Chapter 1

• Operating system – a computer program that acts as an intermediary/ interface between the user of a computer and the computer hardware.
• Operating system – set of system software routines that sits between the application programs and the hardware.
• Application software needs resource, and os will check if the resources are available and allocate it
• If we remove the OS, there will be a gap in language. User uses human language whereas the hardware uses machine language. And the OS serves as the translator between the two.
• 1. 2 functions of OS -  OS as a virtual machine(physical hardware will be converted to virtual machine to hide technicality) and OS as a Resource Manager (resource allocator)
• 1. Multiplexing -  process of allocating resources to complete a process. 2 types of multiplexing technique is Time Multiplexing and Space Multiplexing
• 1. Time Multiplexing – each different processes are given time to utilize a resource one after the other, one at a time and there will be a concept of queueing. Resources that uses time multiplexing – CPU processing, GPU, Printer, Keyboard
• 1. Space Multiplexing – does not uphold the one at a time policy unlike time multiplexing. Rather, it simultaneously allocated free spaces to all processes that it can accommodate. Resources using space multiplexing – memory space, hard disk space
• 6 components of OS -  user command interface, file manager, memory manager, network manager, device manager, processor manager.
• Memory manager -  focused on the proper allocation of memory resources to competing processes or tasks.
• Processor manager -  deals with the proper scheduling of tasks in utilizing the processor or cpu
• File manager – deals with the organization of files in the computer system
• Device manager – refers to the OS control over peripheral devices
• Network manager – incharge with the sharing issues between computers
• Types of OS – single-user operating systems, multi-user operating systems, real-time operating systems, embedded operating system.
• 1. single-user operating systems – only one user can access the computer system at a time. 2 classification: single task and multi task
• multi-user operating systems – capable of handling demands of different users at the same time
• real-time operating systems – makes use of time as a key parameter for its operation.
• embedded operating system – type of an OS that is implanted or rooted to a special type of device or chip
• Zeroth generation (mechanical computer) – only consists of gears, metals, crank. No operating system. Manual operation. Punch cards are used to program the machine (Jacquard looms technology). Example: Analytical engine of Charles Babbage (Father of  the Modern Computer)
• 1. First Generation (Vacuum tubes and serial processing) – Process : vacuum tubes. Internal memory: magnetic drum. External storage: punched card. Example UNIVAC & ENIAC
• UNIVAC (Universal Automatic Computer) – first commercial computer
• ENIAC (Electronic Numerical Integrator And Computer) – first general-purpose computer
• Resident monitor – performs automatic job sequencing by simply transferring control to the program, less intervention of user
• Control cards – specifically designed to instruct the resident monitor on which program should be selected next for processing
• Problem : cpu idle time, slow i/o devices, solution: off-line processing operation, buffer (temporary storage where data can be stored, input and output buffer using magnetic tapes
• Combining input and output buffer using magnetic disk – SPOOLING (Simultaneous Peripheral Operation Online) overlapping the i/o devices
• 1. User command interface -  aka OS Shell. Provides the user with visual tool for communication purposes. 2 types of interface: command line interface and graphical user interface.
• Second generation (transistors and batch processing) -  Process: transistors. Store instruction: magnetic core memory.
• Third generation (integrated circuits and multiprogramming or multi-tasking)
• Fourth generation (modern operating system) – period for the development of graphical user interface
• 2 most prominent OS Rivals – Apple macintosh and Microsoft windows