General Architecture of Digital Computer By: Dr. Yahya Tareq Mr. Riyad basil

General Architecture A digital computer is a machine that can be used to solve problems for people and carrying out the tasks by following the instructions given to it. Basic components of computer system architecture: Computer Hardware: is the collection of physical parts of a computer system, such as computer case, monitor, keyboard, and mouse. It also includes all the parts inside the computer case. Computer Software: Software is a set of instructions for a computer to perform specific operations. Software systems divide into two major classes: System software: Helps run the computer hardware and computer system itself. System software includes operating systems, device drivers, diagnostic tools and more. Application software: Allows users to accomplish one or more tasks. It includes word processing, web browsing and almost any other task for which you might install software.

Units of Measurement for digital information Bit Nibble 0000 Byte 0000 0000 Word 0000 0000 0000 0000 A kilobyte is 210 byte, which is 1024 bytes. A megabyte, or meg as some call it, is 220 bytes. That is a little over 1 million bytes; it is exactly 1,048,576. Moving rapidly up the scale in size, a gigabyte is 230 bytes (over 1 billion), and a terabyte is 240 bytes (over 1 trillion). As an example of how some of these terms are used, suppose that a given computer has 16 megabytes of memory. That would be 16 x 220, or 24 x 220, which is 224. therefor 16 megabytes is 224 bytes.

Inside The Computer Inside The Computer

Inside The Computer Central Processing Unit (CPU): is the computer component that's responsible for interpreting and executing most of the commands from the computer's other hardware and software. Memory RAM: is the physical hardware inside a computer that temporarily stores data, serving as the computer's "working" memory. Memory ROM: is a type of storage medium that permanently stores data on personal computers (PCs) and other electronic devices. Peripheral device: is generally defined as any auxiliary device such as a computer mouse or keyboard that connects to and works with the computer in some way. There are two Types of Peripheral Devices: Input devices, such as a mouse and a keyboard, etc… Output devices, such as a monitor and a printer, etc ….

Peripheral Devices

Inside The CPU Programs reside in the memory unit. The ALU processes the data that is hold in the registers and stores the processed data back in the memory unit. The control unit coordinates the activities of the other three units. It retrieves instructions from programs resident in the MU, and directs the ALU to perform corresponding processing steps.

Basic component of CPU Arithmetic and Logic Unit (ALU): is a digital circuit used to perform arithmetic and logic operations. Control (CU): it directs the operation of the processor. It tells the computer’s memory, ALU, and input/output devices on how to respond to a program’s instructions. Registers: is a fast small storage device used for storing data temporally.

Internal Organization of Computers

System Bus Data Bus: is a bidirectional bus through which data is transmitted from one part of a computer to another and connects all the computer components to the CPU and main memory. Address Bus: is a unidirectional bus used to identify particular location in main memory. Control Bus: carries signals that report the status of various devices and controlling the use of data and address lines which are shared by all computer components.

Brief History of CPU Evaluation of Intel’s Microprocessors Product 4004 8008 8080 8085 8086 8088 80286 30386 80486 Generation First Generation Second generation Third generation Fourth generation Year introduced 1971 1972 1974 1976 1978 1979 1982 1985 1989 Clock rate (MHz) 0.74 0.8 2 - 3 3 - 8 5 - 10 5 - 8 6 - 16 16 - 33 25 - 50 No. transistors 2,300 3,500 4,500 6,500 2,9000 130,000 275,000 1.2 million Physical memory 640 Bytes 16K 64K 1M 16M 4G Internal data bus  4 8 16 32 External data bus Address bus 4 14 20 24 Data type (bits) 8, 16 8,16, 32 8, 16, 32

BRIEF HISTORY OF THE CPU Performance of microprocessor is measured in what are called MIPS, that is how many million instructions they can execute per second. They are measured by running a best program called the “drystone program”.

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