Course Name: Computer Application Topic: Central Processing Unit (CPU) LECTURE Course Name: Computer Application Topic: Central Processing Unit (CPU)

Central Processing Unit (CPU) The Central Processing Unit s also called Processor. This is the brain or heart of the computer equipment. The CPU carries out the calculations for the program and controls the other components of the system. The CPU (Central Processing Unit) is often manufactured by a company called Intel, and it is one of the most important components within your computer. It determines how fast your computer will run and the CPU speed is measured by its GHz speed. Thus, a 4 GHz CPU is much faster than say a 1 GHz CPU. It is the CPU which performs all the calculations within the computer, when running programs such as word-processors, spreadsheets and databases.

Central Processing Unit (CPU) Functions of a Central Processing Unit It performs arithmetic operations as well as controls the input, output and storage units. The CPU is controlled by a list of software instructions. Software instructions are initially stored in secondary memory storage device such as a hard disk, floppy disk, CD-ROM, or magnetic tape. These instructions are then loaded onto the computer’s main memory. When a program is executed, instructions flow from the main memory to the CPU through the bus. The instructions are then decoded by a processing unit called the instruction decoder that interprets and implements the instructions.

Central Processing Unit (CPU) The CPU has three major components. Arithmetic and Logic Unit (ALU) Control Unit (CU) Registers (internal memory) CPU consists of the following features: CPU is considered as the brain of the computer. CPU performs all types of data processing operations. It stores data, intermediate results and instructions(program). It controls the operation of all parts of computer.

Arithmetic Logic Unit The arithmetic and logic unit (ALU) is the part of CPU where actual computations take place. The arithmetic and logic units in computers are capable of performing addition, subtraction, division and multiplication as well as some logical operations. The ALU also performs logic functions such as AND, OR and NOT. The ALU functions are directly controlled by the control unit. The ALU has logic circuits that can compare two numbers to determine if they are equal or if one number is greater than storage locations called storage registers for storing numbers used in calculations and for storing the results of calculations. To perform a calculation or logical operation, number is transferred from primary storage to storage registers in the ALU. These numbers are sent to the appropriate arithmetic or logic circuit. The results are sent back to the storage registers. The results are transferred from the storage registers to primary storage.

Central Processing Unit (CPU) ALU(Arithmetic Logic Unit) It interprets the instructions fetched from the main memory of the computer, sends the control signals to the devices involved in the execution of the instructions. While performing these operations the ALU takes data from the temporary storage area inside the CPU named registers. They are high-speed memories which hold data for immediate processing and results of the processing.

Central Processing Unit (CPU) This unit consists of two subsections namely Arithmetic section Logic Section Arithmetic Section Arithmetic Logic Unit of a computer system is the place where the actual executions of instructions takes place during processing operation. Function of arithmetic section is to perform arithmetic operations like addition, subtraction, multiplication and division. Function of logic section is to perform logic operations such as comparing, selecting, matching and merging of data.

Central Processing Unit (CPU) Control Unit (CU) Control Unit of computer system manages and coordinates the operations of all other components of the computer system. This unit controls the operations of all parts of computer but does not carry out any actual data processing operations. Functions of this unit are: It is responsible for controlling the transfer of data and instructions among other units of a computer. It manages and coordinates all the units of the computer. It obtains the instructions from the memory, interprets them, and directs the operation of the computer. It communicates with Input/output devices for transfer of data or results from storage. It does not process or store data.

Control Unit The control Unit controls the whole computer system by performing the following functions: directs and coordinates all operation called for by the program activates the appropriate circuits necessary for inputs and output devices. Causes the entire computer system to operate in an automatic manner. The control unit contains a temporary storage location called an instruction register for storing the instruction being executed. It also contains circuits called the instruction decoder which analyse the instruction register and cause it to be executed. The control unit executes each instruction by following the same basic sequence of steps: he next instruction in the program is retrieved for primary storage and stored in the instruction register the instruction is sent to the instruction decoder where it is analysed. The decoder sends signals to the ALU, primary storage, I/O devices, and secondary storage, that cause the actions required by the instructions to be performed. These steps are repeated for each instruction in the program until all instructions have been executed.

Control unit repeats four basic operations: Fetch - obtain program instruction or data item from memory Decode-translate instruction into commands Execute -carry out command Store - write result to memory

Registers Special memory units, called registers, are used to hold information on a temporary basis as the instructions are interpreted and executed by the CPU and Registers are part of the CPU (not main memory) of a computer. Temporary storage area that holds data and instruction Stores location from where instruction was fetched Stores instruction while it is being decoded Stores data while ALU processes it Stores results of calculation

What are common components inside the system unit Processor Memory Module Expansion Cards Sound card Modem card Video card Network interface card Ports and Connectors What is the System Board Man Circuit board in System Unit Contains Chips, Integrated Circuits and transistors It is also called motherboard