Basic Function of Computer

Basic Function of Computer.

                 

A general purpose computer has four main components: the arithmetic logic unit (ALU), the control unit, the memory, and the input and output devices (collectively termed I/O).

1. Control unit
2. Arithmetic/logic unit (ALU)
3. Memory
4. Input/output (I/O)
5. Multitasking
6. Multiprocessing
7. Networking and the Internet

Control unit.

The control unit (often called a control system or central controller) manages the computer's various components; it reads and interprets (decodes) the program instructions, transforming them into a series of control signals which activate other parts of the computer. The control system's function is as follows—note that this is a simplified description, and some of these steps may be performed concurrently or in a different order depending on the type of CPU:

1. Read the code for the next instruction from the cell indicated by the program counter.
2. Decode the numerical code for the instruction into a set of commands or signals for each of the other systems.
3. Increment the program counter so it points to the next instruction.
4. Read whatever data the instruction requires from cells in memory (or perhaps from an input device). The location of this required data is typically stored within the instruction code.
5. Provide the necessary data to an ALU or register.
6. If the instruction requires an ALU or specialized hardware to complete, instruct the hardware to perform the requested operation.
7. Write the result from the ALU back to a memory location or to a register or perhaps an output device.
8. Jump back to step (1). 

Arithmetic/logic unit (ALU).

The ALU is capable of performing two classes of operations: arithmetic and logic. The set of arithmetic operations that a particular ALU supports may be limited to

·         adding

·         subtracting

·         might include multiplying

·         dividing,

·         trigonometry functions (sine, cosine, etc.)

·         square roots.

Some can only operate on whole numbers (integers) whilst others use floating point to represent real numbers.

Logic operations involve Boolean logic: AND, OR, XOR and NOT. These can be useful both for creating complicated conditional statements and processing boolean logic.

Memory.

Magnetic core memory was the computer memory of choice throughout the 1960s, until it was replaced by semiconductor memory. A computer's memory can be viewed as a list of cells into which numbers can be placed or read. Each cell has a numbered "address" and can store a single number. In almost all modern computers, each memory cell is set up to store binary numbers in groups of eight bits (called a byte). Each byte is able to represent 256 different numbers (2^8 = 256); either from 0 to 255 or −128 to +127.

Input/output (I/O).

Hard disk drives are common storage devices used with computers. I/O is the means by which a computer exchanges information with the outside world Devices that provide input or output to the computer are called peripherals. On a typical personal computer, peripherals include input devices like the keyboard and mouse, and output devices such as the display and printer. Hard disk drives, floppy disk drives and optical disc drives serve as both input and output devices. Computer networking is another form of I/O.

Multitasking.

While a computer may be viewed as running one gigantic program stored in its main memory, in some systems it is necessary to give the appearance of running several programs simultaneously. This is achieved by multitasking i.e. having the computer switch rapidly between running each program in turn.

Multiprocessing.

Some computers are designed to distribute their work across several CPUs in a multiprocessing configuration, a technique once employed only in large and powerful machines such as supercomputers, mainframe computers and servers. Multiprocessor and multi-core (multiple CPUs on a single integrated circuit) personal and laptop computers are now widely available, and are being increasingly used in lower-end markets as a result.

 Networking and the Internet.

Computers have been used to coordinate information between multiple locations.

Basic Computer Structure.

Logical Structure of a computer includes:

1.  BIOS (The Basic Input Output System)
2.  CPU (The Processor)
3.  Memory / RAM (Temporary Storage)
4.  Hard Disk (Permanent Storage)
5.  Input / Output Device
6.  Communication Channel (Eg. USB)
7.  Bus (High Speed Internal Communication)
8.  Other Add-on Device…

Example of a Computer Structure.

               

BIOS.

• Basic Input Output System
• Store all the parameter before the OS Load
• (Example are Hard Disk Size, Memory
• Speed, Turn on or turn off the build in device
• such as Sound Card, USB, printer etc)
• Usually stored in Flash Memory

Identify the Component - CPU.

• Central Processing Unit
• It is the core of a computer.
• Responsible for all the calculation and part of the video.
• Usually in the Speed of GHz
• 1G around 1,000 MHz
• 1M = 1Million Instruction / second
• Some Expensive CPU have more build in memory (Cache

Memory / RAM Memory.

• RAM – Random Access Memory
• Act as a temporary Storage.
• EDO > SDRAM > DDR > DDR2
• All data stored in memory are volatile.(Need electricity to keep the data)
• Memory Size is around 256M / 512M /1G / 2G per memory module
• Basic Configuration is around 512M RAM

Hard Disk (ATA / SATA / SCSI).

• Used to stored data permanently.
• Different Type of Hard Disk Size (3.5”, 2.5”, 1.8”, Micro Drive)
• Different Interface : ATA / SATA /SCSI (Speed : ATA < SATA < SCSI)
• Different Speed (Mechanical) (4,200rpm / 5,400rpm / 7,200rpm / 10,000 rpm )
• Different Build in Memory Size (2M / 8M / 16M etc)
• Different Capacity (80G to 500G or even 1T)

Small Size Hard Disk are more popular as they are portable size

Main Board / Mother Board (MB).

Provide a platform to connecting all the devices. (Keyboard / Mouse / Power / CPU / Memory / Hard       Disk / Floppy Disk / Display Card etc)

Many Main Board has already build in Sound Card / Network Card or even display card.

I/O Device & Interface.

• ATA / SATA /SCSI (For Hard Disk)
• Parallel Port or LPT Port (For Printer)
• COM Port (For Modem)
• RJ45 Socket (For Network)
• PS/2 (For Keyboard / Mouse)
• D-Sub / DVI (For Monitor)
• USB (All compatible device)

 Power Supply.

• Power Supply Convert the A.C. Voltage to Lower D.C. Voltage which is suitable for Computer.
• Power Supply can be classified by their loading (Watt).
• Different type of socket for different device.

 Case.

• Case is used to place the main board and the power supply.
• Most case have external USB connection.

Layer Technology of Computer Architecture.

OS -Level.

               

An Operating System is the layer between the hardware and software, as in 

An Operating System is responsible for the following functions.

• Device management using device drivers
• Process management using processes and threads
• Inter-process communication
• Memory management
• File systems

In addition, all operating systems come with a set of standard utilities. The utilities allow common tasks to be performed such as

• being able to start and stop processes .
• being able to organize the set of available applications .
• organize files into sets such as directories .
• view files and sets of files .
• edit files.
• rename, copy, delete files .
• communicate between processes .

Instruction set.

An instruction set, or instruction set architecture (ISA), is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O. An ISA includes a specification of the set of opcodes (machine language), and the native commands implemented by a particular processor.

Instruction types.

Some operations available in most instruction sets include.

Data handling and Memory operations.

Set a register (a temporary "scratchpad" location in the CPU itself) to a fixed constant value move data from a memory location to a register, or vice versa. This is done to obtain the data to perform a computation on it later, or to store the result of a computation. Read and write data from hardware devices

Arithmetic and Logic.

               

add, subtract, multiply, or divide the values of two registers, placing the result in a register perform bitwise operations, taking the conjunction and disjunction of corresponding bits in a pair of registers, or the negation of each bit in a register compare two values in registers (for example, to see if one is less, or if they are equal)

Control flow.

             

branch to another location in the program and execute instructions there conditionally branch to another location if a certain condition holds indirectly branch to another location, but save the location of the next instruction as a point to return to (a call)

Complex instructions.

Some examples of "complex" instructions include:

• saving many registers on the stack at once
• moving large blocks of memory
• complex and/or floating-point arithmetic (sine, cosine, square root, etc.)
• performing an atomic test-and-set instruction
• instructions that combine ALU with an operand from memory rather than a register

Microarchitecture.

                

In computer engineering, microarchitecture (sometimes abbreviated to µarch or uarch), also called computer organization, is the way a given instruction set architecture (ISA) is implemented on a processor. A given ISA may be implemented with different microarchitectures. Implementations might vary due to different goals of a given design or due to shifts in technology. Computer architecture is the combination of microarchitecture and instruction set design.

Microarchitectural concepts.

In general, all CPUs, single-chip microprocessors or multi-chip implementations run programs by performing the following steps:

1. Read an instruction and decode it
2. Find any associated data that is needed to process the instruction
3. Process the instruction
4. Write the results out

 DLD Level.

Digital electronics represent signals by discrete bands of analog levels, rather than by a continuous range. All levels within a band represent the same signal state. Relatively small changes to the analog signal levels due to manufacturing tolerance, signal attenuation or parasitic noise do not leave the discrete envelope, and as a result are ignored by signal state sensing circuitry. A digital circuit is often constructed from small electronic circuits called logic gates that can be used to create combinational logic. Each logic gate represents a function of boolean logic. A logic gate is an arrangement of electrically controlled switches, better known as transistors.

Device Level.

In computing, input/output, or I/O, refers to the communication between an information processing system (such as a computer), and the outside world, possibly a human, or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it. The term can also be used as part of an action; to "perform I/O" is to perform an input or output operation. I/O devices are used by a person (or other system) to communicate with a computer. For instance, a keyboard or a mouse may be an input device for a computer, while monitors and printers are considered output devices for a computer. Devices for communication between computers, such as modems and network cards, typically serve for both input and output.

Solid State Physics.

                      

Solid-state physics. is the study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state physics studies how the large-scale properties of solid materials result from their atomic-scale properties. Thus, solid-state physics forms the theoretical basis of materials science. It also has direct applications, for example in the technology of transistors and semiconductors.