From 3728acea49328d6b8932275f582b81dcf2356df2 Mon Sep 17 00:00:00 2001
From: mo khan <mo@mokhan.ca>
Date: Mon, 8 Feb 2021 13:33:22 -0700
Subject: descibe system calls and user/kernel mode

---
 doc/assignment1.md | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

(limited to 'doc')

diff --git a/doc/assignment1.md b/doc/assignment1.md
index 539c936..aaf1e0e 100644
--- a/doc/assignment1.md
+++ b/doc/assignment1.md
@@ -255,6 +255,28 @@ Instructions: Please answer the following questions in about 1-2 pages each.
     [source][geeks-von-neumann]
 
 1. Define system call, and list the main types of system calls. Elaborate on how a system call interacts with a standard C library and hardware under a dual-mode operating system environment. (10 marks)
+
+    The two types of systems call modes are kernel mode and user mode.
+    With a mode bit we are able to determine if a task is being executed on behalf o
+    the operating system or the user. A user may request a service from the
+    operating system via a system call. In this case the system call
+    will transition from user mode to kernel mode to perform the request then
+    transition back to user mode once the request has been fulfilled.
+
+    ```plaintext
+    user
+      [process] -> [system call]   [return from system call]
+                       |                   |
+                  (user mode)         (user mode)
+    -------------------V------------------ A-----------------
+    -------------------V------------------ A-----------------
+    kernel             |                   |
+                 (kernel mode)             |
+                       |                   |
+                     [execute system call]-|
+    ```
+
+
 1. Describe the overall structure of virtual machines, and compare VMware and JVM. (15 marks)
 
 # Sources:
-- 
cgit v1.2.3