Lesson-1.pdf

CSci 123: OPERATING SYSTEMS  Objectives: 1. To provide a grand tour of the major operating systems components. 2. To provide coverage of basic computer system organization.  Lesson 1: Introduction to Operating Systems An operating system is a program that acts as an intermediary betwee...

CSci 123: OPERATING SYSTEMS  Objectives: 1. To provide a grand tour of the major operating systems components. 2. To provide coverage of basic computer system organization.  Lesson 1: Introduction to Operating Systems An operating system is a program that acts as an intermediary between a user of a computer and the computer hardware. The purpose of an operating system is to provide an environment in which a user can execute programs. The primary goal of an operating system is thus to make the computer system convenient to use. A secondary goal is to use the computer hardware in an efficient manner.  Introduction to Operating Systems In brief, an operating system is the set of programs that controls a computer. Some examples of operating systems are UNIX, Mach, MS-DOS, MS-Windows, Windows/NT, OS/2 and MacOS. An operating system is an important part of almost every computer system. A computer system can be divided roughly into four components: the hardware, the operating system, the application programs and the users (Figure 1.1).  Computer System Components 1. Hardware - Provides basic computing resources (CPU, memory, I/O devices). 2. Operating System - Controls and coordinates the use of hardware among application programs. 3. Application Program - Solve computing problems of users (compilers, database systems, video games, business programs such as banking software). 4. User - People, machines, other computers Objectives of Operating Systems To hide details of hardware by creating abstraction. To allocate resources to processes (Manage resources). Provide a pleasant and effective user interface.  History of Operating Systems An English mathematician Charles Babbage designed the first true digital computer. He spent most of his life trying to build his “analytical engine” but never got it working properly because it was purely mechanical, and the technology of his day could not produced the required wheels, gears and cogs to the high precision that he needed. Obviously, the analytical engine did not have an OS. Babbage realized that he would need software for his analytical engine, so he hired Ada Lovelace. She became the world’s first programmer. The programming language Ada is named after her. Analytical Engine Ada Lovelace  History of Operating Systems First Generation: Vacuum tubes and Plug boards The first ones used mechanical relays but were very slow, with cycle times measured in seconds. Relays were later replaced by vacuum tubes. These machines were enormous but they were still million times slower than even the cheapest personal computers available today. By the early 1950s, the routine had improved somewhat with the introduction of punched cards. It was now possible to write programs on cards and read them instead of using plug boards. Computer Plug-Board - Univac, Model 1004, circa1965 A 12-row/80-column IBM punched card  History of Operating Systems The 1955 – 1965: Second Generation Transistors and Batch System The introduction of the transistors in the mid-1950s changed the picture radically. Computers became reliable enough that they could be manufactured and sold to paying customers with the expectation that they would continue to function long enough to get some useful work done. These machines, now called mainframes, were locked away in specially air conditioned computer rooms, with staff of professional operators to run them. To run a job (i.e. a program or set of programs), a programmer would first write the program on paper (in FORTRAN or assembler), then punch it on cards.  History of Operating Systems He would then bring the card deck down to the input room and hand it to one of the operators and wait until the output was ready. When the computer finished the job, an operator would go over to the printer and tear off the output and carry it over to the output room, so that the programmer could collect it later. Much computer time was wasted while operators were walking around the machines.  History of Operating Systems The 1965 – 1980: Third Generation ICs and Multiprogramming The systems of the 1960's were also batch processing systems, but they were able to take better advantage of the computer's resources by running several jobs at once. 1980 – present: Fourth Generation Personal Computers With the development of LSI (Large Scale Integration) circuits, chips, operating system entered in the personal computer and the workstation age. Microprocessor technology evolved to the point that it becomes possible to build desktop computers as powerful as the mainframes of the 1970s.