The document discusses the history and structure of early operating systems. It describes how operating systems have evolved through different generations from using valves to integrated circuits. It then provides details on the three main functions of an operating system: coordinating hardware, managing files, and handling failures. The document also describes two common structures for organizing operating systems - the modular and microkernel structures.

1. HISTORIA DE LOS SISTEMAS OPERATIVOS ANTIGUOS<br />Operating Systems, like the hardware of computers, have suffered a series of revolutionary changes called generations. In the case of Hardware, generations havebeen marked by great advances in the components used, from valves (first generation)transistor (second generation), to integrated circuits (third generation), a largeintegrated circuits and very large scale (fourth generation). Each successive generation of hardware has been accompanied by substantial reductions in cost, size, heatemission and energy consumption, and significant increases in speed and capacity<br />966470186055<br />Operating System (OS), basic software that controls a computer. Operating system isitself a computer program. However, it is a very special, perhaps the most complex andimportant in a computer. The OS wakes up and makes the computer recognize theCPU, memory, keyboard, video system and disk drives. It also provides the facility forusers to communicate with the computer and serves as a platform from which to runapplication programs.The operating system consists of software that allows access and perform basicoperations on a personal computer or computer system in general. The most popular operating systems are: AIX (IBM), GNU / Linux, HP-UX (HP), MacOS (Macintosh),Solaris (SUN Microsystems), different variants of BSD Unix (FreeBSD, OpenBSD .. .),and Windows in its various forms (from Microsoft).When you turn on a computer, the first thing it does is to carry out a self-called self test(Power On Self Test, POST). During POST, the computer identifies your memory, yourrecords, your keyboard, your video system and any other device connected to it. Thenext thing the computer does is look for an OS to boot (boot).The operating system has three major functions: coordinates and manipulates thecomputer hardware such as memory, printers, disk drives, keyboard or mouse,organizes the files on various storage devices like floppy disks, hard disks , CDs or tapes, and manages the hardware failures and data loss.<br />Modular structure.Also called monolithic systems. This arrangement is by far the most common, it could receive the subtitle of quot;
big mess.quot;
The structure is that there is not any structure. The operating system is written as a collection of procedures, each of which can call each other every time they needed. When using this technique, each procedure of the system has a well defined interface in terms of parameters and results, and each is free to call any other, if the latter provides a useful calculation for the former. But even in such systems can have at least some structure. Services (system calls) that provides the operating system is asked to place in well-defined parameters, such as registers or the stack, then execute a special trap called quot;
call centerquot;
or quot;
call supervisor. quot;
This statement changes the machine's user mode and kernel mode transfers control to the operating system, which is shown at the event (1) in Figure 1. The operating system then examines the parameters of the call, to determine which one is desired, as shown in the event (2) in Figure 1. Then, the operating system looks at a table that contains the entry k a pointer to the procedure performed by the k-th system call. This operation is shown in (3) of Figure 1, identifies the service procedure, which is called. Finally, the system call terminates and control returns to user program.Figure 1. The way it should be a system call: (1) the user program is attracted to the core. (2) the operating system determines the number of service requested. (3) the operating system locates and calls the procedure for the service. (4) control returns to user program.This organization suggests a basic organization of the operating system:1 .- a main program that calls the procedure of the requested service.2 .- a set of service procedures that perform system calls.3 .- a set of utility procedures that help the service procedure.In this model, for each system call service there is a procedure that takes care of him.Utility procedures do things necessary for various service procedures, for example to find the data user programs. The following figure illustrates the procedure of three layers:(To see the missing chart click on the top menu quot;
Download Jobquot;
)Figure 2. A simple structure model for a monolithic system.(To see the missing chart click on the top menu quot;
Download Jobquot;
)Microkernel structure.The core functions of an OS are controlled by the kernel (kernel) while the user interface is controlled by the environment (shell). For example, the most important part of the DOS is a program named quot;
COMMAND.COMquot;
This program has two parts. The kernel, which is kept in memory at all times, containing the machine code to handle low-level hardware management for other programs that need these services, and Part Two of the COMMAND.COM shell, which is the interpreter commandThe low-level OS and command interpretation functions are separate, so you can keep running the DOS kernel, but using a different user interface. This is exactly what happens when you load Microsoft Windows, which takes the place of the shell, replacing the command line interface with a graphical user interface. There are many quot;
shellsquot;
different in the market, eg NDOS (Norton DOS), XTG, PCTOOLS, or even the same OS from MS-DOS version 5.0 included a Shell called DOS SHELL.<br />