Cmsc 335 Operation Systems

CmSc 335 Operation Systems

Homework 01, due 09/07Solution

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 / CPU Registers
300 / 3005 / 300 / PC
301 / 5940 / AC
302 / 7006 / 3005 / IR
940 / 0002 / I/O Device
005 / 0003

#2. Execute : AC is loaded with the content of I/O device 5. PC is incremented.

Memory / CPU Registers
300 / 3005 / 301 / PC
301 / 5940 / 0003 / AC
302 / 7006 / 3005 / IR
940 / 0002 / 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 / CPU Registers
300 / 3005 / 301 / PC
301 / 5940 / 0003 / AC
302 / 7006 / 5940 / IR
940 / 0002 / I/O Device
005 / 0003

#4. Execute: The content of AC is added to the content of location 940. The result is in AC. PC is incremented

Memory / CPU Registers
300 / 3005 / 302 / PC
301 / 5940 / 0005 / AC
302 / 7006 / 5940 / IR
940 / 0002 / I/O Device
005 / 0003

#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 / CPU Registers
300 / 3005 / 302 / PC
301 / 5940 / 0005 / AC
302 / 7006 / 7006 / IR
940 / 0002 / I/O Device
005 / 0003

#6. Execute: The content of AC is stored into I/O device 6. PC is incremented.

Memory / CPU Registers
300 / 3005 / 303 / PC
301 / 5940 / 0005 / AC
302 / 7006 / 7006 / IR
940 / 0002 / I/O Device
005 / 0003
006 / 0005

1. Describe the evolution of operating systems (300 – 500 words)

See Section 2.2 p.52

1. Read Chapter 2 and give answers to the following questions (Review questions 2.1 and 2.4 on p. 103):

1. 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.

1. 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.”