### Computer Notes- PROCESSING SYSTEM

PROCESSING SYSTEM

Processing System mediates between the input system and output system, which is process of thinking as done by the computer. Processing Systems includes
 Calculations
 Comparisons
 Decisions

The thinking process in the computer is done by manipulating the digital digits as all information in modern computer is stored as a string of zeros or ones off or on. 1bit= one on or off position 1 byte = 8 bits The entire processing part occurs in the central processing unit of the computer system.

COMPONENTS OF PROCESSING UNITS
Central Processing Unit (CPU) Central Processing Unit or CPU is also known as the brain of computer where entire processing is done. Most of the computers contain one processing chip.

CONTROL UNIT (CU)
This is the part of the computer, which controls the machine cycle. It takes a number of cycles to do even a simple addition of two numbers. It performs the various functions:
 Fetch: It gets an instruction from main memory.
 Decode: It translates it into computer commands.
 Execute: It processes the command.
 Store: It writes the result to main memory.

ARITHMETIC LOGIC UNIT (ALU)
 It is the part, which executes the computer's commands.
 It does either a basic arithmetic operation or the logical comparisons.
 The arithmetic operation may include+ – * /
 The logical comparisons may include > < = not =

Machine Cycle Fetch In this cycle an instruction is fetched from the main memory. Decode In this cycle, the fetched instruction is translated into the computer commands. Execute In this cycle, the command is actually processed. Store In this cycle, the result is written into the main memory. The immense speed of the computer enables it to do millions of such steps in a second.

A memory address holds 1 byte of data where
 1 bit = 0 or 1/on or off
 1 byte = 8 bits
 1 kilobyte = 1024 bytes
 1 megabyte = 1024 kilobytes (K or KB)

PROCESSOR SPEED
 Processor speed is affected by system clock rate.
 The rate of an electronic pulse is used to synchronize processing.
 It is measured in megahertz (MHz) where 1 MHz = 1 million cycles per second or in gigahertz (GHz) where 1 GHz = 1 billion cycles per second

PHYSICAL COMPONENTS OF COMPUTER
The Physical Components of a computer are directly involved in processing. They are
 Microprocessor
 Memory device
 Motherboard

MICROPROCESSOR
 This is a single silicon chip containing CPU, ALU and some memory.
 The microprocessor chip is located on a large circuit board called the main board or motherboard.
 The physical size of a computer chip is very small.

MEMORY DEVICES
They may include Vacuum Tube This is the oldest type that cannot hold up long and generate a lot of heat. Core These are small metal rings that represents on and off. They are relatively slow. Semi Conductor This is integrated circuit on a chip. The modern computers use this for their memory. Motherboards The motherboards have a number of slots for memory and all the slots contain the same size memory board. Connectors This is the slot where cables connect to motherboard for the things like hard drives, floppy drives and CD Rom drives. ISA Slots This board has three slots for the things like video cards, sound cards, internal modems etc. Keyboard Plug This is the slot where the keyboard attaches through the back of computer.

MEMORY SLOTS
 There are four short slots for the semiconductor memory.
 This board has two long slots for a new kind of memory called DIMM DRAM.
 This board can support a maximum of 256 MB of memory.

PCI Slots This board contains four slots for the peripherals like video cards, internal modems, sound cards etc. Power connection This is the slot where power supply connects to the motherboard. Processor Socket This is the slot where the processor plugs into the motherboard.