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CmSc 335 Operation Systems Homework 01, due 09/07 Solution 1. Problem 1.1. page 37: Suppose the hypothetical processor of Figure 1.3 also has two I/O instructions: 0011 = Load AC from I/O 0111 = Store AC to I/O In these cases, the 12-bit address identifies a particular external device. Show the program execution (using the format of Figure 1.4) for the following program: 1. Load AC from I/O device 5 2. Add contents of memory location 940 3. Store AC to I/O device 6 Assume that the next value retrieved from device 5 is 3, and that location 940 contains a value of 2. #1. Fetch: The instruction at memory location 300 (this is the content of PC) is loaded into IR. This instruction is 3005 (load AC from I/O device 5) Memory 300 3005 301 5940 302 7006 CPU Registers 300 PC AC 3005 IR 940 I/O Device 005 0003 0002 #2. Execute : AC is loaded with the content of I/O device 5. PC is incremented. 300 301 302 Memory 3005 5940 7006 940 0002 CPU Registers 301 PC 0003 AC 3005 IR I/O Device 005 0003 #3. Fetch: The instruction at memory location 301 (this is the content of PC) is loaded into IR. This instruction is 5940 (add AC to the content of location 940) Memory 300 3005 301 5940 302 7006 CPU Registers 301 PC 0003 AC 5940 IR 940 I/O Device 005 0003 0002 #4. Execute: The content of AC is added to the content of location 940. The result is in AC. PC is incremented Memory 300 3005 301 5940 302 7006 CPU Registers 302 PC 0005 AC 5940 IR 940 I/O Device 005 0003 0002 #5. Fetch: The instruction at memory location 302 (this is the content of PC) is loaded into IR. This instruction is 7006 (store AC at I/O device 6) Memory 300 3005 301 5940 302 7006 CPU Registers 302 PC 0005 AC 7006 IR 940 I/O Device 005 0003 0002 #6. Execute: The content of AC is stored into I/O device 6. PC is incremented. 300 301 302 Memory 3005 5940 7006 940 0002 CPU Registers 303 PC 0005 AC 7006 IR I/O Device 005 0003 006 0005 2. Describe the evolution of operating systems (300 – 500 words) See Section 2.2 p.52 3. Read Chapter 2 and give answers to the following questions (Review questions 2.1 and 2.4 on p. 103): a. What are three objectives of an OS design? Convenience: An operating system makes a computer more convenient to use. Efficiency: An operating system allows the computer system resources to be used in an efficient manner. Ability to evolve: An operating system should be constructed in such a way as to permit the effective development, testing, and introduction of new system functions without interfering with service. b. What is a process? A process has many definitions that are discussed in the book. A program in execution An instance of a program running on a computer The entity that can be assigned to and executed on a processor A unit of activity characterized by a single sequential thread of execution, a current state, and an associated set of system resources. Stallings mentions that a process consists of three components: An executable program The associated data needed by the program (variables, work space, buffers, etc.) The execution context of the program The glossary defines the term process as: “A program in execution. A process is controlled and scheduled by the operating system. Same as task.”