Computer and Its Components Introduction.pptx

Computer and its Components with explanations

1. Computer and Its Components

2. Computers Mainframes and super computers are the biggest computers – million dollar machines, as big as a refrigerator or bigger. An example is the IBM model 390 .

3. Computers cont. Minicomputers are large, powerful machines which are often found at the centre of networks of “dumb” terminals and PC’s. For example, IBM’s AS/400. A definition that was used in the past, was that minicomputers cost between $10,000 and $100,000.

4. Computers cont. Workstations are very powerful user machines. They have the capacity to execute technical/scientific programs and calculations, and typically use a UNIX variant or Windows NT as their operating system. Workstations used to be equipped with powerful RISC processors, like Digital Alpha, Sun Sparc or MIPS(million instructions per second), but today workstations can be configured with one or more of Intel’s more powerful CPU’s.

5. Computers cont. The PC is the baby of the family: Small, cheap, mass-produced computers which typically run Windows and which are used for standard programs which can be purchased anywhere.

6. The Four Components of a Computer Central Processing Unit Memory Input/Output System Computer Interconnection

7. The Central Processing Unit:

8. The CPU: Processor Organization To understand the organization of the CPU, let us consider the requirements placed on the CPU, the things that it must do : The CPU has two main parts: 1. Control Unit Oversees all the activities inside the computer and monitors the execution of the programs Performs the following: Obtains instructions from the primary storage unit Transmits direction to the appropriate components of the computer system ordering them to perform the required data processing operations:

9. The CPU 2. Arithmetic Logic Unit (ALU) Performs all computations and all logic operations. Accumulator – place where results are placed in registers Logic operation – comparing two pieces of data, either alphabetic or numeric

10. MAKING THE PROCESSOR WORK Machine language native tongue for Computers Instructions represented in the computers by strings of binary digits Machine Cycle The total of instruction time and the execution time

11. MAKING THE PROCESSOR WORK cont. Actions take place during Machine Cycle Instruction Time Fetch Instruction . The next machine language instruction to be executed is retrieved or fetched from RAM memory and loaded to the instruction register in the CU. Decode Instruction . Th e instruction is decoded and interpreted.

12. MAKING THE PROCESSOR WORK cont. Actions take place during Machine Cycle Execution Time Execution Instruction . Using whatever processor resources (arithmetic and logic unit) are needed, the instruction is executed Place results in memory . Th e instruction are placed in the appropriate memory position or the accumulator.

13. Control Unit: CU Part of the hardware that is in-charge Directs the computer system to execute stored program instructions Must communicate with memory and ALU Sends data and instructions from secondary storage to memory as needed

14. Arithmetic Logic Unit Executes all arithmetic and logical operations Arithmetic operations Addition , subtraction , multiplication, division Logical operations Compare numbers, letters, or special characters Tests for one of three conditions Equal-to condition Less-than condition Greater-than condition

15. Data Storage and the CPU Two types of storage: Primary storage (memory) Stores data temporarily CPU refers to it for both program instructions and data Secondary storage Long-term storage Stored on external medium, such as a disk

16. The CPU and Memory CPU cannot process data from disk or input device It must first reside in memory Control unit retrieves data from disk and moves it into memory Items sent to ALU for processing Control unit sends items to ALU, then sends back to memory after processing Data and instructions held in memory until sent to an output or storage device or program is shut down

17. Registers Special-purpose High-speed Temporary storage Located inside CPU Instructio n

18. Memory Also known as primary storage and main memory Often expressed as random-access memory (RAM) Not part of the CPU Holds data and instructions for processing Stores information only as long as the program is in operation

19. Memory Addresses Each memory location has an address A unique number, much like a mailbox. May contain only one instruction or piece of data. When data is written back to memory, previous contents of that address are destroyed. Referred to by number Programming languages use a symbolic (named) address, such as Hours or Salary.

20. Memory Components Semiconductor Memory RAM and ROM Flash Memory

21. Semiconductor Memory Used by most modern computers Reliable , inexpensive, and compact Volatile : requires continuous electric current If the current is interrupted, data is lost Complementary Metal Oxide Semiconductor (CMOS) Retains information when power is shut down Used to store information needed when the computer boots

22. Random Access Memory Data can be accessed randomly Types : Static RAM (SRAM) Dynamic RAM (DRAM) Packaged on circuit boards Single in-line memory modules (SIMMS) Dual in-line memory modules (DIMMS)

23. Read-Only Memory Contains programs and data permanently recorded into memory at the factory Cannot be changed by user Not volatile: contents do not disappear when power is lost Programmable ROM (PROM) chips Some instructions on chip can be changed

24. Flash Memory Nonvolatile RAM Used in cellular phones, digital cameras, and some handheld computers Flash memory chips resemble credit cards Smaller than disk drive and require less power