The system unit is one of the four main hardware components of a computer. It is usually a rectangular container within which other important internal hardware components can be found. Some of the components in the system unit are; Random Access Memory (RAM),Compact Disc-Read Only Memory (CD-ROM),Hard disk, Motherboard,Fan,Processor or Central Processing Unit (CPU),Power Supply and Floppy Disk Drive.
The system unit also has other components like the Universal Serial Bus (USB) ports, power button, cables, video and sound cards.
Components of the system unit and their functions
The motherboard is the main internal hardware component of the system unit. The board is called ‘mother’ because it has all the connectors to the other hardware components of the computer system. This means that all input and output (I/O) devices have their connectors on the motherboard. It has a socket for holding the Central Processing Unit (CPU) or processor with heat sinks and fan mounting location(s) very close to the socket due to the huge amount of heat produced by the CPU (especially high speed CPU) during its operations. It also holds a slot for the main memory, a slot for video or graphics card and a backup battery.
CPU or Processor
The CPU is a hardware component responsible for all operations that is carried out in the computer’s system which is why most computer users refer to it as the brain of the computer and it is held on the motherboard by a slot. The CPU or processor has two main components which are the control unit (CU) and the arithmetic logic unit (ALU). The CU extracts instructions from the memory and executes them in order to control input and output devices while the ALU carries out the arithmetic and logical processes. The speed of a processor is measured in megahertz(MHz) or gigahertz(GHz).
Random Access Memory (RAM)
RAM is the main memory of the computer system whose main function is to store data temporary. It allows data to be accessed easily by the CPU based on the fact that data is accessed randomly (in no specific order). It also speeds up the computer’s operations because of its ability to allow random access to data. The bigger(not in physical shape but in capacity) the RAM, the faster the access to data by the CPU. RAM is volatile, meaning it works or stores data while the computer is still running and loses all data when the computer goes off. The RAM in combination with the CPU and the hard disk is the computer’s major source of speed. A computer can use more than one RAM depending on its user’s preference but limited to the number of memory slots on the motherboard.
Hard disk or Hard drive
The major storage device of the computer system is the hard disk or Hard drive. Unlike the RAM that stores data temporary, the hard drive stores information, files and other documents permanently as its main function and also allows the retrieval of data but it is non-volatile(data is not loss when the computer goes off). Operating system and application software (apps) are installed on the hard drive. The amount of data a hard drive can hold depends on its capacity. The capacity of the hard drives I have seen so far ranges from 20gigabytes(20GB) to 2terabytes(2TB). Most of the modern system units or chassis can contain two hard drives where one can be used as ‘master'(primary) Hard drive; the one onto which the operating system is installed, and the other as ‘slave'(secondary) Hard drive; on which documents and other files can be stored in oder not to overload the primary hard drive to avoid slowing down of the system. The secondary hard drive also serves as a backup in case the primary hard drive crushes.
Basically, computers come with two fans in the system unit or chassis, sometimes three. One CPU fan, one case fan and sometimes, one hard drive fan. A manufacturer can also decide to put in more than one CPU fan or case fan. During operations by the computer the CPU produces a lot of heat and heat could always cause damage to your computer, that is why the CPU fan is put in place to keep the CPU under the required temperature. The case fan is to keep the system unit cooled. The CPU is not the only source of heat but the environment around the system unit especially when temperature is been raised very high by sunshine. The hard drive does not produce as much heat as the CPU so in some system units you may not even see the hard drive fan but some also do have. Therefore, all computer fans’ prime function is to cool down and maintain a conducive temperature within the system unit for smooth operations.
Compact disc(CD) and digital versatile disc (DVD) are storage devices onto which certain amount of audio files, data and other computer files can be stored. Videos can also be stored on them as well. CD-ROM can hold about 700MB of data while DVD-ROM can hold about 4.7GB of data. CD and DVD drives’ functions are to read whatever data has been stored on CDs and DVDs respectively. A DVD drive can read a CD but a CD drive cannot read DVD. There are other drives like the CD-R drive; it can read and write a CD-R, DVD-R drive; it can read and write a CD-R and DVD-R, CD-RW drive; it can read, write, erase and re-write a CD-RW. There is also a DVD-RW drive which can also read, write, erase and re-write a DVD-RW and a CD-RW as well.
Power supply unit (PSU)
Just as any electronic device needs electrical power to function, so as the system unit’s components. But the components do not work with the power from your wall socket so the computer power supply unit receives the alternating current (AC) and converts it to a controlled direct current (DC) for the components to function. (Somewhat good life scenario; a newly born baby can not eat any heavy food so the mother has to eat all the heavy foods for the nutrients to be changed to breast milk for her baby.)
Floppy disk drive
This is an internal hardware component in the system unit positioned closer to the CD-ROM drive and its main function is to read and write from or on a floppy disk or diskette. Though a lot of the modern computers are manufactured without a floppy disk drive but the old computers still have one and can be used.
The USB ports allow the computer user to connect USB items to the system unit to be explored, the power button is used to turn on the system unit, cables are used to connect the components to each other, video or graphics card and sound card enable the computer to play videos and sounds respectively.