Sang Doan

Hardware, CPU, Input, Output, Memory, Storage.

A computer system has 2 parts: hardware and software.


Hardware includes the physical components in a computer. There are three main parts: 

  1. System Unit: This part is a box which contains the electric components of the computer. There are processor, memory chips, power supply, and hard drives.
  2. Monitor: Monitor connects with the system unit by a wire. It displays everything that you work.
  3. Keyboard: This equipment is a typewriter. It is used to type the command or enter the information in the computer. A computer is also required some equipment such as mouse, modem, printer, etc. They are also hardware.
Input: input devices such as keyboard or mouse enter data or commands. They control the signals to the CPU.
  • Keyboard: input the texts or characters by putting the button. It is connected to the system unit.
  • Mouse: This is the pointing device to control and work with the computer.

In the computer system, keyboard and mouse are the basic parts. Besides, input devices are also microphone (input sound into the system), scanner (input the image, handwriting, or an object), joystick (gaming controller)…

Output: show the data in the computer. User inputs the data into the system, and output device such as monitor will display the data.

The output devices are also speaker (display the sound from the computer system), printer (print out the document or image which user put in the computer)

CPU: Central Processing Unit. CPU is one of the most essential elements of the computers. It is referred to as a brain of the computer. CPU is a data processing circuit according to previously established programs. It is a complex integrated circuit includes millions of transistors on a small circuit board. 

Two major manufactures are Intel and AMD.

The first CPU of Intel was introduced in November 1971. It was 4004 (4bit).

 AMD introduced the first CPU in 1975. It was Am2901 (4bit).

Sources of historical data and information for computer processors - Link

Memory: RAM (random access memory) is the main memory to store the changed information, and the current information used in the computer.  There are also devices that use some kind of RAM as a secondary storage device (secondary storage).

RAM memory is called random access because it has the properties: the time taken to read or write operations for each memory cell is the same, whether at any location in memory. Each of the RAM memory cell has an address. Typically, each memory cell is one byte (8 bits), but the system can read out or written to multiple bytes (2, 4, 8 bytes).

Information in RAM is temporary; they will disappear when the power is off.

There are two different RAM: Static RAM (SRAM) and Dynamic RAM (DRAM). DRAM is slower than SRAM but it’s cheaper.

SDRAM (Synchronous Dynamic RAM): SDRAM includes SDR, DDR, DDR2, and DDR3


o PC-66: 66 MHz bus.
o PC-100: 100 MHz bus.
o PC-133: 133 MHz bus.


 DDR-200: PC-1600. 100 MHz bus with 1600 MB/s bandwidth.
o DDR-266: PC-2100. 133 MHz bus with 2100 MB/s bandwidth.
o DDR-333: PC-2700. 166 MHz bus with 2667 MB/s bandwidth.
o DDR-400: PC-3200. 200 MHz bus with 3200 MB/s bandwidth.


o DDR2-400: PC2-3200. 100 MHz clock, 200 MHz bus with 3200 MB/s bandwidth.
o DDR2-533: PC2-4200. 133 MHz clock, 266 MHz bus with 4267 MB/s bandwidth.
o DDR2-667: PC2-5300. 166 MHz clock, 333 MHz bus with 5333 MB/s bandwidth.
o DDR2-800: PC2-6400. 200 MHz clock, 400 MHz bus with 6400 MB/s bandwidth.

RDRAM (Rambus Dynamic RAM): It’s not much faster than SDRAM, but it is very expensive. So many computers don’t use it.

Capacity: RAM is measured in MB and GB. Usually, RAM is designed with the capacity of 8, 16,32, 64, 128, 256, 512 MB​​, 1 GB, 2 GB ... RAM capacity of as large as possible for the system, but not all systems hardware and operating systems support the large amount of RAM. A hardware system of personal computer only supports up to 4 GB, and some operating systems (such as 32 ​​bit version of Windows XP) only support up to 4GB. Now, the hardware of the computer (main-board) can support up to 16GB with 64 bit operating system. Actually, 64 bit operating system can support up to 128GB RAM.   

Historical Data and Information for DRAM and Other Memory - Link



Storage is where contains data in the computer. The data will be stored on the disc. When user accesses to the data, the reader or writer will receive the information and transmit to the processor located on the circuit of the HDD. Hard disk drive is the device for storing the computer data even when the computer is idle or off.

Initially, the hard drive is designed to operate in the computer. With the development of technology, hard drives have smaller size and greater capacity. Today, hard drives are also used in electronic devices as digital music player, camera, camcorders, DVD players, etc. 

Now, there are two type of hard disk drives: internal hard drive and external hard drive. Internal hard drive is installed inside the system unit. External hard drive is referred to as portable hard drive. It can be removed easily. 

IBM introduced the first hard drive in 1956.

Actuator Arm:  is responsible for stabilizing the motor rotation speed and control actuator arm. It is a robot arm, which moves on the disk surface to put the head on the position to write or read data.

Read / write head: read data from disk or write data to disk.

Platter: circular disk is coated with a magnetic. Disk can be used on both sides (up and bottom)

Cache: a temporary storage data when accessing data. HDD with larger cache has higher speed to access data.

Cover: to prevent the damage and withstand the minor collision, there is a box to protect the above devices. 

The popular standard hard drive interface:

Ultra ATA 
Fibre Channel 
Ultra SCSI 
Ultra160 SCSI 
Ultra320 SCSI 
Serial ATA 

ATA is popular on the personal computer. Besides, there are SCSI and Fibre Channel with higher speed, and they are used for file server.

Information for Computer Hard Disk Drives and Other Storage - Link

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