devkuma – Computer

Introduction to Computers

kc@example.com (kc kim) — Tue, 01 Nov 2022 00:27:00 +0900

Overview of Computers

kc@example.com (kc kim) — Thu, 23 Dec 2021 09:27:00 +0900

Overview of Computers

An electronic calculator that performs complex operations on behalf of people.
It can store and manage large volumes of data.

Characteristics of Computers

Speed: Computers can process large volumes of data. Modern computers perform billions of arithmetic operations per second.
Reliability: Computers support reliable, error-free processing of large amounts of data. This is essential when computers take over human work.
Accuracy: Thanks to rapid advances in semiconductor technology, computer accuracy continues to improve.
Data preservation: With the development of storage devices for preserving many kinds of data, a significant amount of data can be accumulated and stored in a small space.
Economy: By processing large volumes of data quickly, computers reduce time and cost compared with human work.

PC (Personal Computer)

Early computers were not designed for independent personal use. They were developed for shared purposes and were divided into central computers with central processing units and memory devices, and terminals for users. A PC is a computer developed for independent personal use. It combines the central processing unit, memory, and input/output devices that a computer needs into a single product.

Hardware and Software

Hardware

Hardware means physical devices. A computer contains many kinds of hardware, such as the CPU, memory, disk drives, and input/output devices. These devices operate according to software instructions.

Software

Software means the programs that run on a computer and perform work. Operating systems, games, graphics programs, educational programs, and business programs are examples of software.

Basic Terms

bit and Byte

Computers use digital electrical signals that represent all data as 0s and 1s. Digital data represents information using only two electrical states: “1”, where electricity flows, and “0”, where it does not. This is the bit, the smallest unit of data representation in a computer. In other words, 1 bit can represent only two values: 1 and 0. However, this alone is not enough to convert human characters into computer data. Combining two electrical signals can represent four values: 00, 01, 10, and 11. This still cannot represent human characters sufficiently, so 8 bits are combined. When 8 bits are combined, 256 different data values can be represented. This is called 1 byte. Ultimately, this is the amount of data used to represent one character, such as an English letter. 1 byte consists of 8 bits.

Bus

In a computer, a bus is a transmission path for delivering data. Computers may be classified by the structure of this path. It also refers to the width of data that can be exchanged at one time between the CPU and peripheral devices. It starts with 8 bits and has developed through 16 bits, 32 bits, and 64 bits.

History of Computers

ENIAC, the First Computer

In 1944, Aiken, a professor at Harvard University, built “MARK-1” with sponsorship from IBM. Although “MARK-1” could not be called a true computer, in 1946 Mauchly and Eckert at the University of Pennsylvania developed a military computer used for ballistic tables, weather forecasting, atomic energy calculations, and cosmic ray research. This was ENIAC, which used a decimal system.

ENIAC was made to calculate using vacuum tubes. It had as many as 18,000 vacuum tubes and 6,000 switches, so it was large and very difficult to operate. In addition, because programs were not compatible, changing a program required reconnecting all those switches from the beginning.

EDSAC, the Stored-Program Computer

In 1949, Maurice Wilkes completed EDSAC, the first computer with a stored program. In 1951, a computer called EDVAC, again using the binary system, was developed by von Neumann. IBM also developed UNIVAC 1, which used magnetic tape as auxiliary storage, and installed it at the United States Census Bureau.

Computer Generations

Generation	Years	Central Processing Unit	Main Memory	Programming Language
1st generation	1946-1957	Vacuum tubes	Magnetic drum	Assembler
2nd generation	1958-1964	Transistors	Magnetic core	FORTRAN, COBOL
3rd generation	1965-1974	IC	Magnetic disk	Pascal, BASIC
4th generation	Since the 1970s	LSI	Semiconductor	Modern programming languages
5th generation	Present	VLSI	Semiconductor	Modern programming languages

Structure of a PC

Central Processing Unit (CPU)

It contains a control unit that operates each device in the computer and controls normal operation.
It contains an arithmetic unit that processes various computational data.
It contains registers for temporarily storing data.
It determines computer performance and the type of system.

Input Devices

Devices that receive commands and data from the user. Keyboards and mice are examples.

Output Devices

Devices that deliver the results processed by the computer to the user. Monitors and printers are examples.

Storage Devices

Devices where the operating system and various programs are installed and where data created by users is stored.
Hard disks, CD-ROMs, and CD-RWs are examples.

Peripheral Devices

Devices that are not necessary for basic computer operation and management but are added when needed are called peripheral devices.
They can improve user convenience.
LAN cards, sound cards, mice, printers, and joysticks are examples.

Controllers

Controllers manage smooth data flow between devices and detect errors.
They determine the connection method for peripheral devices.
When implemented as hardware, the term “controller” is used.
When implemented as software, a program installed to operate hardware is called a “driver”.

Central Processing Unit (CPU)

kc@example.com (kc kim) — Mon, 07 Nov 2022 10:45:00 +0900

Central Processing Unit (CPU)

CPU stands for Central Processing Unit.
It contains a control unit that operates each device in the computer and controls normal operation.
It contains an arithmetic unit that processes various computational data.
It contains registers for temporarily storing data.
It contains an arithmetic logic unit and performs computational functions.
It determines computer performance and the type of system.
- It determines the type of computer.
- It determines computer performance.

Execution Unit (EU)
The execution unit is the unit that executes each instruction in a microprocessor.
The execution unit consists of the ALU (Arithmetic Logic Unit), the control unit (CU), and registers.
The ALU performs arithmetic operations, such as addition and comparison, as well as logical operations, and stores intermediate results in registers.

Instruction Unit
The instruction unit controls instructions fetched from memory so that they can be executed correctly by the execution unit.
At this time, the control unit ensures that the ALU and registers operate correctly.

Addressing Unit
The addressing unit creates memory or input/output addresses when the CPU reads data from, or writes data to, memory or input/output devices.

Bus Interface Unit
The bus interface unit connects the microprocessor to the outside through the address, data, and control buses.

Cache Memory

Cache memory is one type of buffer memory temporarily used inside the CPU.

Understanding Cache Memory

A cache is a temporary storage device located between two devices with different speeds. It improves the speed of data access between devices and improves processing speed during repeated access.

When cache is not applied

Run a program called TEST.EXE.
Load TEST.EXE from (1) auxiliary storage, such as a hard disk, into (3) main memory.
When the program exits, the program loaded in (3) disappears.
Run the same program again.
The program is loaded from (1) into (3) again. In this case, the user must wait each time while the program is read from (1).

When cache is applied

Run TEST.EXE.
While the program is loaded from (1) into (3), it is also written to (2).
When the program exits, the program loaded in (3) disappears. However, what was stored in (2) is not erased.
Run the same program again.
This time, the program is loaded from (2), not from (1). From the perspective of (3), the same program is being loaded, but the first time it was loaded from slower auxiliary storage. From the second time onward, repeated loading occurs from faster cache memory, which improves speed.

Clock (Operating Frequency)

A clock is a unit that represents CPU speed. A clock refers to the time it takes for a waveform to move once in one second, and CPU speed changes depending on the amount of data processed during that time.
It is written in Hz. In general, the higher the clock value, the faster the performance.
However, if only the clock is raised to improve performance, power consumption increases and heat generation can become severe, so this must also be considered.

Clock and FSB

A clock is an electrical rhythm that oscillates at a fixed cycle and is generated by the motherboard’s clock generator to operate the CPU and other devices. It is expressed in MHz (megahertz).

1 Hz is a clock that oscillates once per second, and a CPU basically processes one instruction per clock.

It is used as a unit for expressing the speed of the CPU and the system.

FSB (Front Side Bus) is another name for the clock generated by the motherboard’s clock generator and supplied to each device. It is also called the external clock. The CPU and devices inside the computer operate according to the clock speed supplied by the clock generator. However, the CPU does not use the supplied clock as-is. It uses “clock doubling” to increase that speed several times before using it.

Core

A core is the central part of the processing circuit built into the central processing unit. In the past, when computers were not as widespread, it was natural for one CPU to have one core.
However, dual-core processors with two cores appeared in 2005, making multi-core processors popular in general PCs. Later, processors with four, six, and even eight cores appeared.

A dual-core processor can reduce work that a single core would have processed in two steps to one step. Therefore, it has the advantage of improving overall processing efficiency.

Virtualization Support

Virtualization support, simply put, means running another operating system inside an operating system. For example, it is a technology that allows Linux or another operating system to run inside Windows, just as a program runs after Windows starts. Intel CPUs support virtualization under the name “VT-x”, and AMD CPUs under the name “AMD-V”. To build a cloud environment with servers, it is essential to check whether the CPU supports virtualization.

Types of CPUs

CPU Types by Data Processing Capacity

Classification according to the amount of data that can be processed simultaneously.
The width of the bus, which is the path that transfers data.
8 bits is the minimum unit of data processed by a computer.
Development progressed from 8088 (8-bit) to 80286 (16-bit), 80386 (32-bit), and Pentium (64-bit).

ARM

Licensed products from companies such as Apple and Samsung.
ARM chips are small, generate less heat, and consume less power. They do not require a cooling fan. However, they have tended to be limited to specialized uses.

Main Memory (Memory) ROM, RAM

kc@example.com (kc kim) — Wed, 30 Nov 2022 00:21:00 +0900

Main Memory (Memory)

Overview of ROM/ROM BIOS

ROM (Read Only Memory) is a read-only memory element and is used in computers to store the BIOS.
The Basic Input/Output System is the basic program for operating a computer.
It contains basic information about each device in the computer and diagnoses each device.
When the power is turned on, it starts the computer and diagnoses itself. The BIOS must never be erased, so it is stored in ROM, which is non-volatile memory.

RAM

RAM (Random Access Memory) is also called RWM (Read Write Memory). Because all information stored inside disappears when the computer is turned off, it is called volatile memory. RAM is a memory device that allows data to be read and written freely. Since it is volatile, all contents in memory are erased when power is cut off.

How DRAM Stores Data
DRAM (Dynamic RAM) stores data using the principle that capacitors store electricity. What we call data in a computer is actually the flow of electrical signals. Computer data is represented by 1s and 0s, which respectively mean a state where electricity flows and a state where it does not. If this electrical state can be maintained, that is storage. The most common media for storing electricity are electronic components called capacitors or batteries.
For example, to store the data 10101010, prepare eight capacitors and store the data by charging those corresponding to 1 and not charging those corresponding to 0. This stores the data 10101010. DRAM is a device that stores data using this capacitor principle.
However, electricity once stored in a capacitor or battery does not last forever. Even when it is not used, natural discharge occurs, and after a certain amount of time data is lost. Therefore, RAM performs a refresh, or recharge, operation to maintain its current state before data is lost. When the computer is turned off, RAM cannot perform this refresh, so the data is lost. In other words, it has volatile properties. DRAM has long been used as an element for computer main memory because its principle is simple and it is easy to manufacture, but it is now being improved into new forms because refresh operations increase waiting time.

Types of RAM

Category	DRAM	SRAM
Refresh	Required	Not required
Access speed	Slow	Fast
Circuit structure	Simple	Complex
Integration density	High	Low
Price	Cheap	Expensive
Use	Main memory	Cache memory
Comparison of DRAM and SRAM

Types of DRAM

SDRAM
SDRAM is DRAM whose clock speed is synchronized with the microprocessor. Clock speed synchronization helps increase the number of instructions the processor can execute within a given time.

DDR SDRAM
DDR (Double Data Rate) memory SDRAM is the name given to memory that can transfer twice as much data as previous SDRAM. DDR memory has two standards, PC2100 and PC1600, but they do not actually operate at 2100 MHz and 1600 MHz respectively. DDR SDRAM operating on a 100 MHz memory bus has a speed around PC200, and when operating on a 133 MHz bus, around PC266.

DDR2 SDRAM
DRAM that improves the operating speed of DDR SDRAM by two times.

Rambus DRAM
Rambus DRAM is DRAM connected through the Rambus Channel, a data transfer bus developed by the American company Rambus. This channel uses a 9-bit bus and transfers data synchronized with a 250 MHz clock.