-os\/#Long-term-Scheduler\" >Long-term Scheduler<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.madeeasy.in\/study\/cs-it\/operating-system\/what-is-system-call-in-operating-system-os\/#Medium-term-Scheduler\" >Medium-term Scheduler<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.madeeasy.in\/study\/cs-it\/operating-system\/what-is-system-call-in-operating-system-os\/#Short-term-Scheduler\" >Short-term Scheduler<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.madeeasy.in\/study\/cs-it\/operating-system\/what-is-system-call-in-operating-system-os\/#Dispatcher\" >Dispatcher<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Process-Control-Block-PCB\"><\/span>Process Control Block (PCB)<span class=\"ez-toc-section-end\"><\/span><\/h3>\r\n<p style=\"text-align: justify;\">A process control block is a data structure maintained by the operating system for every process. The PCB is identified by an integer process ID (PID). A PCB keeps all the information needed to keep track of a process as listed below:<\/p>\r\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-208 aligncenter\" src=\"http:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/06\/process-control-block.png\" alt=\"Process control block\" width=\"182\" height=\"189\" \/><\/p>\r\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"PROCESS-STATE-MODELS\"><\/span>PROCESS STATE MODELS<span class=\"ez-toc-section-end\"><\/span><\/h3>\r\n<p style=\"text-align: justify;\">Process state defines the current activity of the process. Process states are: new, running, ready, blocked, suspended (suspended ready, suspended blocked), etc.<\/p>\r\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-209 aligncenter\" src=\"http:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/06\/process-state-models.png\" alt=\"Process state models\" width=\"448\" height=\"331\" \/><\/p>\r\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"SCHEDULING\"><\/span>SCHEDULING<span class=\"ez-toc-section-end\"><\/span><\/h3>\r\n<p style=\"text-align: justify;\">Scheduling depends on three scheduler in the system<\/p>\r\n<ol style=\"text-align: justify;\">\r\n<li>Long-term scheduler<\/li>\r\n<li>Medium-term scheduler<\/li>\r\n<li>Short-term scheduler<\/li>\r\n<\/ol>\r\n<h4 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Long-term-Scheduler\"><\/span>Long-term Scheduler<span class=\"ez-toc-section-end\"><\/span><\/h4>\r\n<ul style=\"text-align: justify;\">\r\n<li>It determines which process are to be admitted to the system for processing. It selects processes from the queue (from disk) and leads them into memory for execution.<\/li>\r\n<\/ul>\r\n<h4 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Medium-term-Scheduler\"><\/span>Medium-term Scheduler<span class=\"ez-toc-section-end\"><\/span><\/h4>\r\n<ul style=\"text-align: justify;\">\r\n<li>The mid term scheduler involves in the decision to swap processes from main memory to secondary memory and vice-versa.<\/li>\r\n<\/ul>\r\n<h4 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Short-term-Scheduler\"><\/span>Short-term Scheduler<span class=\"ez-toc-section-end\"><\/span><\/h4>\r\n<ul style=\"text-align: justify;\">\r\n<li>It selects a process from the ready queue and allocates CPU to one of then, i.e., process state changes from ready to run.<\/li>\r\n<\/ul>\r\n<h4 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Dispatcher\"><\/span>Dispatcher<span class=\"ez-toc-section-end\"><\/span><\/h4>\r\n<p style=\"text-align: justify;\">The dispatcher is the module that gives a process control over the CPU after it has been selected by the short term scheduler.<\/p>\r\n\r\n\r\n\r\n<p style=\"text-align: center;\"><a class=\"btn btn-danger\" role=\"button\" href=\"https:\/\/study.madeeasy.in\/cs-it\/operating-system\/what-is-dual-mode-operation-in-operating-system\/\" target=\"_blank\" rel=\"noopener\">&lt;&lt; Previous<\/a> | <a class=\"btn btn-success\" role=\"button\" href=\"https:\/\/study.madeeasy.in\/cs-it\/operating-system\/what-is-thread-in-operating-system\/\" target=\"_blank\" rel=\"noopener\"> Next &gt;&gt;<\/a> <br \/><strong> Must Read: <\/strong> <a href=\"https:\/\/study.madeeasy.in\/subjects\/what-is-an-operating-system-and-its-types\/\" target=\"_blank\" rel=\"noopener\"><strong>What is an operating system and its types?<\/strong><\/a><\/p>\r\n<p>&nbsp;<\/p>\r\n","protected":false},"excerpt":{"rendered":"<p>System call provides the services of operating system to the user programs via Application Program Interface (API). It provides an<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[94,3],"tags":[100,101,102],"class_list":["post-371","post","type-post","status-publish","format-standard","hentry","category-operating-system","category-cs-it","tag-process-state-models","tag-system-call","tag-what-is-process"],"_links":{"self":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/371","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/comments?post=371"}],"version-history":[{"count":0,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/371\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/media?parent=371"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/categories?post=371"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/tags?post=371"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}