Unit 3 - Computer Systems

Logical vs Physical A computer system can be represented in either a logical or physical form Both are useful in understanding Computer Systems theory. Logical Computer System Presentation Unit 3Slide 2

Physical Computer System The actual hardware as seen in real life Contains micro-electronics and physical mechanisms Powered by electricity Very detailed and complex Difficult to fully understand without a working knowledge of electronics. Logical Computer System Presentation Unit 3Slide 3

Physical Computer System Task  What makes up the physical computer system? Logical Computer System Presentation Unit 2Slide 4

Physical Computer System CPU Monitor Keyboard Mouse Printer Logical Computer System Presentation Unit 2Slide 5

Logical Computer System A basic model of a computer system The model is built from a number of different blocks Each block performs a different task All blocks work together to process data into information Model is conceptual – could not be physically the same in real-life Less complex, easier to understand. Logical Computer System Presentation Unit 3Slide 6

Data Flow BTEC Level 2 Dip IT - Unit 3 Computer Systems Data flows around the computer via the form of electrical impulses called bits. A computer can only recognise ‘0’ and ‘1’( Binary Code). All data flows in and out of the Central Processing Unit.

Logical Computer System Logical Computer System Presentation Unit 3Slide 8 CPU Control Unit Input Device Backing Storage Output Device Main Memory ALU Test me!

How the CPU works BTEC Level 2 Dip IT - Unit 3 Computer Systems The Central Processing Unit (CPU) of a computer is the main processor which operates the computer - ie it carries out the instructions of the program being run. The CPU has three main parts... The A.L.U. (Arithmetic and Logic Unit) which performs all the calculations. The Control Unit - which controls the flow of data round the computer by sending out control signals. Memory - which is used to store data.

Basic Diagram of the CPU BTEC Level 2 Dip IT - Unit 3 Computer Systems CU- Control Unit ALU- Arithmetic and Logic Unit Memory

Input Device  A device which lets the user “feed” data into the computer  Converts data into a stream of electronic digital signals  Digital signals will be converted into binary inside the computer  Some sample real-world input devices; keyboard, mouse, light pen, scanner, microphone, camera, motion sensors, biometric devices such as a fingerprint scanner, OMR/OCR readers for direct data capture etc. Logical Computer System Presentation Unit 3Slide 11

Main Memory Stores data before being processed by CPUCPU Stores program being executed by computer Is volatile - when power is removed, data is lost Often called “RAM” - Random Access Memory Stores processed data before it is outputoutput Contents are filled by Input Devices, Backing Storage or the CPUInput DevicesBacking Storage CPU Data that needs to be saved (for future use) is written to the backing storage.backing storage Logical Computer System Presentation Unit 3Slide 12

Backing Storage  Usually non-volatile, although its contents may be deleted  Loads previously stored data into the main memorymain memory  Loads previously written programs into memory for processing by CPUCPU  In the real world may be internal or external  Usually mechanical (eg Hard Drive, CD or DVD Writer) which slows a computer system  Data is usually “read” (loaded) or “written” (saved). Logical Computer System Presentation Unit 3Slide 13

Output Devices Converts processed data, stored in main memory, into a form that can be understood by a human as informationmain memory Some sample real-world output devices; monitor (CRT or TFT/LCD), speakers, printer, plotter, robot, etc. Logical Computer System Presentation Unit 3Slide 14

CPU  CPU is an abbreviation of Central Processing Unit  The CPU is often called the Processor  The CPU is the computer’s brain  The speed of the CPU generally determines the efficiency and power of the computer system  The CPU consists of two sub-systems: The ALU (Arithmetic/Logic Unit) and the Control Unit. The former performs basic calculations and logical comparisons. The latter co-ordinates and runs the computer’s operations. Logical Computer System Presentation Unit 3Slide 15

Activity Complete the worksheet activity by identifying the correct components on the logical computer system model. Logical Computer System Presentation Unit 2Slide 16