Basic elements of laptop System and Instruction Execution Cycle

A laptop system consists of assorted hardware elements. every element plays a particular role in laptop system. These elements are interconnected to every different in such how in order that the pc will perform its functions.  Processor:  Processor is that the main element of a laptop system. It controls the operations of the pc and co-ordinates the opposite elements of the pc. It performs all the functions in keeping with the program directions. It decodes and executes the directions. it's thoufht-about the brain of the pc. It contains variety of special-purpose registers and Arithmetic Logic Unit (ALU). A modem laptop system consists of 1 or additional processors. When there's only 1 processor in an exceedingly laptop system, it's usually called the Central Processing Unit (CPU).  Main Memory:  Programs and information should be loaded into the most -memory of the pc before their execution. the most a part of operating system is additionally loaded into the most memory throughout booting method of the pc. the most memory, could be a temporary storage of the pc. Main memory is additionally called primary memory. If the pc is shutdown or power is suddenly cut-off, all data, programs and operating system are cleared from the memory. the info and programs are permanently stored on the secondary storage device (hard disk, CD-ROM, Tape etc.).

   I/O Modules:  I/O module is an electronic element. it's conjointly called I/O controller or controller devices. the info or program directions are moved between the pc and its external devices through I/O module. every I/O device (such as secondary storage communication equipments, and I/O devices etc.) has its own I/O module (or device controller), that is needed for communication between device and processor. It conjointly controls the I/O operations of the I/O devices. for instance, disk controller exchanges information between disk and processor. The processor writes and reads information to and from disk through disk controller.  In some cases, the I/O module exchanges information directly between main memory and I/O device. In such case, the processor grants the authority to an I/O module to write down and skim information to and from the memory. For this purpose, the I/O module problems scan or write commands to memory.  System Bus:  A system bus is an electrical path. the info and command signals are communicated between the pc elements through bus. for instance, information is communicated between main memory, processor and I/O module through the bus.

   The CPU is connected to any or all different elements of laptop through the system bus The CPU controls and co-ordinates different elements of the pc by sending command signals. The system bus is additional divided into information bus, management bus and Address bus.  Instruction Execution Cycle: for each instruction of the program, the management unit (a a part of CPU) carries out 3 basic operations, called the machine cycle. it's conjointly referred to as instruction cycle.  1.Fetch Instruction: the method of transferring a program instruction from memory to CPU is termed fetch instruction. The CPU gets a program instruction from main memory for taking action on it.  2. Decode Instruction: the method of decoding the instruction in order that the pc will perceive is termed Decode Instruction. Actually, during this step, {the necessary|the needed|the mandatory} circuits are activated that are required to execute the instruction.  3. Execute Instruction: the method of taking action on the decoded instruction is termed Execute Instruction. once decoding the instruction, the processor executes the instruction by using the activated circuits. The results of the execution are written back to main memory or CPU registers.