Memory Management and Primary (Main) Memory ● Provides direct access storage for CPU ● Processes must be in main memory to execute and OS must: ● Mechanicsand Keep track of memory in use and Keep track of unused (“free”) memory and Protect memory space and Allocate, deallocate space for processes and Swap processes: memory disk ● Policies and Decide when to load each process into memory and Decide how much memory space to allocate each process and Decide when a process should be removed from memory. One OS Structure: Large Kernel and The kernel is the protected part of the OS that runs in kernel mode ● Critical OS data structures and device registers are protected from user programs ● Can use privileged instructions signals terminals character I/O files swapping disk, tape CPU scheduling page replacement sytem services: shells, compilers, printing, network access system calls user programs hardware: terminals, I/O devices, memory machineindependent machinedependent. OS Design Issues and Another approach: layered OS ● Divide OS into layers ● Each layer uses services provided by next lower
The function to be performed by the Arithmetic logic unit (ALU) is specified by the control unit. By outputting the control signals in the proper order, the control unit causes the CPU to properly fetch, decode, and perform every instruction in its instruction
POST: It stands for Power on Self Test. Post checks all the hardware connected to a computer like RAM, hard disk etc and will make sure that the system can run smoothly with the hardware devices. If the POST is a failure the system halts with a beep sound. Now BIOS checks the priority. We can set the boot priority as CD drive or floppy drive.
Advantages of accessing memory through virtual address are as follows: 1. Program will use a contiguous range of virtual addresses in order to access large memory buffer which is not contiguous in physical memory. 2. A program can use a range of virtual addresses to access a memory buffer that is larger than the available physical memory. As and how physical memory becomes small, the memory manager will be the pages of physical memory to a disk file.
There are three types of interrupts: Hardware Interrupts are generated by hardware devices to signal that they need some attention from the OS. They may have just received some data (e.g., keystrokes on the keyboard or an data on the Ethernet card); or they have just completed a task which the operating system has requested, such as transferring data between the hard drive and memory. Software Interrupts are generated by programs when they want to request a system call to be done by the operating system. Traps are generated by the
A Computer is a programmable electronic device designed to accept data, perform prescribed mathematical and logical operations at high speed, and display the results of these operations. Mainframes, desktop and laptop computers, tablets, and smartphones are some of the different types of computers. 2. Here are the Basic Components of a Computer: a) Input Unit - Data and instructions must enter the computer system before any computation can be performed on the supplied data. The input that links the external environment with the computer system performs this task.
Instruction List language (IL) or (IS). - After the program has been written using the ladder language being sent from the PC memory (programming tool) to the program memory in the device (PLC) and includes a translation of the instructions to the machine language accepted by the processor by the translator (Compiler) supplied with the device's software. Programmable device program required for this project was done using a program (WPLsoft2.4), which enables us to design and simulations designed program before sending it to the device (plc) has been design using a temporary internal split time depending on the priorities for action for each line, and is the work of a full cycle time ( four lines) 80 seconds per lamp 20 seconds in green and yellow bulb be done with nested green lamp which works in the last 5 seconds of the work of the green lamp. As for the lamp with the red color shall be done when Extinction green color and be done time 60
Database designers design database diagram, System analysts and programmers design and implement the application program and lastly End users who use application program for organization`s using. D. Procedures This refers to sets of regulation and instruction used to govern the design and uses of the database that written and enforce by Database administrators. Example, procedures are like owner`s manual how to operate and use DBMS properly and efficiently. E. Data Data covers the collection of facts stored in the database. Since data are building blocks of information, it is important to know what data needed into database and how to organize data properly is vital part of database designer`s